From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:51900) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1b4vf6-0005Wi-Eo for qemu-devel@nongnu.org; Mon, 23 May 2016 15:37:13 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1b4vf4-0007Fo-AJ for qemu-devel@nongnu.org; Mon, 23 May 2016 15:37:11 -0400 References: <1464008051-6429-1-git-send-email-pbonzini@redhat.com> From: Mark Cave-Ayland Message-ID: <57435BB8.3000600@ilande.co.uk> Date: Mon, 23 May 2016 20:36:24 +0100 MIME-Version: 1.0 In-Reply-To: <1464008051-6429-1-git-send-email-pbonzini@redhat.com> Content-Type: multipart/mixed; boundary="------------080702040008060607070804" Subject: Re: [Qemu-devel] [PATCH v2 0/7] dma-helpers, scsi-block: use SG_IO for all I/O on scsi-block List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Paolo Bonzini , qemu-devel@nongnu.org Cc: qemu-block@nongnu.org This is a multi-part message in MIME format. --------------080702040008060607070804 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit On 23/05/16 13:54, Paolo Bonzini wrote: > scsi-block uses the block layer for reads and writes in order to avoid > allocating bounce buffers as big as the transferred data. We know how > to split a large transfer to multiple reads and writes, and thus we can > use scsi-disk.c's existing code to do I/O in multiple chunks (for non-s/g > SCSI hosts) or through the DMA helpers (for s/g SCSI hosts). > > Unfortunately, this has the side effect of eating the SCSI status except > in the very few cases where we can convert an errno code back to a SCSI > status. It puts a big wrench in persistent reservations support in the > guest, for example. > > Luckily, splitting a large transfer into multiple SBC commands is just as > easy, and this is what the last patch does. It takes the original CDB, > patches in a modified starting sector and sector count, and executes the > SCSI command through blk_aio_ioctl. It is also easy to pass a QEMUIOVector > to SG_IO, so that s/g SCSI hosts keep the performance. > > This rebases the patches on top of Eric's changes for byte-based > BlockBackend access and fixes a few bugs I knew about in the RFC. > > Patches 1, 5 and 6 are new. > > Paolo > > Paolo Bonzini (7): > dma-helpers: change interface to byte-based > dma-helpers: change BlockBackend to opaque value in DMAIOFunc > scsi-disk: introduce a common base class > scsi-disk: introduce dma_readv and dma_writev > scsi-disk: add need_fua_emulation to SCSIDiskClass > scsi-disk: introduce scsi_disk_req_check_error > scsi-block: always use SG_IO > > dma-helpers.c | 54 +++++-- > hw/block/nvme.c | 6 +- > hw/ide/ahci.c | 6 +- > hw/ide/core.c | 20 ++- > hw/ide/internal.h | 6 +- > hw/ide/macio.c | 2 +- > hw/scsi/scsi-disk.c | 409 +++++++++++++++++++++++++++++++++++++-------------- > include/sysemu/dma.h | 20 +-- > trace-events | 2 +- > 9 files changed, 371 insertions(+), 154 deletions(-) Hi Paolo, I thought I'd give this patchset a spin with a view to seeing whether I could switch the macio device back to the now byte-based dma-helpers, but came up with a couple of compile errors. Attached is the minor diff I applied in order to get a successful compile (apologies for not being inline, however I couldn't get my mail client to stop wrapping incorrectly). ATB, Mark. --------------080702040008060607070804 Content-Type: text/x-diff; name="dma-helpers-compile-fix.patch" Content-Transfer-Encoding: 7bit Content-Disposition: attachment; filename="dma-helpers-compile-fix.patch" diff --git a/dma-helpers.c b/dma-helpers.c index 92c5d55..b521d84 100644 --- a/dma-helpers.c +++ b/dma-helpers.c @@ -192,7 +192,7 @@ static const AIOCBInfo dma_aiocb_info = { }; BlockAIOCB *dma_blk_io(AioContext *ctx, - QEMUSGList *sg, uint64_t opaque, + QEMUSGList *sg, uint64_t offset, DMAIOFunc *io_func, void *io_func_opaque, BlockCompletionFunc *cb, void *opaque, DMADirection dir) diff --git a/hw/scsi/scsi-disk.c b/hw/scsi/scsi-disk.c index 02faa3a..f7a23fc 100644 --- a/hw/scsi/scsi-disk.c +++ b/hw/scsi/scsi-disk.c @@ -540,7 +540,6 @@ static void scsi_write_data(SCSIRequest *req) if (r->req.sg) { dma_acct_start(s->qdev.conf.blk, &r->acct, r->req.sg, BLOCK_ACCT_WRITE); r->req.resid -= r->req.sg->size; - scsi_dma_complete, r); r->req.aiocb = dma_blk_io(blk_get_aio_context(s->qdev.conf.blk), r->req.sg, r->sector << BDRV_SECTOR_BITS, sdc->dma_writev, r, scsi_dma_complete, r, --------------080702040008060607070804--