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Fix iovec limits with scsi-generic

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Daniel P. Berrangé 2021-11-25 19:34:40 +00:00 committed by Richard W.M. Jones
parent f9f5de9994
commit f54452a157
2 changed files with 132 additions and 1 deletions
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124
0001-block-introduce-max_hw_iov-for-use-in-scsi-generic.patch Normal file
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@ -0,0 +1,124 @@
From cc071629539dc1f303175a7e2d4ab854c0a8b20f Mon Sep 17 00:00:00 2001
From: Paolo Bonzini <pbonzini@redhat.com>
Date: Thu, 23 Sep 2021 09:04:36 -0400
Subject: [PATCH] block: introduce max_hw_iov for use in scsi-generic
Linux limits the size of iovecs to 1024 (UIO_MAXIOV in the kernel
sources, IOV_MAX in POSIX). Because of this, on some host adapters
requests with many iovecs are rejected with -EINVAL by the
io_submit() or readv()/writev() system calls.
In fact, the same limit applies to SG_IO as well. To fix both the
EINVAL and the possible performance issues from using fewer iovecs
than allowed by Linux (some HBAs have max_segments as low as 128),
introduce a separate entry in BlockLimits to hold the max_segments
value from sysfs. This new limit is used only for SG_IO and clamped
to bs->bl.max_iov anyway, just like max_hw_transfer is clamped to
bs->bl.max_transfer.
Reported-by: Halil Pasic <pasic@linux.ibm.com>
Cc: Hanna Reitz <hreitz@redhat.com>
Cc: Kevin Wolf <kwolf@redhat.com>
Cc: qemu-block@nongnu.org
Cc: qemu-stable@nongnu.org
Fixes: 18473467d5 ("file-posix: try BLKSECTGET on block devices too, do not round to power of 2", 2021-06-25)
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20210923130436.1187591-1-pbonzini@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
block/block-backend.c | 6 ++++++
block/file-posix.c | 2 +-
block/io.c | 1 +
hw/scsi/scsi-generic.c | 2 +-
include/block/block_int.h | 7 +++++++
include/sysemu/block-backend.h | 1 +
6 files changed, 17 insertions(+), 2 deletions(-)
diff --git a/block/block-backend.c b/block/block-backend.c
index 6140d133e2..ba2b5ebb10 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -1986,6 +1986,12 @@ uint32_t blk_get_max_transfer(BlockBackend *blk)
return ROUND_DOWN(max, blk_get_request_alignment(blk));
}
+int blk_get_max_hw_iov(BlockBackend *blk)
+{
+ return MIN_NON_ZERO(blk->root->bs->bl.max_hw_iov,
+ blk->root->bs->bl.max_iov);
+}
+
int blk_get_max_iov(BlockBackend *blk)
{
return blk->root->bs->bl.max_iov;
diff --git a/block/file-posix.c b/block/file-posix.c
index c62e42743d..53be0bdc1b 100644
--- a/block/file-posix.c
+++ b/block/file-posix.c
@@ -1273,7 +1273,7 @@ static void raw_refresh_limits(BlockDriverState *bs, Error **errp)
ret = hdev_get_max_segments(s->fd, &st);
if (ret > 0) {
- bs->bl.max_iov = ret;
+ bs->bl.max_hw_iov = ret;
}
}
}
diff --git a/block/io.c b/block/io.c
index 18d345a87a..bb0a254def 100644
--- a/block/io.c
+++ b/block/io.c
@@ -136,6 +136,7 @@ static void bdrv_merge_limits(BlockLimits *dst, const BlockLimits *src)
dst->min_mem_alignment = MAX(dst->min_mem_alignment,
src->min_mem_alignment);
dst->max_iov = MIN_NON_ZERO(dst->max_iov, src->max_iov);
+ dst->max_hw_iov = MIN_NON_ZERO(dst->max_hw_iov, src->max_hw_iov);
}
typedef struct BdrvRefreshLimitsState {
diff --git a/hw/scsi/scsi-generic.c b/hw/scsi/scsi-generic.c
index 665baf900e..0306ccc7b1 100644
--- a/hw/scsi/scsi-generic.c
+++ b/hw/scsi/scsi-generic.c
@@ -180,7 +180,7 @@ static int scsi_handle_inquiry_reply(SCSIGenericReq *r, SCSIDevice *s, int len)
page = r->req.cmd.buf[2];
if (page == 0xb0) {
uint64_t max_transfer = blk_get_max_hw_transfer(s->conf.blk);
- uint32_t max_iov = blk_get_max_iov(s->conf.blk);
+ uint32_t max_iov = blk_get_max_hw_iov(s->conf.blk);
assert(max_transfer);
max_transfer = MIN_NON_ZERO(max_transfer, max_iov * qemu_real_host_page_size)
diff --git a/include/block/block_int.h b/include/block/block_int.h
index ffe86068d4..f4c75e8ba9 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -718,6 +718,13 @@ typedef struct BlockLimits {
*/
uint64_t max_hw_transfer;
+ /* Maximal number of scatter/gather elements allowed by the hardware.
+ * Applies whenever transfers to the device bypass the kernel I/O
+ * scheduler, for example with SG_IO. If larger than max_iov
+ * or if zero, blk_get_max_hw_iov will fall back to max_iov.
+ */
+ int max_hw_iov;
+
/* memory alignment, in bytes so that no bounce buffer is needed */
size_t min_mem_alignment;
diff --git a/include/sysemu/block-backend.h b/include/sysemu/block-backend.h
index 29d4fdbf63..82bae55161 100644
--- a/include/sysemu/block-backend.h
+++ b/include/sysemu/block-backend.h
@@ -211,6 +211,7 @@ uint32_t blk_get_request_alignment(BlockBackend *blk);
uint32_t blk_get_max_transfer(BlockBackend *blk);
uint64_t blk_get_max_hw_transfer(BlockBackend *blk);
int blk_get_max_iov(BlockBackend *blk);
+int blk_get_max_hw_iov(BlockBackend *blk);
void blk_set_guest_block_size(BlockBackend *blk, int align);
void *blk_try_blockalign(BlockBackend *blk, size_t size);
void *blk_blockalign(BlockBackend *blk, size_t size);
--
2.33.1

9
qemu.spec
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@ -287,7 +287,7 @@ Obsoletes: %{name}-system-unicore32-core <= %{epoch}:%{version}-%{release}
Summary: QEMU is a FAST! processor emulator
Name: qemu
Version: 6.1.0
Release: 12%{?rcrel}%{?dist}
Release: 13%{?rcrel}%{?dist}
Epoch: 2
License: GPLv2 and BSD and MIT and CC-BY
URL: http://www.qemu.org/
@ -327,6 +327,10 @@ Patch5: 0001-qxl-fix-pre-save-logic.patch
# Upstream in 6.2.
Patch6: 0001-nbd-server-Add-selinux-label-option.patch
# Fix iov length limits for scsi-generic
# https://bugzilla.redhat.com/show_bug.cgi?id=2026747
Patch7: 0001-block-introduce-max_hw_iov-for-use-in-scsi-generic.patch
BuildRequires: meson >= %{meson_version}
BuildRequires: zlib-devel
BuildRequires: glib2-devel
@ -2266,6 +2270,9 @@ useradd -r -u 107 -g qemu -G kvm -d / -s /sbin/nologin \
%changelog
* Thu Nov 25 2021 Daniel P. Berrangé <berrange@redhat.com> - 6.1.0-13
- Fix iovec limits with scsi-generic
* Wed Nov 24 2021 Richard W.M. Jones <rjones@redhat.com> - 6.1.0-12
- Add support for qemu-nbd --selinux-relabel option (RHBZ#1984938)
- Define STAP_SDT_ARG_CONSTRAINT=g on %%{arm}, workaround for: