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John Snow
bef1301acb
The intent of this patch is to further unify the creation and deletion of the sglist used for all AHCI transfers, including emulated PIO, ATAPI R/W, and native DMA R/W. By replacing ahci_start_transfer's call to ahci_populate_sglist with ahci_dma_prepare_buf, we reduce the number of direct calls where we manipulate the scatter-gather list in the AHCI code. To make this switch, the constant "0" passed as an offset in ahci_dma_prepare_buf is adjusted to use io_buffer_offset. For DMA pathways, this has no effect: io_buffer_offset is always updated to 0 at the beginning of a DMA transfer loop regardless. DMA pathways through ide_dma_cb() update the io_buffer_offset accordingly, and for circumstances where we might make several trips through this loop, this may actually correct a design flaw. For PIO pathways, the newly updated ahci_dma_prepare_buf will now prepare the sglist at the correct offset. It will also set io_buffer_size, but this is not used in the cmd_read_pio or cmd_write_pio pathways. Signed-off-by: John Snow <jsnow@redhat.com> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com> Message-id: 1414785819-26209-3-git-send-email-jsnow@redhat.com Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Read the documentation in qemu-doc.html or on http://wiki.qemu-project.org - QEMU team