SaveState: Refuse savestates and rewind in a session booted into the XMB

Inserting and ejecting a disc there adds and removes the umd0:/umd1:/
umd:/disc0: mounts, and MetaFileSystem's state pairs sections with mounts
by position without recording which disc was in. A state could then fail
to load, or load one disc's open files onto another. The pause screen
already hid its save buttons for vshmain.prx; the save hotkeys, rewind,
the ImDebugger and the WebSocket debugger all went around that. The check
is now in SaveState itself, and rewind snapshots aren't taken. Verify
still runs, since it reads back with the mounts as they are.

A proper fix records the mounted image in sceUmd's state and remounts it
on load.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

Core/SaveState.cpp

@@ -31,6 +31,7 @@
 #include "Common/Thread/ThreadUtil.h"
 #include "Common/Data/Text/Parsers.h"
 #include "Common/System/System.h"
+#include "Common/System/OSD.h"
 
 #include "Common/File/FileUtil.h"
 #include "Common/File/DirListing.h"
@@ -424,6 +425,23 @@ int g_screenshotFailures;
 		}
 	}
 
+	// A session booted into the XMB inserts and ejects discs, which changes the mounts, and keeps
+	// doing so for a game launched from it. MetaFileSystem's state pairs its sections with mounts by
+	// position and doesn't record which disc was in, so a state from such a session could fail to
+	// load, or load one disc's file state onto another.
+	static bool IsVSHSession() {
+		return PSP_CoreParameter().fileToStart.GetFilename() == "vshmain.prx";
+	}
+
+	static bool WarnUserIfVSHSession() {
+		if (!IsVSHSession()) {
+			return false;
+		}
+		auto pa = GetI18NCategory(I18NCat::PAUSE);
+		g_OSD.Show(OSDType::MESSAGE_INFO, pa->T("Save states are not available in the XMB"), 3.0f, "savevsh");
+		return true;
+	}
+
 	bool Enqueue(const SaveState::Operation &op) {
 		// These two both refuse the operation, and both say so - dropping it silently just
 		// looks like the hotkey didn't work. Callers that ask the same questions themselves
@@ -438,6 +456,11 @@ int g_screenshotFailures;
 			CallbackRefused(op.callback);
 			return false;
 		}
+		// Verify saves and loads back in place, with the mounts as they are.
+		if (op.type != OperationType::Verify && WarnUserIfVSHSession()) {
+			CallbackRefused(op.callback);
+			return false;
+		}
 
 		std::lock_guard<std::mutex> guard(mutex);
 		g_pendingOperations.push_back(op);
@@ -660,7 +683,7 @@ int g_screenshotFailures;
 
 	void LoadSlot(std::string_view gamePrefix, int slot, Callback callback) {
 		// Enqueue() would refuse too, but only after the load undo backup below has replaced the old one.
-		if (NetworkWarnUserIfOnlineAndCantSavestate() || Achievements::WarnUserIfHardcoreModeActive(false)) {
+		if (NetworkWarnUserIfOnlineAndCantSavestate() || Achievements::WarnUserIfHardcoreModeActive(false) || WarnUserIfVSHSession()) {
 			CallbackRefused(callback);
 			return;
 		}
@@ -716,7 +739,7 @@ int g_screenshotFailures;
 
 	void SaveSlot(std::string_view gamePrefix, int slot, Callback callback) {
 		// Enqueue() would refuse too, but only after the screenshots below have been rotated.
-		if (NetworkWarnUserIfOnlineAndCantSavestate() || Achievements::WarnUserIfHardcoreModeActive(true)) {
+		if (NetworkWarnUserIfOnlineAndCantSavestate() || Achievements::WarnUserIfHardcoreModeActive(true) || WarnUserIfVSHSession()) {
 			CallbackRefused(callback);
 			return;
 		}
@@ -1481,7 +1504,7 @@ int g_screenshotFailures;
 
 	// NOTE: This can cause ending of the current renderpass, due to the readback needed for the screenshot.
 	void Process(bool takeRewindSnapshots) {
-		if (takeRewindSnapshots) {
+		if (takeRewindSnapshots && !IsVSHSession()) {
 			rewindStates.Process();
 		}
 		RunCompletions(true);