From 05038edf628c6bca7cef061b7b1fac2b0b2163af Mon Sep 17 00:00:00 2001 From: Paolo Bonzini Date: Fri, 16 Jul 2021 16:51:30 -0400 Subject: [PATCH 14/43] scsi-generic: pass max_segments via max_iov field in BlockLimits RH-Author: Miroslav Rezanina RH-Bugzilla: 1957194 I/O to a disk via read/write is not limited by the number of segments allowed by the host adapter; the kernel can split requests if needed, and the limit imposed by the host adapter can be very low (256k or so) to avoid that SG_IO returns EINVAL if memory is heavily fragmented. Since this value is only interesting for SG_IO-based I/O, do not include it in the max_transfer and only take it into account when patching the block limits VPD page in the scsi-generic device. Signed-off-by: Paolo Bonzini Reviewed-by: Max Reitz (cherry picked from commit 01ef8185b809af9d287e1a03a3f9d8ea8231118a) Signed-off-by: Danilo C. L. de Paula Signed-off-by: Miroslav Rezanina --- block/file-posix.c | 3 +-- hw/scsi/scsi-generic.c | 6 ++++-- 2 files changed, 5 insertions(+), 4 deletions(-) diff --git a/block/file-posix.c b/block/file-posix.c index 74d4903dc1..1a6c799e19 100644 --- a/block/file-posix.c +++ b/block/file-posix.c @@ -1263,8 +1263,7 @@ static void raw_refresh_limits(BlockDriverState *bs, Error **errp) ret = sg_get_max_segments(s->fd); if (ret > 0) { - bs->bl.max_transfer = MIN(bs->bl.max_transfer, - ret * qemu_real_host_page_size); + bs->bl.max_iov = ret; } } diff --git a/hw/scsi/scsi-generic.c b/hw/scsi/scsi-generic.c index 98c30c5d5c..82e1e2ee79 100644 --- a/hw/scsi/scsi-generic.c +++ b/hw/scsi/scsi-generic.c @@ -179,10 +179,12 @@ static void scsi_handle_inquiry_reply(SCSIGenericReq *r, SCSIDevice *s) (r->req.cmd.buf[1] & 0x01)) { page = r->req.cmd.buf[2]; if (page == 0xb0) { - uint32_t max_transfer = - blk_get_max_transfer(s->conf.blk) / s->blocksize; + uint32_t max_transfer = blk_get_max_transfer(s->conf.blk); + uint32_t max_iov = blk_get_max_iov(s->conf.blk); assert(max_transfer); + max_transfer = MIN_NON_ZERO(max_transfer, max_iov * qemu_real_host_page_size) + / s->blocksize; stl_be_p(&r->buf[8], max_transfer); /* Also take care of the opt xfer len. */ stl_be_p(&r->buf[12], -- 2.27.0