Yes, the question is whether it still exists... Paolo El jue., 23 sept. 2021 16:48, Christian Borntraeger 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 > > Cc: Hanna Reitz > > Cc: Kevin Wolf > > Cc: 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 > > --- > > 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); > > > >