Merge tag 'pull-10.1-maintainer-june-2025-020725-1' of https://gitlab.com/stsquad/qemu into staging

Maintainer updates for June (gitlab, semihosting, plugins, virtio-gpu)

 - mark s390x runner system tests as allow_fail
 - build semihosting once
 - add register write support to plugins
 - add virtual memory write support to plugins
 - add harder memory read/write support to plugins
 - add patcher plugin and tests
 - re-stock virtio-gpu MAINTAINERS
 - fix context init for Venus fences

* tag 'pull-10.1-maintainer-june-2025-020725-1' of https://gitlab.com/stsquad/qemu:
  virtio-gpu: support context init multiple timeline
  MAINTAINERS: add Akihiko and Dmitry as reviewers
  MAINTAINERS: add myself to virtio-gpu for Odd Fixes
  plugins: Update plugin version and add notes
  plugins: Add patcher plugin and test
  tests/tcg: Remove copy-pasted notes and from i386 and add x86_64 system tests to tests
  plugins: Add memory hardware address read/write API
  plugins: Add memory virtual address write API
  plugins: Add enforcement of QEMU_PLUGIN_CB flags in register R/W callbacks
  plugins: Add register write API
  gdbstub: Expose gdb_write_register function to consumers of gdbstub
  semihosting/uaccess: Compile once
  semihosting/uaccess: Remove uses of target_ulong type
  tests/functional: Add PCI hotplug test for aarch64
  gitlab: mark s390x-system to allow failures

Conflicts:
  tests/functional/meson.build

  Context conflict with commit 7bc86ccbb5 ("tests/functional: test
  device passthrough on aarch64"), keep both changes to
  tests_aarch64_system_thorough[].

.gitlab-ci.d/custom-runners/ubuntu-22.04-s390x.yml

@@ -31,7 +31,9 @@ ubuntu-22.04-s390x-all-system:
  timeout: 75m
  rules:
  - if: '$CI_PROJECT_NAMESPACE == "qemu-project" && $CI_COMMIT_BRANCH =~ /^staging/'
+   allow_failure: true
  - if: "$S390X_RUNNER_AVAILABLE"
+   allow_failure: true
  script:
  - mkdir build
  - cd build

MAINTAINERS

@@ -2091,6 +2091,12 @@ S: Supported
 F: include/hw/pci/pcie_doe.h
 F: hw/pci/pcie_doe.c
 
+ARM PCI Hotplug
+M: Gustavo Romero <gustavo.romero@linaro.org>
+L: qemu-arm@nongnu.org
+S: Supported
+F: tests/functional/test_aarch64_hotplug_pci.py
+
 ACPI/SMBIOS
 M: Michael S. Tsirkin <mst@redhat.com>
 M: Igor Mammedov <imammedo@redhat.com>
@@ -2680,7 +2686,10 @@ F: hw/display/ramfb*.c
 F: include/hw/display/ramfb.h
 
 virtio-gpu
-S: Orphan
+M: Alex Bennée <alex.bennee@linaro.org>
+R: Akihiko Odaki <odaki@rsg.ci.i.u-tokyo.ac.jp>
+R: Dmitry Osipenko <dmitry.osipenko@collabora.com>
+S: Odd Fixes
 F: hw/display/virtio-gpu*
 F: hw/display/virtio-vga.*
 F: include/hw/virtio/virtio-gpu.h

accel/tcg/plugin-gen.c

@@ -117,10 +117,20 @@ static TCGv_i32 gen_cpu_index(void)
 static void gen_udata_cb(struct qemu_plugin_regular_cb *cb)
 {
     TCGv_i32 cpu_index = gen_cpu_index();
+    enum qemu_plugin_cb_flags cb_flags =
+        tcg_call_to_qemu_plugin_cb_flags(cb->info->flags);
+    TCGv_i32 flags = tcg_constant_i32(cb_flags);
+    TCGv_i32 clear_flags = tcg_constant_i32(QEMU_PLUGIN_CB_NO_REGS);
+    tcg_gen_st_i32(flags, tcg_env,
+           offsetof(CPUState, neg.plugin_cb_flags) - sizeof(CPUState));
     tcg_gen_call2(cb->f.vcpu_udata, cb->info, NULL,
                   tcgv_i32_temp(cpu_index),
                   tcgv_ptr_temp(tcg_constant_ptr(cb->userp)));
+    tcg_gen_st_i32(clear_flags, tcg_env,
+           offsetof(CPUState, neg.plugin_cb_flags) - sizeof(CPUState));
     tcg_temp_free_i32(cpu_index);
+    tcg_temp_free_i32(flags);
+    tcg_temp_free_i32(clear_flags);
 }
 
 static TCGv_ptr gen_plugin_u64_ptr(qemu_plugin_u64 entry)
@@ -173,10 +183,20 @@ static void gen_udata_cond_cb(struct qemu_plugin_conditional_cb *cb)
     tcg_gen_ld_i64(val, ptr, 0);
     tcg_gen_brcondi_i64(cond, val, cb->imm, after_cb);
     TCGv_i32 cpu_index = gen_cpu_index();
+    enum qemu_plugin_cb_flags cb_flags =
+        tcg_call_to_qemu_plugin_cb_flags(cb->info->flags);
+    TCGv_i32 flags = tcg_constant_i32(cb_flags);
+    TCGv_i32 clear_flags = tcg_constant_i32(QEMU_PLUGIN_CB_NO_REGS);
+    tcg_gen_st_i32(flags, tcg_env,
+           offsetof(CPUState, neg.plugin_cb_flags) - sizeof(CPUState));
     tcg_gen_call2(cb->f.vcpu_udata, cb->info, NULL,
                   tcgv_i32_temp(cpu_index),
                   tcgv_ptr_temp(tcg_constant_ptr(cb->userp)));
+    tcg_gen_st_i32(clear_flags, tcg_env,
+           offsetof(CPUState, neg.plugin_cb_flags) - sizeof(CPUState));
     tcg_temp_free_i32(cpu_index);
+    tcg_temp_free_i32(flags);
+    tcg_temp_free_i32(clear_flags);
     gen_set_label(after_cb);
 
     tcg_temp_free_i64(val);
@@ -210,12 +230,22 @@ static void gen_mem_cb(struct qemu_plugin_regular_cb *cb,
                        qemu_plugin_meminfo_t meminfo, TCGv_i64 addr)
 {
     TCGv_i32 cpu_index = gen_cpu_index();
+    enum qemu_plugin_cb_flags cb_flags =
+        tcg_call_to_qemu_plugin_cb_flags(cb->info->flags);
+    TCGv_i32 flags = tcg_constant_i32(cb_flags);
+    TCGv_i32 clear_flags = tcg_constant_i32(QEMU_PLUGIN_CB_NO_REGS);
+    tcg_gen_st_i32(flags, tcg_env,
+           offsetof(CPUState, neg.plugin_cb_flags) - sizeof(CPUState));
     tcg_gen_call4(cb->f.vcpu_mem, cb->info, NULL,
                   tcgv_i32_temp(cpu_index),
                   tcgv_i32_temp(tcg_constant_i32(meminfo)),
                   tcgv_i64_temp(addr),
                   tcgv_ptr_temp(tcg_constant_ptr(cb->userp)));
+    tcg_gen_st_i32(clear_flags, tcg_env,
+           offsetof(CPUState, neg.plugin_cb_flags) - sizeof(CPUState));
     tcg_temp_free_i32(cpu_index);
+    tcg_temp_free_i32(flags);
+    tcg_temp_free_i32(clear_flags);
 }
 
 static void inject_cb(struct qemu_plugin_dyn_cb *cb)

gdbstub/gdbstub.c

@@ -535,7 +535,7 @@ int gdb_read_register(CPUState *cpu, GByteArray *buf, int reg)
     return 0;
 }
 
-static int gdb_write_register(CPUState *cpu, uint8_t *mem_buf, int reg)
+int gdb_write_register(CPUState *cpu, uint8_t *mem_buf, int reg)
 {
     GDBRegisterState *r;
 

hw/display/virtio-gpu-virgl.c

@@ -970,6 +970,15 @@ void virtio_gpu_virgl_process_cmd(VirtIOGPU *g,
     }
 
     trace_virtio_gpu_fence_ctrl(cmd->cmd_hdr.fence_id, cmd->cmd_hdr.type);
+#if VIRGL_VERSION_MAJOR >= 1
+    if (cmd->cmd_hdr.flags & VIRTIO_GPU_FLAG_INFO_RING_IDX) {
+        virgl_renderer_context_create_fence(cmd->cmd_hdr.ctx_id,
+                                            VIRGL_RENDERER_FENCE_FLAG_MERGEABLE,
+                                            cmd->cmd_hdr.ring_idx,
+                                            cmd->cmd_hdr.fence_id);
+        return;
+    }
+#endif
     virgl_renderer_create_fence(cmd->cmd_hdr.fence_id, cmd->cmd_hdr.type);
 }
 
@@ -983,6 +992,11 @@ static void virgl_write_fence(void *opaque, uint32_t fence)
          * the guest can end up emitting fences out of order
          * so we should check all fenced cmds not just the first one.
          */
+#if VIRGL_VERSION_MAJOR >= 1
+        if (cmd->cmd_hdr.flags & VIRTIO_GPU_FLAG_INFO_RING_IDX) {
+            continue;
+        }
+#endif
         if (cmd->cmd_hdr.fence_id > fence) {
             continue;
         }
@@ -997,6 +1011,29 @@ static void virgl_write_fence(void *opaque, uint32_t fence)
     }
 }
 
+#if VIRGL_VERSION_MAJOR >= 1
+static void virgl_write_context_fence(void *opaque, uint32_t ctx_id,
+                                      uint32_t ring_idx, uint64_t fence_id) {
+    VirtIOGPU *g = opaque;
+    struct virtio_gpu_ctrl_command *cmd, *tmp;
+
+    QTAILQ_FOREACH_SAFE(cmd, &g->fenceq, next, tmp) {
+        if (cmd->cmd_hdr.flags & VIRTIO_GPU_FLAG_INFO_RING_IDX &&
+            cmd->cmd_hdr.ctx_id == ctx_id && cmd->cmd_hdr.ring_idx == ring_idx &&
+            cmd->cmd_hdr.fence_id <= fence_id) {
+            trace_virtio_gpu_fence_resp(cmd->cmd_hdr.fence_id);
+            virtio_gpu_ctrl_response_nodata(g, cmd, VIRTIO_GPU_RESP_OK_NODATA);
+            QTAILQ_REMOVE(&g->fenceq, cmd, next);
+            g_free(cmd);
+            g->inflight--;
+            if (virtio_gpu_stats_enabled(g->parent_obj.conf)) {
+                trace_virtio_gpu_dec_inflight_fences(g->inflight);
+            }
+        }
+    }
+}
+#endif
+
 static virgl_renderer_gl_context
 virgl_create_context(void *opaque, int scanout_idx,
                      struct virgl_renderer_gl_ctx_param *params)
@@ -1031,11 +1068,18 @@ static int virgl_make_context_current(void *opaque, int scanout_idx,
 }
 
 static struct virgl_renderer_callbacks virtio_gpu_3d_cbs = {
+#if VIRGL_VERSION_MAJOR >= 1
+    .version             = 3,
+#else
     .version             = 1,
+#endif
     .write_fence         = virgl_write_fence,
     .create_gl_context   = virgl_create_context,
     .destroy_gl_context  = virgl_destroy_context,
     .make_current        = virgl_make_context_current,
+#if VIRGL_VERSION_MAJOR >= 1
+    .write_context_fence = virgl_write_context_fence,
+#endif
 };
 
 static void virtio_gpu_print_stats(void *opaque)

include/exec/gdbstub.h

@@ -124,6 +124,20 @@ const GDBFeature *gdb_find_static_feature(const char *xmlname);
  */
 int gdb_read_register(CPUState *cpu, GByteArray *buf, int reg);
 
+/**
+ * gdb_write_register() - Write a register associated with a CPU.
+ * @cpu: The CPU associated with the register.
+ * @buf: The buffer that the register contents will be set to.
+ * @reg: The register's number returned by gdb_find_feature_register().
+ *
+ * The size of @buf must be at least the size of the register being
+ * written.
+ *
+ * Return: The number of written bytes, or 0 if an error occurred (for
+ * example, an unknown register was provided).
+ */
+int gdb_write_register(CPUState *cpu, uint8_t *mem_buf, int reg);
+
 /**
  * typedef GDBRegDesc - a register description from gdbstub
  */

include/hw/core/cpu.h

@@ -368,6 +368,7 @@ typedef struct CPUNegativeOffsetState {
     GArray *plugin_mem_cbs;
     uint64_t plugin_mem_value_low;
     uint64_t plugin_mem_value_high;
+    int32_t plugin_cb_flags;
 #endif
     IcountDecr icount_decr;
     bool can_do_io;

include/qemu/plugin.h

@@ -209,6 +209,21 @@ void qemu_plugin_user_prefork_lock(void);
  */
 void qemu_plugin_user_postfork(bool is_child);
 
+enum qemu_plugin_cb_flags tcg_call_to_qemu_plugin_cb_flags(int flags);
+
+static inline void qemu_plugin_set_cb_flags(CPUState *cpu,
+                                            enum qemu_plugin_cb_flags flags)
+{
+    assert(cpu);
+    cpu->neg.plugin_cb_flags = flags;
+}
+
+static inline enum qemu_plugin_cb_flags qemu_plugin_get_cb_flags(void)
+{
+    assert(current_cpu);
+    return current_cpu->neg.plugin_cb_flags;
+}
+
 #else /* !CONFIG_PLUGIN */
 
 static inline void qemu_plugin_add_opts(void)

include/qemu/qemu-plugin.h

@@ -65,11 +65,18 @@ typedef uint64_t qemu_plugin_id_t;
  *
  * version 4:
  * - added qemu_plugin_read_memory_vaddr
+ *
+ * version 5:
+ * - added qemu_plugin_write_memory_vaddr
+ * - added qemu_plugin_read_memory_hwaddr
+ * - added qemu_plugin_write_memory_hwaddr
+ * - added qemu_plugin_write_register
+ * - added qemu_plugin_translate_vaddr
  */
 
 extern QEMU_PLUGIN_EXPORT int qemu_plugin_version;
 
-#define QEMU_PLUGIN_VERSION 4
+#define QEMU_PLUGIN_VERSION 5
 
 /**
  * struct qemu_info_t - system information for plugins
@@ -254,9 +261,6 @@ typedef struct {
  * @QEMU_PLUGIN_CB_NO_REGS: callback does not access the CPU's regs
  * @QEMU_PLUGIN_CB_R_REGS: callback reads the CPU's regs
  * @QEMU_PLUGIN_CB_RW_REGS: callback reads and writes the CPU's regs
- *
- * Note: currently QEMU_PLUGIN_CB_RW_REGS is unused, plugins cannot change
- * system register state.
  */
 enum qemu_plugin_cb_flags {
     QEMU_PLUGIN_CB_NO_REGS,
@@ -871,7 +875,8 @@ struct qemu_plugin_register;
 /**
  * typedef qemu_plugin_reg_descriptor - register descriptions
  *
- * @handle: opaque handle for retrieving value with qemu_plugin_read_register
+ * @handle: opaque handle for retrieving value with qemu_plugin_read_register or
+ *          writing value with qemu_plugin_write_register
  * @name: register name
  * @feature: optional feature descriptor, can be NULL
  */
@@ -893,6 +898,51 @@ typedef struct {
 QEMU_PLUGIN_API
 GArray *qemu_plugin_get_registers(void);
 
+/**
+ * qemu_plugin_read_register() - read register for current vCPU
+ *
+ * @handle: a @qemu_plugin_reg_handle handle
+ * @buf: A GByteArray for the data owned by the plugin
+ *
+ * This function is only available in a context that register read access is
+ * explicitly requested via the QEMU_PLUGIN_CB_R_REGS flag, if called inside a
+ * callback that can be registered with a qemu_plugin_cb_flags argument. This
+ * function can also be used in any callback context that does not use a flags
+ * argument, such as in a callback registered with
+ * qemu_plugin_register_vcpu_init_cb(), except for callbacks registered with
+ * qemu_plugin_register_atexit_cb() and qemu_plugin_register_flush_cb().
+ *
+ * Returns the size of the read register. The content of @buf is in target byte
+ * order. On failure returns -1.
+ */
+QEMU_PLUGIN_API
+int qemu_plugin_read_register(struct qemu_plugin_register *handle,
+                              GByteArray *buf);
+
+/**
+ * qemu_plugin_write_register() - write register for current vCPU
+ *
+ * @handle: a @qemu_plugin_reg_handle handle
+ * @buf: A GByteArray for the data owned by the plugin
+ *
+ * This function is only available in a context that register read access is
+ * explicitly requested via the QEMU_PLUGIN_CB_RW_REGS flag, if called inside a
+ * callback that can be registered with a qemu_plugin_cb_flags argument. This
+ * function can also be used in any callback context that does not use a flags
+ * argument, such as in a callback registered with
+ * qemu_plugin_register_vcpu_init_cb(), except for callbacks registered with
+ * qemu_plugin_register_atexit_cb() and qemu_plugin_register_flush_cb().
+ *
+ * The size of @buf must be at least the size of the requested register.
+ * Attempting to write a register with @buf smaller than the register size
+ * will result in a crash or other undesired behavior.
+ *
+ * Returns the number of bytes written. On failure returns 0.
+ */
+QEMU_PLUGIN_API
+int qemu_plugin_write_register(struct qemu_plugin_register *handle,
+                              GByteArray *buf);
+
 /**
  * qemu_plugin_read_memory_vaddr() - read from memory using a virtual address
  *
@@ -916,20 +966,118 @@ bool qemu_plugin_read_memory_vaddr(uint64_t addr,
                                    GByteArray *data, size_t len);
 
 /**
- * qemu_plugin_read_register() - read register for current vCPU
+ * qemu_plugin_write_memory_vaddr() - write to memory using a virtual address
  *
- * @handle: a @qemu_plugin_reg_handle handle
- * @buf: A GByteArray for the data owned by the plugin
+ * @addr: A virtual address to write to
+ * @data: A byte array containing the data to write
  *
- * This function is only available in a context that register read access is
- * explicitly requested via the QEMU_PLUGIN_CB_R_REGS flag.
+ * The contents of @data will be written to memory starting at the virtual
+ * address @addr.
  *
- * Returns the size of the read register. The content of @buf is in target byte
- * order. On failure returns -1.
+ * This function does not guarantee consistency of writes, nor does it ensure
+ * that pending writes are flushed either before or after the write takes place,
+ * so callers should take care to only call this function in vCPU context (i.e.
+ * in callbacks) and avoid depending on the existence of data written using this
+ * function which may be overwritten afterward.
+ *
+ * Returns true on success and false on failure.
  */
 QEMU_PLUGIN_API
-int qemu_plugin_read_register(struct qemu_plugin_register *handle,
-                              GByteArray *buf);
+bool qemu_plugin_write_memory_vaddr(uint64_t addr,
+                                   GByteArray *data);
+
+/**
+ * enum qemu_plugin_hwaddr_operation_result - result of a memory operation
+ *
+ * @QEMU_PLUGIN_HWADDR_OPERATION_OK: hwaddr operation succeeded
+ * @QEMU_PLUGIN_HWADDR_OPERATION_ERROR: unexpected error occurred
+ * @QEMU_PLUGIN_HWADDR_OPERATION_DEVICE_ERROR: error in memory device
+ * @QEMU_PLUGIN_HWADDR_OPERATION_ACCESS_DENIED: permission error
+ * @QEMU_PLUGIN_HWADDR_OPERATION_INVALID_ADDRESS: address was invalid
+ * @QEMU_PLUGIN_HWADDR_OPERATION_INVALID_ADDRESS_SPACE: invalid address space
+ */
+enum qemu_plugin_hwaddr_operation_result {
+    QEMU_PLUGIN_HWADDR_OPERATION_OK,
+    QEMU_PLUGIN_HWADDR_OPERATION_ERROR,
+    QEMU_PLUGIN_HWADDR_OPERATION_DEVICE_ERROR,
+    QEMU_PLUGIN_HWADDR_OPERATION_ACCESS_DENIED,
+    QEMU_PLUGIN_HWADDR_OPERATION_INVALID_ADDRESS,
+    QEMU_PLUGIN_HWADDR_OPERATION_INVALID_ADDRESS_SPACE,
+};
+
+/**
+ * qemu_plugin_read_memory_hwaddr() - read from memory using a hardware address
+ *
+ * @addr: The physical address to read from
+ * @data: A byte array to store data into
+ * @len: The number of bytes to read, starting from @addr
+ *
+ * @len bytes of data is read from the current memory space for the current
+ * vCPU starting at @addr and stored into @data. If @data is not large enough to
+ * hold @len bytes, it will be expanded to the necessary size, reallocating if
+ * necessary. @len must be greater than 0.
+ *
+ * This function does not ensure writes are flushed prior to reading, so
+ * callers should take care when calling this function in plugin callbacks to
+ * avoid attempting to read data which may not yet be written and should use
+ * the memory callback API instead.
+ *
+ * This function is only valid for softmmu targets.
+ *
+ * Returns a qemu_plugin_hwaddr_operation_result indicating the result of the
+ * operation.
+ */
+QEMU_PLUGIN_API
+enum qemu_plugin_hwaddr_operation_result
+qemu_plugin_read_memory_hwaddr(uint64_t addr, GByteArray *data, size_t len);
+
+/**
+ * qemu_plugin_write_memory_hwaddr() - write to memory using a hardware address
+ *
+ * @addr: A physical address to write to
+ * @data: A byte array containing the data to write
+ *
+ * The contents of @data will be written to memory starting at the hardware
+ * address @addr in the current address space for the current vCPU.
+ *
+ * This function does not guarantee consistency of writes, nor does it ensure
+ * that pending writes are flushed either before or after the write takes place,
+ * so callers should take care when calling this function in plugin callbacks to
+ * avoid depending on the existence of data written using this function which
+ * may be overwritten afterward. In addition, this function requires that the
+ * pages containing the address are not locked. Practically, this means that you
+ * should not write instruction memory in a current translation block inside a
+ * callback registered with qemu_plugin_register_vcpu_tb_trans_cb.
+ *
+ * You can, for example, write instruction memory in a current translation block
+ * in a callback registered with qemu_plugin_register_vcpu_tb_exec_cb, although
+ * be aware that the write will not be flushed until after the translation block
+ * has finished executing.  In general, this function should be used to write
+ * data memory or to patch code at a known address, not in a current translation
+ * block.
+ *
+ * This function is only valid for softmmu targets.
+ *
+ * Returns a qemu_plugin_hwaddr_operation_result indicating the result of the
+ * operation.
+ */
+QEMU_PLUGIN_API
+enum qemu_plugin_hwaddr_operation_result
+qemu_plugin_write_memory_hwaddr(uint64_t addr, GByteArray *data);
+
+/**
+ * qemu_plugin_translate_vaddr() - translate virtual address for current vCPU
+ *
+ * @vaddr: virtual address to translate
+ * @hwaddr: pointer to store the physical address
+ *
+ * This function is only valid in vCPU context (i.e. in callbacks) and is only
+ * valid for softmmu targets.
+ *
+ * Returns true on success and false on failure.
+ */
+QEMU_PLUGIN_API
+bool qemu_plugin_translate_vaddr(uint64_t vaddr, uint64_t *hwaddr);
 
 /**
  * qemu_plugin_scoreboard_new() - alloc a new scoreboard

include/semihosting/uaccess.h

@@ -15,9 +15,9 @@
 #endif
 
 #include "exec/cpu-common.h"
-#include "exec/cpu-defs.h"
 #include "exec/tswap.h"
 #include "exec/page-protection.h"
+#include "exec/vaddr.h"
 
 /**
  * get_user_u64:
@@ -89,8 +89,8 @@
  *
  * The returned pointer should be freed using uaccess_unlock_user().
  */
-void *uaccess_lock_user(CPUArchState *env, target_ulong addr,
-                        target_ulong len, bool copy);
+void *uaccess_lock_user(CPUArchState *env, vaddr addr,
+                        size_t len, bool copy);
 /**
  * lock_user:
  *
@@ -103,7 +103,7 @@ void *uaccess_lock_user(CPUArchState *env, target_ulong addr,
  *
  * The returned string should be freed using uaccess_unlock_user().
  */
-char *uaccess_lock_user_string(CPUArchState *env, target_ulong addr);
+char *uaccess_lock_user_string(CPUArchState *env, vaddr addr);
 /**
  * uaccess_lock_user_string:
  *
@@ -112,10 +112,10 @@ char *uaccess_lock_user_string(CPUArchState *env, target_ulong addr);
 #define lock_user_string(p) uaccess_lock_user_string(env, p)
 
 void uaccess_unlock_user(CPUArchState *env, void *p,
-                         target_ulong addr, target_ulong len);
+                         vaddr addr, size_t len);
 #define unlock_user(s, args, len) uaccess_unlock_user(env, s, args, len)
 
-ssize_t uaccess_strlen_user(CPUArchState *env, target_ulong addr);
+ssize_t uaccess_strlen_user(CPUArchState *env, vaddr addr);
 #define target_strlen(p) uaccess_strlen_user(env, p)
 
 #endif /* SEMIHOSTING_SOFTMMU_UACCESS_H */

plugins/api.c

@@ -39,6 +39,7 @@
 #include "qemu/main-loop.h"
 #include "qemu/plugin.h"
 #include "qemu/log.h"
+#include "system/memory.h"
 #include "tcg/tcg.h"
 #include "exec/gdbstub.h"
 #include "exec/target_page.h"
@@ -433,6 +434,29 @@ GArray *qemu_plugin_get_registers(void)
     return create_register_handles(regs);
 }
 
+int qemu_plugin_read_register(struct qemu_plugin_register *reg, GByteArray *buf)
+{
+    g_assert(current_cpu);
+
+    if (qemu_plugin_get_cb_flags() == QEMU_PLUGIN_CB_NO_REGS) {
+        return -1;
+    }
+
+    return gdb_read_register(current_cpu, buf, GPOINTER_TO_INT(reg) - 1);
+}
+
+int qemu_plugin_write_register(struct qemu_plugin_register *reg,
+                               GByteArray *buf)
+{
+    g_assert(current_cpu);
+
+    if (buf->len == 0 || qemu_plugin_get_cb_flags() != QEMU_PLUGIN_CB_RW_REGS) {
+        return -1;
+    }
+
+    return gdb_write_register(current_cpu, buf->data, GPOINTER_TO_INT(reg) - 1);
+}
+
 bool qemu_plugin_read_memory_vaddr(uint64_t addr, GByteArray *data, size_t len)
 {
     g_assert(current_cpu);
@@ -453,11 +477,118 @@ bool qemu_plugin_read_memory_vaddr(uint64_t addr, GByteArray *data, size_t len)
     return true;
 }
 
-int qemu_plugin_read_register(struct qemu_plugin_register *reg, GByteArray *buf)
+bool qemu_plugin_write_memory_vaddr(uint64_t addr, GByteArray *data)
 {
     g_assert(current_cpu);
 
-    return gdb_read_register(current_cpu, buf, GPOINTER_TO_INT(reg) - 1);
+    if (data->len == 0) {
+        return false;
+    }
+
+    int result = cpu_memory_rw_debug(current_cpu, addr, data->data,
+                                     data->len, true);
+
+    if (result < 0) {
+        return false;
+    }
+
+    return true;
+}
+
+enum qemu_plugin_hwaddr_operation_result
+qemu_plugin_read_memory_hwaddr(hwaddr addr, GByteArray *data, size_t len)
+{
+#ifdef CONFIG_SOFTMMU
+    if (len == 0) {
+        return QEMU_PLUGIN_HWADDR_OPERATION_ERROR;
+    }
+
+    g_assert(current_cpu);
+
+
+    int as_idx = cpu_asidx_from_attrs(current_cpu, MEMTXATTRS_UNSPECIFIED);
+    AddressSpace *as = cpu_get_address_space(current_cpu, as_idx);
+
+    if (as == NULL) {
+        return QEMU_PLUGIN_HWADDR_OPERATION_INVALID_ADDRESS_SPACE;
+    }
+
+    g_byte_array_set_size(data, len);
+    MemTxResult res = address_space_rw(as, addr,
+                                       MEMTXATTRS_UNSPECIFIED, data->data,
+                                       data->len, false);
+
+    switch (res) {
+    case MEMTX_OK:
+        return QEMU_PLUGIN_HWADDR_OPERATION_OK;
+    case MEMTX_ERROR:
+        return QEMU_PLUGIN_HWADDR_OPERATION_DEVICE_ERROR;
+    case MEMTX_DECODE_ERROR:
+        return QEMU_PLUGIN_HWADDR_OPERATION_INVALID_ADDRESS;
+    case MEMTX_ACCESS_ERROR:
+        return QEMU_PLUGIN_HWADDR_OPERATION_ACCESS_DENIED;
+    default:
+        return QEMU_PLUGIN_HWADDR_OPERATION_ERROR;
+    }
+#else
+    return QEMU_PLUGIN_HWADDR_OPERATION_ERROR;
+#endif
+}
+
+enum qemu_plugin_hwaddr_operation_result
+qemu_plugin_write_memory_hwaddr(hwaddr addr, GByteArray *data)
+{
+#ifdef CONFIG_SOFTMMU
+    if (data->len == 0) {
+        return QEMU_PLUGIN_HWADDR_OPERATION_ERROR;
+    }
+
+    g_assert(current_cpu);
+
+    int as_idx = cpu_asidx_from_attrs(current_cpu, MEMTXATTRS_UNSPECIFIED);
+    AddressSpace *as = cpu_get_address_space(current_cpu, as_idx);
+
+    if (as == NULL) {
+        return QEMU_PLUGIN_HWADDR_OPERATION_INVALID_ADDRESS_SPACE;
+    }
+
+    MemTxResult res = address_space_rw(as, addr,
+                                       MEMTXATTRS_UNSPECIFIED, data->data,
+                                       data->len, true);
+    switch (res) {
+    case MEMTX_OK:
+        return QEMU_PLUGIN_HWADDR_OPERATION_OK;
+    case MEMTX_ERROR:
+        return QEMU_PLUGIN_HWADDR_OPERATION_DEVICE_ERROR;
+    case MEMTX_DECODE_ERROR:
+        return QEMU_PLUGIN_HWADDR_OPERATION_INVALID_ADDRESS;
+    case MEMTX_ACCESS_ERROR:
+        return QEMU_PLUGIN_HWADDR_OPERATION_ACCESS_DENIED;
+    default:
+        return QEMU_PLUGIN_HWADDR_OPERATION_ERROR;
+    }
+#else
+    return QEMU_PLUGIN_HWADDR_OPERATION_ERROR;
+#endif
+}
+
+bool qemu_plugin_translate_vaddr(uint64_t vaddr, uint64_t *hwaddr)
+{
+#ifdef CONFIG_SOFTMMU
+    g_assert(current_cpu);
+
+    uint64_t res = cpu_get_phys_page_debug(current_cpu, vaddr);
+
+    if (res == (uint64_t)-1) {
+        return false;
+    }
+
+    *hwaddr = res | (vaddr & ~TARGET_PAGE_MASK);
+
+    return true;
+#else
+    return false;
+#endif
 }
 
 struct qemu_plugin_scoreboard *qemu_plugin_scoreboard_new(size_t element_size)

plugins/core.c

@@ -15,6 +15,7 @@
 #include "qemu/lockable.h"
 #include "qemu/option.h"
 #include "qemu/plugin.h"
+#include "qemu/qemu-plugin.h"
 #include "qemu/queue.h"
 #include "qemu/rcu_queue.h"
 #include "qemu/rcu.h"
@@ -266,7 +267,9 @@ static void qemu_plugin_vcpu_init__async(CPUState *cpu, run_on_cpu_data unused)
     plugin_grow_scoreboards__locked(cpu);
     qemu_rec_mutex_unlock(&plugin.lock);
 
+    qemu_plugin_set_cb_flags(cpu, QEMU_PLUGIN_CB_RW_REGS);
     plugin_vcpu_cb__simple(cpu, QEMU_PLUGIN_EV_VCPU_INIT);
+    qemu_plugin_set_cb_flags(cpu, QEMU_PLUGIN_CB_NO_REGS);
 }
 
 void qemu_plugin_vcpu_init_hook(CPUState *cpu)
@@ -279,7 +282,9 @@ void qemu_plugin_vcpu_exit_hook(CPUState *cpu)
 {
     bool success;
 
+    qemu_plugin_set_cb_flags(cpu, QEMU_PLUGIN_CB_RW_REGS);
     plugin_vcpu_cb__simple(cpu, QEMU_PLUGIN_EV_VCPU_EXIT);
+    qemu_plugin_set_cb_flags(cpu, QEMU_PLUGIN_CB_NO_REGS);
 
     assert(cpu->cpu_index != UNASSIGNED_CPU_INDEX);
     qemu_rec_mutex_lock(&plugin.lock);
@@ -367,6 +372,7 @@ void plugin_register_dyn_cb__udata(GArray **arr,
     static TCGHelperInfo info[3] = {
         [QEMU_PLUGIN_CB_NO_REGS].flags = TCG_CALL_NO_RWG,
         [QEMU_PLUGIN_CB_R_REGS].flags = TCG_CALL_NO_WG,
+        [QEMU_PLUGIN_CB_RW_REGS].flags = 0,
         /*
          * Match qemu_plugin_vcpu_udata_cb_t:
          *   void (*)(uint32_t, void *)
@@ -396,6 +402,7 @@ void plugin_register_dyn_cond_cb__udata(GArray **arr,
     static TCGHelperInfo info[3] = {
         [QEMU_PLUGIN_CB_NO_REGS].flags = TCG_CALL_NO_RWG,
         [QEMU_PLUGIN_CB_R_REGS].flags = TCG_CALL_NO_WG,
+        [QEMU_PLUGIN_CB_RW_REGS].flags = 0,
         /*
          * Match qemu_plugin_vcpu_udata_cb_t:
          *   void (*)(uint32_t, void *)
@@ -434,6 +441,7 @@ void plugin_register_vcpu_mem_cb(GArray **arr,
     static TCGHelperInfo info[3] = {
         [QEMU_PLUGIN_CB_NO_REGS].flags = TCG_CALL_NO_RWG,
         [QEMU_PLUGIN_CB_R_REGS].flags = TCG_CALL_NO_WG,
+        [QEMU_PLUGIN_CB_RW_REGS].flags = 0,
         /*
          * Match qemu_plugin_vcpu_mem_cb_t:
          *   void (*)(uint32_t, qemu_plugin_meminfo_t, uint64_t, void *)
@@ -473,7 +481,9 @@ void qemu_plugin_tb_trans_cb(CPUState *cpu, struct qemu_plugin_tb *tb)
     QLIST_FOREACH_SAFE_RCU(cb, &plugin.cb_lists[ev], entry, next) {
         qemu_plugin_vcpu_tb_trans_cb_t func = cb->f.vcpu_tb_trans;
 
+        qemu_plugin_set_cb_flags(cpu, QEMU_PLUGIN_CB_RW_REGS);
         func(cb->ctx->id, tb);
+        qemu_plugin_set_cb_flags(cpu, QEMU_PLUGIN_CB_NO_REGS);
     }
 }
 
@@ -498,7 +508,9 @@ qemu_plugin_vcpu_syscall(CPUState *cpu, int64_t num, uint64_t a1, uint64_t a2,
     QLIST_FOREACH_SAFE_RCU(cb, &plugin.cb_lists[ev], entry, next) {
         qemu_plugin_vcpu_syscall_cb_t func = cb->f.vcpu_syscall;
 
+        qemu_plugin_set_cb_flags(cpu, QEMU_PLUGIN_CB_RW_REGS);
         func(cb->ctx->id, cpu->cpu_index, num, a1, a2, a3, a4, a5, a6, a7, a8);
+        qemu_plugin_set_cb_flags(cpu, QEMU_PLUGIN_CB_NO_REGS);
     }
 }
 
@@ -520,7 +532,9 @@ void qemu_plugin_vcpu_syscall_ret(CPUState *cpu, int64_t num, int64_t ret)
     QLIST_FOREACH_SAFE_RCU(cb, &plugin.cb_lists[ev], entry, next) {
         qemu_plugin_vcpu_syscall_ret_cb_t func = cb->f.vcpu_syscall_ret;
 
+        qemu_plugin_set_cb_flags(cpu, QEMU_PLUGIN_CB_RW_REGS);
         func(cb->ctx->id, cpu->cpu_index, num, ret);
+        qemu_plugin_set_cb_flags(cpu, QEMU_PLUGIN_CB_NO_REGS);
     }
 }
 
@@ -528,14 +542,18 @@ void qemu_plugin_vcpu_idle_cb(CPUState *cpu)
 {
     /* idle and resume cb may be called before init, ignore in this case */
     if (cpu->cpu_index < plugin.num_vcpus) {
+        qemu_plugin_set_cb_flags(cpu, QEMU_PLUGIN_CB_RW_REGS);
         plugin_vcpu_cb__simple(cpu, QEMU_PLUGIN_EV_VCPU_IDLE);
+        qemu_plugin_set_cb_flags(cpu, QEMU_PLUGIN_CB_NO_REGS);
     }
 }
 
 void qemu_plugin_vcpu_resume_cb(CPUState *cpu)
 {
     if (cpu->cpu_index < plugin.num_vcpus) {
+        qemu_plugin_set_cb_flags(cpu, QEMU_PLUGIN_CB_RW_REGS);
         plugin_vcpu_cb__simple(cpu, QEMU_PLUGIN_EV_VCPU_RESUME);
+        qemu_plugin_set_cb_flags(cpu, QEMU_PLUGIN_CB_NO_REGS);
     }
 }
 
@@ -615,9 +633,13 @@ void qemu_plugin_vcpu_mem_cb(CPUState *cpu, uint64_t vaddr,
         switch (cb->type) {
         case PLUGIN_CB_MEM_REGULAR:
             if (rw & cb->regular.rw) {
+                qemu_plugin_set_cb_flags(cpu,
+                    tcg_call_to_qemu_plugin_cb_flags(cb->regular.info->flags));
+
                 cb->regular.f.vcpu_mem(cpu->cpu_index,
                                        make_plugin_meminfo(oi, rw),
                                        vaddr, cb->regular.userp);
+                qemu_plugin_set_cb_flags(cpu, QEMU_PLUGIN_CB_NO_REGS);
             }
             break;
         case PLUGIN_CB_INLINE_ADD_U64:
@@ -760,3 +782,14 @@ void plugin_scoreboard_free(struct qemu_plugin_scoreboard *score)
     g_array_free(score->data, TRUE);
     g_free(score);
 }
+
+enum qemu_plugin_cb_flags tcg_call_to_qemu_plugin_cb_flags(int flags)
+{
+    if (flags & TCG_CALL_NO_RWG) {
+        return QEMU_PLUGIN_CB_NO_REGS;
+    } else if (flags & TCG_CALL_NO_WG) {
+        return QEMU_PLUGIN_CB_R_REGS;
+    } else {
+        return QEMU_PLUGIN_CB_RW_REGS;
+    }
+}

semihosting/meson.build

@@ -3,15 +3,12 @@ specific_ss.add(when: 'CONFIG_SEMIHOSTING', if_true: files(
   'syscalls.c',
 ))
 
-specific_ss.add(when: ['CONFIG_SEMIHOSTING', 'CONFIG_SYSTEM_ONLY'], if_true: files(
-  'uaccess.c',
-))
-
 common_ss.add(when: 'CONFIG_SEMIHOSTING', if_false: files('stubs-all.c'))
 user_ss.add(when: 'CONFIG_SEMIHOSTING', if_true: files('user.c'))
 system_ss.add(when: 'CONFIG_SEMIHOSTING', if_true: files(
   'config.c',
   'console.c',
+  'uaccess.c',
 ), if_false: files(
   'stubs-system.c',
 ))

semihosting/uaccess.c

@@ -14,8 +14,8 @@
 #include "exec/tlb-flags.h"
 #include "semihosting/uaccess.h"
 
-void *uaccess_lock_user(CPUArchState *env, target_ulong addr,
-                        target_ulong len, bool copy)
+void *uaccess_lock_user(CPUArchState *env, vaddr addr,
+                        size_t len, bool copy)
 {
     void *p = malloc(len);
     if (p && copy) {
@@ -27,7 +27,7 @@ void *uaccess_lock_user(CPUArchState *env, target_ulong addr,
     return p;
 }
 
-ssize_t uaccess_strlen_user(CPUArchState *env, target_ulong addr)
+ssize_t uaccess_strlen_user(CPUArchState *env, vaddr addr)
 {
     int mmu_idx = cpu_mmu_index(env_cpu(env), false);
     size_t len = 0;
@@ -75,7 +75,7 @@ ssize_t uaccess_strlen_user(CPUArchState *env, target_ulong addr)
     }
 }
 
-char *uaccess_lock_user_string(CPUArchState *env, target_ulong addr)
+char *uaccess_lock_user_string(CPUArchState *env, vaddr addr)
 {
     ssize_t len = uaccess_strlen_user(env, addr);
     if (len < 0) {
@@ -85,7 +85,7 @@ char *uaccess_lock_user_string(CPUArchState *env, target_ulong addr)
 }
 
 void uaccess_unlock_user(CPUArchState *env, void *p,
-                         target_ulong addr, target_ulong len)
+                         vaddr addr, size_t len)
 {
     if (len) {
         cpu_memory_rw_debug(env_cpu(env), addr, p, len, 1);

tests/functional/meson.build

@@ -85,6 +85,7 @@ tests_aarch64_system_thorough = [
   'aarch64_aspeed_ast2700',
   'aarch64_aspeed_ast2700fc',
   'aarch64_device_passthrough',
+  'aarch64_hotplug_pci',
   'aarch64_imx8mp_evk',
   'aarch64_raspi3',
   'aarch64_raspi4',

tests/functional/test_aarch64_hotplug_pci.py

@@ -0,0 +1,72 @@
+#!/usr/bin/env python3
+#
+# The test hotplugs a PCI device and checks it on a Linux guest.
+#
+# Copyright (c) 2025 Linaro Ltd.
+#
+# Author:
+#  Gustavo Romero <gustavo.romero@linaro.org>
+#
+# SPDX-License-Identifier: GPL-2.0-or-later
+
+from qemu_test import LinuxKernelTest, Asset, exec_command_and_wait_for_pattern
+from qemu_test import BUILD_DIR
+
+class HotplugPCI(LinuxKernelTest):
+
+    ASSET_KERNEL = Asset(
+        ('https://ftp.debian.org/debian/dists/stable/main/installer-arm64/'
+         '20230607+deb12u11/images/netboot/debian-installer/arm64/linux'),
+         'd92a60392ce1e379ca198a1a820899f8f0d39a62d047c41ab79492f81541a9d9')
+
+    ASSET_INITRD = Asset(
+        ('https://ftp.debian.org/debian/dists/stable/main/installer-arm64/'
+         '20230607+deb12u11/images/netboot/debian-installer/arm64/initrd.gz'),
+         '9f817f76951f3237bca8216bee35267bfb826815687f4b2fcdd5e6c2a917790c')
+
+    def test_hotplug_pci(self):
+
+        self.set_machine('virt')
+
+        self.vm.add_args('-m', '512M',
+                         '-cpu', 'cortex-a57',
+                         '-append',
+                         'console=ttyAMA0,115200 init=/bin/sh',
+                         '-device',
+                         'pcie-root-port,bus=pcie.0,chassis=1,slot=1,id=pcie.1',
+                         '-bios',
+                         self.build_file('pc-bios', 'edk2-aarch64-code.fd'))
+
+        # BusyBox prompt
+        prompt = "~ #"
+        self.launch_kernel(self.ASSET_KERNEL.fetch(),
+                           self.ASSET_INITRD.fetch(),
+                           wait_for=prompt)
+
+        # Check for initial state: 2 network adapters, lo and enp0s1.
+        exec_command_and_wait_for_pattern(self,
+                                          'ls /sys/class/net | wc -l',
+                                          '2')
+
+        # Hotplug one network adapter to the root port, i.e. pcie.1 bus.
+        self.vm.cmd('device_add',
+                    driver='virtio-net-pci',
+                    bus='pcie.1',
+                    addr=0,
+                    id='na')
+        # Wait for the kernel to recognize the new device.
+        self.wait_for_console_pattern('virtio-pci')
+        self.wait_for_console_pattern('virtio_net')
+
+        # Check if there is a new network adapter.
+        exec_command_and_wait_for_pattern(self,
+                                          'ls /sys/class/net | wc -l',
+                                          '3')
+
+        self.vm.cmd('device_del', id='na')
+        exec_command_and_wait_for_pattern(self,
+                                          'ls /sys/class/net | wc -l',
+                                          '2')
+
+if __name__ == '__main__':
+    LinuxKernelTest.main()

tests/tcg/Makefile.target

@@ -151,7 +151,12 @@ ifeq ($(CONFIG_PLUGIN),y)
 PLUGIN_SRC=$(SRC_PATH)/tests/tcg/plugins
 PLUGIN_LIB=../plugins
 VPATH+=$(PLUGIN_LIB)
-PLUGINS=$(patsubst %.c, lib%.so, $(notdir $(wildcard $(PLUGIN_SRC)/*.c)))
+# Some plugins need to be disabled for all tests to avoid exponential explosion.
+# For example, libpatch.so only needs to run against the arch-specific patch
+# target test, so we explicitly run it in the arch-specific Makefile.
+DISABLE_PLUGINS=libpatch.so
+PLUGINS=$(filter-out $(DISABLE_PLUGINS), \
+	$(patsubst %.c, lib%.so, $(notdir $(wildcard $(PLUGIN_SRC)/*.c))))
 
 # We need to ensure expand the run-plugin-TEST-with-PLUGIN
 # pre-requistes manually here as we can't use stems to handle it. We

tests/tcg/plugins/meson.build

@@ -1,6 +1,6 @@
 t = []
 if get_option('plugins')
-  foreach i : ['bb', 'empty', 'inline', 'insn', 'mem', 'reset', 'syscall']
+  foreach i : ['bb', 'empty', 'inline', 'insn', 'mem', 'reset', 'syscall', 'patch']
     if host_os == 'windows'
       t += shared_module(i, files(i + '.c') + '../../../contrib/plugins/win32_linker.c',
                         include_directories: '../../../include/qemu',

tests/tcg/plugins/patch.c

@@ -0,0 +1,251 @@
+/*
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ *
+ * This plugin patches instructions matching a pattern to a different
+ * instruction as they execute
+ *
+ */
+
+#include "glib.h"
+#include "glibconfig.h"
+
+#include <qemu-plugin.h>
+#include <string.h>
+#include <stdio.h>
+
+QEMU_PLUGIN_EXPORT int qemu_plugin_version = QEMU_PLUGIN_VERSION;
+
+static bool use_hwaddr;
+static GByteArray *target_data;
+static GByteArray *patch_data;
+
+/**
+ * Parse a string of hexadecimal digits into a GByteArray. The string must be
+ * even length
+ */
+static GByteArray *str_to_bytes(const char *str)
+{
+    size_t len = strlen(str);
+
+    if (len == 0 || len % 2 != 0) {
+        return NULL;
+    }
+
+    GByteArray *bytes = g_byte_array_new();
+    char byte[3] = {0};
+    guint8 value = 0;
+
+    for (size_t i = 0; i < len; i += 2) {
+        byte[0] = str[i];
+        byte[1] = str[i + 1];
+        value = (guint8)g_ascii_strtoull(byte, NULL, 16);
+        g_byte_array_append(bytes, &value, 1);
+    }
+
+    return bytes;
+}
+
+static void patch_hwaddr(unsigned int vcpu_index, void *userdata)
+{
+    uintptr_t addr = (uintptr_t) userdata;
+    g_autoptr(GString) str = g_string_new(NULL);
+    g_string_printf(str, "patching: @0x%"
+                    PRIxPTR "\n",
+                    addr);
+    qemu_plugin_outs(str->str);
+
+    enum qemu_plugin_hwaddr_operation_result result =
+        qemu_plugin_write_memory_hwaddr(addr, patch_data);
+
+
+    if (result != QEMU_PLUGIN_HWADDR_OPERATION_OK) {
+        g_autoptr(GString) errmsg = g_string_new(NULL);
+        g_string_printf(errmsg, "Failed to write memory: %d\n", result);
+        qemu_plugin_outs(errmsg->str);
+        return;
+    }
+
+    GByteArray *read_data = g_byte_array_new();
+
+    result = qemu_plugin_read_memory_hwaddr(addr, read_data,
+                                            patch_data->len);
+
+    qemu_plugin_outs("Reading memory...\n");
+
+    if (result != QEMU_PLUGIN_HWADDR_OPERATION_OK) {
+        g_autoptr(GString) errmsg = g_string_new(NULL);
+        g_string_printf(errmsg, "Failed to read memory: %d\n", result);
+        qemu_plugin_outs(errmsg->str);
+        return;
+    }
+
+    if (memcmp(patch_data->data, read_data->data, patch_data->len) != 0) {
+        qemu_plugin_outs("Failed to read back written data\n");
+    }
+
+    qemu_plugin_outs("Success!\n");
+
+    return;
+}
+
+static void patch_vaddr(unsigned int vcpu_index, void *userdata)
+{
+    uintptr_t addr = (uintptr_t) userdata;
+    uint64_t hwaddr = 0;
+    if (!qemu_plugin_translate_vaddr(addr, &hwaddr)) {
+        qemu_plugin_outs("Failed to translate vaddr\n");
+        return;
+    }
+    g_autoptr(GString) str = g_string_new(NULL);
+    g_string_printf(str, "patching: @0x%"
+                    PRIxPTR " hw: @0x%" PRIx64 "\n",
+                    addr, hwaddr);
+    qemu_plugin_outs(str->str);
+
+    qemu_plugin_outs("Writing memory (vaddr)...\n");
+
+    if (!qemu_plugin_write_memory_vaddr(addr, patch_data)) {
+        qemu_plugin_outs("Failed to write memory\n");
+        return;
+    }
+
+    qemu_plugin_outs("Reading memory (vaddr)...\n");
+
+    g_autoptr(GByteArray) read_data = g_byte_array_new();
+
+    if (!qemu_plugin_read_memory_vaddr(addr, read_data, patch_data->len)) {
+        qemu_plugin_outs("Failed to read memory\n");
+        return;
+    }
+
+    if (memcmp(patch_data->data, read_data->data, patch_data->len) != 0) {
+        qemu_plugin_outs("Failed to read back written data\n");
+    }
+
+    qemu_plugin_outs("Success!\n");
+
+    return;
+}
+
+/*
+ * Callback on translation of a translation block.
+ */
+static void vcpu_tb_trans_cb(qemu_plugin_id_t id, struct qemu_plugin_tb *tb)
+{
+    g_autoptr(GByteArray) insn_data = g_byte_array_new();
+    uintptr_t addr = 0;
+
+    for (size_t i = 0; i < qemu_plugin_tb_n_insns(tb); i++) {
+        struct qemu_plugin_insn *insn = qemu_plugin_tb_get_insn(tb, i);
+        uint64_t vaddr = qemu_plugin_insn_vaddr(insn);
+
+        if (use_hwaddr) {
+            uint64_t hwaddr = 0;
+            if (!qemu_plugin_translate_vaddr(vaddr, &hwaddr)) {
+                qemu_plugin_outs("Failed to translate vaddr\n");
+                continue;
+            }
+            /*
+             * As we cannot emulate 64 bit systems on 32 bit hosts we
+             * should never see the top bits set, hence we can safely
+             * cast to uintptr_t.
+             */
+            g_assert(hwaddr <= UINTPTR_MAX);
+            addr = (uintptr_t) hwaddr;
+        } else {
+            g_assert(vaddr <= UINTPTR_MAX);
+            addr = (uintptr_t) vaddr;
+        }
+
+        g_byte_array_set_size(insn_data, qemu_plugin_insn_size(insn));
+        qemu_plugin_insn_data(insn, insn_data->data, insn_data->len);
+
+        if (insn_data->len >= target_data->len &&
+            !memcmp(insn_data->data, target_data->data,
+                    MIN(target_data->len, insn_data->len))) {
+            if (use_hwaddr) {
+                qemu_plugin_register_vcpu_tb_exec_cb(tb, patch_hwaddr,
+                                                     QEMU_PLUGIN_CB_NO_REGS,
+                                                     (void *) addr);
+            } else {
+                qemu_plugin_register_vcpu_tb_exec_cb(tb, patch_vaddr,
+                                                     QEMU_PLUGIN_CB_NO_REGS,
+                                                     (void *) addr);
+            }
+        }
+    }
+}
+
+static void usage(void)
+{
+    fprintf(stderr, "Usage: <lib>,target=<bytes>,patch=<new_bytes>"
+            "[,use_hwaddr=true|false]");
+}
+
+/*
+ * Called when the plugin is installed
+ */
+QEMU_PLUGIN_EXPORT int qemu_plugin_install(qemu_plugin_id_t id,
+                                           const qemu_info_t *info, int argc,
+                                           char **argv)
+{
+
+    use_hwaddr = true;
+    target_data = NULL;
+    patch_data = NULL;
+
+    if (argc > 4) {
+        usage();
+        return -1;
+    }
+
+    for (size_t i = 0; i < argc; i++) {
+        char *opt = argv[i];
+        g_auto(GStrv) tokens = g_strsplit(opt, "=", 2);
+        if (g_strcmp0(tokens[0], "use_hwaddr") == 0) {
+            if (!qemu_plugin_bool_parse(tokens[0], tokens[1], &use_hwaddr)) {
+                fprintf(stderr,
+                        "Failed to parse boolean argument use_hwaddr\n");
+                return -1;
+            }
+        } else if (g_strcmp0(tokens[0], "target") == 0) {
+            target_data = str_to_bytes(tokens[1]);
+            if (!target_data) {
+                fprintf(stderr,
+                         "Failed to parse target bytes.\n");
+                return -1;
+            }
+        } else if (g_strcmp0(tokens[0], "patch") == 0) {
+            patch_data = str_to_bytes(tokens[1]);
+            if (!patch_data) {
+                fprintf(stderr, "Failed to parse patch bytes.\n");
+                return -1;
+            }
+        } else {
+            fprintf(stderr, "Unknown argument: %s\n", tokens[0]);
+            usage();
+            return -1;
+        }
+    }
+
+    if (!target_data) {
+        fprintf(stderr, "target argument is required\n");
+        usage();
+        return -1;
+    }
+
+    if (!patch_data) {
+        fprintf(stderr, "patch argument is required\n");
+        usage();
+        return -1;
+    }
+
+    if (target_data->len != patch_data->len) {
+        fprintf(stderr, "Target and patch data must be the same length\n");
+        return -1;
+    }
+
+    qemu_plugin_register_vcpu_tb_trans_cb(id, vcpu_tb_trans_cb);
+
+    return 0;
+}

tests/tcg/x86_64/Makefile.softmmu-target

@@ -1,13 +1,11 @@
 #
-# x86 system tests
-#
-# This currently builds only for i386. The common C code is built
-# with standard compiler flags however so we can support both by
-# adding additional boot files for x86_64.
+# x86_64 system tests
 #
 
-I386_SYSTEM_SRC=$(SRC_PATH)/tests/tcg/i386/system
 X64_SYSTEM_SRC=$(SRC_PATH)/tests/tcg/x86_64/system
+X64_SYSTEM_TESTS=$(patsubst $(X64_SYSTEM_SRC)/%.c, %, $(wildcard $(X64_SYSTEM_SRC)/*.c))
+
+VPATH+=$(X64_SYSTEM_SRC)
 
 # These objects provide the basic boot code and helper functions for all tests
 CRT_OBJS=boot.o
@@ -18,7 +16,7 @@ LDFLAGS=-Wl,-T$(LINK_SCRIPT) -Wl,-melf_x86_64
 CFLAGS+=-nostdlib -ggdb -O0 $(MINILIB_INC)
 LDFLAGS+=-static -nostdlib $(CRT_OBJS) $(MINILIB_OBJS) -lgcc
 
-TESTS+=$(MULTIARCH_TESTS)
+TESTS+=$(MULTIARCH_TESTS) $(X64_SYSTEM_TESTS)
 EXTRA_RUNS+=$(MULTIARCH_RUNS)
 
 # building head blobs
@@ -35,3 +33,12 @@ memory: CFLAGS+=-DCHECK_UNALIGNED=1
 
 # Running
 QEMU_OPTS+=-device isa-debugcon,chardev=output -device isa-debug-exit,iobase=0xf4,iosize=0x4 -kernel
+
+ifeq ($(CONFIG_PLUGIN),y)
+run-plugin-patch-target-with-libpatch.so:		\
+	PLUGIN_ARGS=$(COMMA)target=ffc0$(COMMA)patch=9090$(COMMA)use_hwaddr=true
+run-plugin-patch-target-with-libpatch.so:		\
+	CHECK_PLUGIN_OUTPUT_COMMAND=$(X64_SYSTEM_SRC)/validate-patch.py $@.out
+run-plugin-patch-target-with-libpatch.so: patch-target libpatch.so
+EXTRA_RUNS+=run-plugin-patch-target-with-libpatch.so
+endif

tests/tcg/x86_64/system/patch-target.c

@@ -0,0 +1,22 @@
+/*
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ *
+ * This test target increments a value 100 times. The patcher converts the
+ * inc instruction to a nop, so it only increments the value once.
+ *
+ */
+#include <minilib.h>
+
+int main(void)
+{
+    ml_printf("Running test...\n");
+    unsigned int x = 0;
+    for (int i = 0; i < 100; i++) {
+        asm volatile (
+            "inc %[x]"
+            : [x] "+a" (x)
+        );
+    }
+    ml_printf("Value: %d\n", x);
+    return 0;
+}

tests/tcg/x86_64/system/validate-patch.py

@@ -0,0 +1,39 @@
+#!/usr/bin/env python3
+#
+# validate-patch.py: check the patch applies
+#
+# This program takes two inputs:
+#   - the plugin output
+#   - the binary output
+#
+# Copyright (C) 2024
+#
+# SPDX-License-Identifier: GPL-2.0-or-later
+
+import sys
+from argparse import ArgumentParser
+
+def main() -> None:
+    """
+    Process the arguments, injest the program and plugin out and
+    verify they match up and report if they do not.
+    """
+    parser = ArgumentParser(description="Validate patch")
+    parser.add_argument('test_output',
+                        help="The output from the test itself")
+    parser.add_argument('plugin_output',
+                        help="The output from plugin")
+    args = parser.parse_args()
+
+    with open(args.test_output, 'r') as f:
+        test_data = f.read()
+    with open(args.plugin_output, 'r') as f:
+        plugin_data = f.read()
+    if "Value: 1" in test_data:
+        sys.exit(0)
+    else:
+        sys.exit(1)
+
+if __name__ == "__main__":
+    main()
+