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Re: [PATCH] block: introduce max_hw_iov for use in scsi-generic
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From: |
Michael Roth |
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Subject: |
Re: [PATCH] block: introduce max_hw_iov for use in scsi-generic |
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Date: |
Fri, 24 Sep 2021 10:03:19 -0500 |
On Fri, Sep 24, 2021 at 08:50:05AM +0200, Christian Borntraeger wrote:
> Peter, Michael,
>
> do we still do stable releases for QEMU or has this stopped?
Hi Christian,
Yes, it's just been a perfect storm of job moves / bad timing / much-needed
testing rework. I plan to restart the stable releases starting with 6.0.1 and
6.1.1 shortly after. I'll get the release schedules posted on the release wiki
week.
Sorry for the delays on this.
-Mike
>
> Am 24.09.21 um 07:27 schrieb Paolo Bonzini:
> > Yes, the question is whether it still exists... Paolo El jue., 23 sept.
> > 2021 16:48, Christian Borntraeger <borntraeger@de.ibm.com> escribió: Am
> > 23.09.21 um 15:04 schrieb Paolo Bonzini: > Linux limits the size of iovecs
> > to 1024 (UIO_MAXIOV ZjQcmQRYFpfptBannerStart
> > This Message Is From an External Sender
> > This message came from outside your organization.
> > ZjQcmQRYFpfptBannerEnd
> > Yes, the question is whether it still exists...
> >
> > Paolo
> >
> > El jue., 23 sept. 2021 16:48, Christian Borntraeger <borntraeger@de.ibm.com
> > <mailto:borntraeger@de.ibm.com>> escribió:
> >
> >
> >
> > Am 23.09.21 um 15:04 schrieb Paolo Bonzini:
> > > 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
> > <mailto:pasic@linux.ibm.com>>
> > > Cc: Hanna Reitz <hreitz@redhat.com <mailto:hreitz@redhat.com>>
> > > Cc: Kevin Wolf <kwolf@redhat.com <mailto:kwolf@redhat.com>>
> > > Cc: qemu-block@nongnu.org <mailto:qemu-block@nongnu.org>
> > > Fixes: 18473467d5 ("file-posix: try BLKSECTGET on block devices too,
> > do not round to power of 2", 2021-06-25)
> >
> > This sneaked in shortly before the 6.1 release (between rc0 and rc1 I
> > think).
> > Shouldnt that go to stable in cass this still exist?
> >
> >
> > > Signed-off-by: Paolo Bonzini <pbonzini@redhat.com
> > <mailto:pbonzini@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 cb9bffe047..1567edb3d5 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 a19942718b..f38e7f81d8 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 f1a54db0f8..c31cbd034a 100644
> > > --- a/include/block/block_int.h
> > > +++ b/include/block/block_int.h
> > > @@ -702,6 +702,13 @@ 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);
> > >
> >