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