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qemu.30222
block-add-max_hw_transfer-to-BlockLimits.patch
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File block-add-max_hw_transfer-to-BlockLimits.patch of Package qemu.30222
From: Lin Ma <lma@suse.com> Date: Mon, 13 Sep 2021 18:33:11 +0800 Subject: block: add max_hw_transfer to BlockLimits Git-commit: 24b36e9813ec15da7db62e3b3621730710c5f020 References: bsc#1190425 For block host devices, I/O can happen through either the kernel file descriptor I/O system calls (preadv/pwritev, io_submit, io_uring) or the SCSI passthrough ioctl SG_IO. In the latter case, the size of each transfer can be limited by the HBA, while for file descriptor I/O the kernel is able to split and merge I/O in smaller pieces as needed. Applying the HBA limits to file descriptor I/O results in more system calls and suboptimal performance, so this patch splits the max_transfer limit in two: max_transfer remains valid and is used in general, while max_hw_transfer is limited to the maximum hardware size. max_hw_transfer can then be included by the scsi-generic driver in the block limits page, to ensure that the stricter hardware limit is used. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Lin Ma <lma@suse.com> --- block/block-backend.c | 13 +++++++++++++ block/file-posix.c | 2 +- block/io.c | 2 ++ hw/scsi/scsi-generic.c | 2 +- include/block/block_int.h | 7 +++++++ include/sysemu/block-backend.h | 1 + 6 files changed, 25 insertions(+), 2 deletions(-) diff --git a/block/block-backend.c b/block/block-backend.c index dfb0fd41e52372c2373ba27d62b1..6fafe601a27f13d77cbea7c78b42 100644 --- a/block/block-backend.c +++ b/block/block-backend.c @@ -1939,6 +1939,19 @@ uint32_t blk_get_request_alignment(BlockBackend *blk) return bs ? bs->bl.request_alignment : BDRV_SECTOR_SIZE; } +/* Returns the maximum hardware transfer length, in bytes; guaranteed nonzero */ +uint64_t blk_get_max_hw_transfer(BlockBackend *blk) +{ + BlockDriverState *bs = blk_bs(blk); + uint64_t max = INT_MAX; + + if (bs) { + max = MIN_NON_ZERO(max, bs->bl.max_hw_transfer); + max = MIN_NON_ZERO(max, bs->bl.max_transfer); + } + return ROUND_DOWN(max, blk_get_request_alignment(blk)); +} + /* Returns the maximum transfer length, in bytes; guaranteed nonzero */ uint32_t blk_get_max_transfer(BlockBackend *blk) { diff --git a/block/file-posix.c b/block/file-posix.c index 72a259923b4db9b133a37572b79a..649a5408195c16c38dc09d9048da 100644 --- a/block/file-posix.c +++ b/block/file-posix.c @@ -1245,7 +1245,7 @@ static void raw_refresh_limits(BlockDriverState *bs, Error **errp) int ret = sg_get_max_transfer_length(s->fd); if (ret > 0 && ret <= BDRV_REQUEST_MAX_BYTES) { - bs->bl.max_transfer = pow2floor(ret); + bs->bl.max_hw_transfer = pow2floor(ret); } ret = sg_get_max_segments(s->fd); diff --git a/block/io.c b/block/io.c index a9f56a9ab1c56a3ca83833bfb0fa..28134b85c8a19ab10a4191e3b725 100644 --- a/block/io.c +++ b/block/io.c @@ -126,6 +126,8 @@ static void bdrv_merge_limits(BlockLimits *dst, const BlockLimits *src) { dst->opt_transfer = MAX(dst->opt_transfer, src->opt_transfer); dst->max_transfer = MIN_NON_ZERO(dst->max_transfer, src->max_transfer); + dst->max_hw_transfer = MIN_NON_ZERO(dst->max_hw_transfer, + src->max_hw_transfer); dst->opt_mem_alignment = MAX(dst->opt_mem_alignment, src->opt_mem_alignment); dst->min_mem_alignment = MAX(dst->min_mem_alignment, diff --git a/hw/scsi/scsi-generic.c b/hw/scsi/scsi-generic.c index 0cc4f9dc22edd8881da5ccddcb90..ca7f70bb1c60ab6eb7a3b64983b7 100644 --- a/hw/scsi/scsi-generic.c +++ b/hw/scsi/scsi-generic.c @@ -166,7 +166,7 @@ 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); + uint64_t max_transfer = blk_get_max_hw_transfer(s->conf.blk); uint32_t max_iov = blk_get_max_iov(s->conf.blk); assert(max_transfer); diff --git a/include/block/block_int.h b/include/block/block_int.h index 95d9333be14f220f96754c3cdd73..017f2a105ad7b74194ee1aab9395 100644 --- a/include/block/block_int.h +++ b/include/block/block_int.h @@ -678,6 +678,13 @@ typedef struct BlockLimits { * clamped down. */ uint32_t max_transfer; + /* Maximal hardware transfer length in bytes. Applies whenever + * transfers to the device bypass the kernel I/O scheduler, for + * example with SG_IO. If larger than max_transfer or if zero, + * blk_get_max_hw_transfer will fall back to max_transfer. + */ + uint64_t max_hw_transfer; + /* 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 880e9032930b0207e2e3e6fe1bd7..07ef7844a2da6aa05f816a1aa10c 100644 --- a/include/sysemu/block-backend.h +++ b/include/sysemu/block-backend.h @@ -204,6 +204,7 @@ void blk_eject(BlockBackend *blk, bool eject_flag); int blk_get_flags(BlockBackend *blk); 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); void blk_set_guest_block_size(BlockBackend *blk, int align); void *blk_try_blockalign(BlockBackend *blk, size_t size);
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