From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [140.186.70.92] (port=42875 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1PNe1o-0006LE-7m for qemu-devel@nongnu.org; Tue, 30 Nov 2010 23:11:09 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1PNUSY-00067Q-It for qemu-devel@nongnu.org; Tue, 30 Nov 2010 12:57:48 -0500 Received: from mx1.redhat.com ([209.132.183.28]:2445) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1PNUSY-00061Z-9a for qemu-devel@nongnu.org; Tue, 30 Nov 2010 12:57:46 -0500 From: Kevin Wolf Date: Tue, 30 Nov 2010 18:58:19 +0100 Message-Id: <1291139900-20329-16-git-send-email-kwolf@redhat.com> In-Reply-To: <1291139900-20329-1-git-send-email-kwolf@redhat.com> References: <1291139900-20329-1-git-send-email-kwolf@redhat.com> Subject: [Qemu-devel] [PATCH 15/16] ide: Ignore double DMA transfer starts/stops List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: anthony@codemonkey.ws Cc: kwolf@redhat.com, qemu-devel@nongnu.org You can only start a DMA transfer if it's not running yet, and you can only cancel it if it's running. Signed-off-by: Kevin Wolf Reviewed-by: Stefan Hajnoczi --- hw/ide/pci.c | 60 ++++++++++++++++++++++++++++++--------------------------- 1 files changed, 32 insertions(+), 28 deletions(-) diff --git a/hw/ide/pci.c b/hw/ide/pci.c index 3722b77..404f045 100644 --- a/hw/ide/pci.c +++ b/hw/ide/pci.c @@ -39,38 +39,42 @@ void bmdma_cmd_writeb(void *opaque, uint32_t addr, uint32_t val) #ifdef DEBUG_IDE printf("%s: 0x%08x\n", __func__, val); #endif - if (!(val & BM_CMD_START)) { - /* - * We can't cancel Scatter Gather DMA in the middle of the - * operation or a partial (not full) DMA transfer would reach - * the storage so we wait for completion instead (we beahve - * like if the DMA was completed by the time the guest trying - * to cancel dma with bmdma_cmd_writeb with BM_CMD_START not - * set). - * - * In the future we'll be able to safely cancel the I/O if the - * whole DMA operation will be submitted to disk with a single - * aio operation with preadv/pwritev. - */ - if (bm->aiocb) { - qemu_aio_flush(); + + /* Ignore writes to SSBM if it keeps the old value */ + if ((val & BM_CMD_START) != (bm->cmd & BM_CMD_START)) { + if (!(val & BM_CMD_START)) { + /* + * We can't cancel Scatter Gather DMA in the middle of the + * operation or a partial (not full) DMA transfer would reach + * the storage so we wait for completion instead (we beahve + * like if the DMA was completed by the time the guest trying + * to cancel dma with bmdma_cmd_writeb with BM_CMD_START not + * set). + * + * In the future we'll be able to safely cancel the I/O if the + * whole DMA operation will be submitted to disk with a single + * aio operation with preadv/pwritev. + */ + if (bm->aiocb) { + qemu_aio_flush(); #ifdef DEBUG_IDE - if (bm->aiocb) - printf("ide_dma_cancel: aiocb still pending"); - if (bm->status & BM_STATUS_DMAING) - printf("ide_dma_cancel: BM_STATUS_DMAING still pending"); + if (bm->aiocb) + printf("ide_dma_cancel: aiocb still pending"); + if (bm->status & BM_STATUS_DMAING) + printf("ide_dma_cancel: BM_STATUS_DMAING still pending"); #endif + } + } else { + if (!(bm->status & BM_STATUS_DMAING)) { + bm->status |= BM_STATUS_DMAING; + /* start dma transfer if possible */ + if (bm->dma_cb) + bm->dma_cb(bm, 0); + } } - bm->cmd = val & 0x09; - } else { - if (!(bm->status & BM_STATUS_DMAING)) { - bm->status |= BM_STATUS_DMAING; - /* start dma transfer if possible */ - if (bm->dma_cb) - bm->dma_cb(bm, 0); - } - bm->cmd = val & 0x09; } + + bm->cmd = val & 0x09; } static void bmdma_addr_read(IORange *ioport, uint64_t addr, -- 1.7.2.3