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Thu, 03 Jun 2021 06:37:34 -0700 (PDT) Received: from localhost.localdomain ([2001:b07:6468:f312:c8dd:75d4:99ab:290a]) by smtp.gmail.com with ESMTPSA id e24sm1555369ejb.52.2021.06.03.06.37.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 03 Jun 2021 06:37:33 -0700 (PDT) From: Paolo Bonzini To: qemu-devel@nongnu.org Subject: [PATCH v3 3/7] block: add max_hw_transfer to BlockLimits Date: Thu, 3 Jun 2021 15:37:18 +0200 Message-Id: <20210603133722.218465-4-pbonzini@redhat.com> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20210603133722.218465-1-pbonzini@redhat.com> References: <20210603133722.218465-1-pbonzini@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=2a00:1450:4864:20::536; envelope-from=paolo.bonzini@gmail.com; helo=mail-ed1-x536.google.com X-Spam_score_int: -14 X-Spam_score: -1.5 X-Spam_bar: - X-Spam_report: (-1.5 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_EF=-0.1, FREEMAIL_FORGED_FROMDOMAIN=0.248, FREEMAIL_FROM=0.001, HEADER_FROM_DIFFERENT_DOMAINS=0.249, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=no autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: kwolf@redhat.com, qemu-block@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" 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 --- block/block-backend.c | 12 ++++++++++++ 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, 23 insertions(+), 2 deletions(-) diff --git a/block/block-backend.c b/block/block-backend.c index 15f1ea4288..2ea1412a54 100644 --- a/block/block-backend.c +++ b/block/block-backend.c @@ -1953,6 +1953,18 @@ 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(bs->bl.max_hw_transfer, bs->bl.max_transfer); + } + return max; +} + /* 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 e3241a0dd3..f55f92d0f5 100644 --- a/block/file-posix.c +++ b/block/file-posix.c @@ -1234,7 +1234,7 @@ 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 323854d063..089b99bb0c 100644 --- a/block/io.c +++ b/block/io.c @@ -127,6 +127,7 @@ 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 82e1e2ee79..3762dce749 100644 --- a/hw/scsi/scsi-generic.c +++ b/hw/scsi/scsi-generic.c @@ -179,7 +179,7 @@ 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 057d88b1fc..f1a54db0f8 100644 --- a/include/block/block_int.h +++ b/include/block/block_int.h @@ -695,6 +695,13 @@ 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 5423e3d9c6..9ac5f7bbd3 100644 --- a/include/sysemu/block-backend.h +++ b/include/sysemu/block-backend.h @@ -208,6 +208,7 @@ 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); -- 2.31.1