From bef1301acb74d177b42890116e4eeaf26047b9e3 Mon Sep 17 00:00:00 2001 From: John Snow Date: Fri, 31 Oct 2014 16:03:38 -0400 Subject: [PATCH] ahci: unify sglist preparation 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 Reviewed-by: Paolo Bonzini Message-id: 1414785819-26209-3-git-send-email-jsnow@redhat.com Signed-off-by: Stefan Hajnoczi --- hw/ide/ahci.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/hw/ide/ahci.c b/hw/ide/ahci.c index dbd6773f8e..28aa1055dd 100644 --- a/hw/ide/ahci.c +++ b/hw/ide/ahci.c @@ -1093,7 +1093,7 @@ static void ahci_start_transfer(IDEDMA *dma) goto out; } - if (!ahci_populate_sglist(ad, &s->sg, s->io_buffer_offset)) { + if (ahci_dma_prepare_buf(dma, is_write)) { has_sglist = 1; } @@ -1145,7 +1145,7 @@ static int ahci_dma_prepare_buf(IDEDMA *dma, int is_write) AHCIDevice *ad = DO_UPCAST(AHCIDevice, dma, dma); IDEState *s = &ad->port.ifs[0]; - ahci_populate_sglist(ad, &s->sg, 0); + ahci_populate_sglist(ad, &s->sg, s->io_buffer_offset); s->io_buffer_size = s->sg.size; DPRINTF(ad->port_no, "len=%#x\n", s->io_buffer_size); -- 2.11.4.GIT