From d2634e18286a5772f04cc724e64f8b16a2124587 Mon Sep 17 00:00:00 2001 From: Kevin Wolf Date: Fri, 24 Oct 2025 14:30:38 +0200 Subject: [PATCH] block: Expose block limits for images in QMP This information can be useful both for debugging and for management tools trying to configure guest devices with the optimal limits (possibly across multiple hosts). There is no reason not to make it available, so just add it to BlockNodeInfo. Signed-off-by: Kevin Wolf Reviewed-by: Eric Blake Reviewed-by: Hanna Czenczek Message-ID: <20251024123041.51254-3-kwolf@redhat.com> Signed-off-by: Kevin Wolf --- block/qapi.c | 34 ++++++++++++++-- qapi/block-core.json | 66 ++++++++++++++++++++++++++++++++ tests/qemu-iotests/184 | 5 ++- tests/qemu-iotests/184.out | 8 ---- tests/qemu-iotests/common.filter | 3 +- 5 files changed, 102 insertions(+), 14 deletions(-) diff --git a/block/qapi.c b/block/qapi.c index 12fbf8d1b7f..54521d0a68b 100644 --- a/block/qapi.c +++ b/block/qapi.c @@ -235,7 +235,8 @@ int bdrv_query_snapshot_info_list(BlockDriverState *bs, * in @info, setting @errp on error. */ static void GRAPH_RDLOCK -bdrv_do_query_node_info(BlockDriverState *bs, BlockNodeInfo *info, Error **errp) +bdrv_do_query_node_info(BlockDriverState *bs, BlockNodeInfo *info, bool limits, + Error **errp) { int64_t size; const char *backing_filename; @@ -269,6 +270,33 @@ bdrv_do_query_node_info(BlockDriverState *bs, BlockNodeInfo *info, Error **errp) info->dirty_flag = bdi.is_dirty; info->has_dirty_flag = true; } + + if (limits) { + info->limits = g_new(BlockLimitsInfo, 1); + *info->limits = (BlockLimitsInfo) { + .request_alignment = bs->bl.request_alignment, + .has_max_discard = bs->bl.max_pdiscard != 0, + .max_discard = bs->bl.max_pdiscard, + .has_discard_alignment = bs->bl.pdiscard_alignment != 0, + .discard_alignment = bs->bl.pdiscard_alignment, + .has_max_write_zeroes = bs->bl.max_pwrite_zeroes != 0, + .max_write_zeroes = bs->bl.max_pwrite_zeroes, + .has_write_zeroes_alignment = bs->bl.pwrite_zeroes_alignment != 0, + .write_zeroes_alignment = bs->bl.pwrite_zeroes_alignment, + .has_opt_transfer = bs->bl.opt_transfer != 0, + .opt_transfer = bs->bl.opt_transfer, + .has_max_transfer = bs->bl.max_transfer != 0, + .max_transfer = bs->bl.max_transfer, + .has_max_hw_transfer = bs->bl.max_hw_transfer != 0, + .max_hw_transfer = bs->bl.max_hw_transfer, + .max_iov = bs->bl.max_iov, + .has_max_hw_iov = bs->bl.max_hw_iov != 0, + .max_hw_iov = bs->bl.max_hw_iov, + .min_mem_alignment = bs->bl.min_mem_alignment, + .opt_mem_alignment = bs->bl.opt_mem_alignment, + }; + } + info->format_specific = bdrv_get_specific_info(bs, &err); if (err) { error_propagate(errp, err); @@ -343,7 +371,7 @@ void bdrv_query_image_info(BlockDriverState *bs, ImageInfo *info; info = g_new0(ImageInfo, 1); - bdrv_do_query_node_info(bs, qapi_ImageInfo_base(info), errp); + bdrv_do_query_node_info(bs, qapi_ImageInfo_base(info), true, errp); if (*errp) { goto fail; } @@ -397,7 +425,7 @@ void bdrv_query_block_graph_info(BlockDriverState *bs, BdrvChild *c; info = g_new0(BlockGraphInfo, 1); - bdrv_do_query_node_info(bs, qapi_BlockGraphInfo_base(info), errp); + bdrv_do_query_node_info(bs, qapi_BlockGraphInfo_base(info), false, errp); if (*errp) { goto fail; } diff --git a/qapi/block-core.json b/qapi/block-core.json index dc6eb4ae23d..2c037183f00 100644 --- a/qapi/block-core.json +++ b/qapi/block-core.json @@ -275,6 +275,69 @@ 'file': 'ImageInfoSpecificFileWrapper' } } +## +# @BlockLimitsInfo: +# +# @request-alignment: Alignment requirement, in bytes, for +# offset/length of I/O requests. +# +# @max-discard: Maximum number of bytes that can be discarded at once. +# If not present, there is no specific maximum. +# +# @discard-alignment: Optimal alignment for discard requests in bytes. +# Note that this doesn't have to be a power of two. If not +# present, discards don't have a alignment requirement different +# from @request-alignment. +# +# @max-write-zeroes: Maximum number of bytes that can be zeroed out at +# once. If not present, there is no specific maximum. +# +# @write-zeroes-alignment: Optimal alignment for write zeroes requests +# in bytes. Note that this doesn't have to be a power of two. If +# not present, write_zeroes doesn't have a alignment requirement +# different from @request-alignment. +# +# @opt-transfer: Optimal transfer length in bytes. If not present, +# there is no preferred size. +# +# @max-transfer: Maximal transfer length in bytes. If not present, +# there is no specific maximum. +# +# @max-hw-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 not present, there is no +# specific maximum. +# +# @max-iov: Maximum number of scatter/gather elements +# +# @max-hw-iov: Maximum 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 not +# present, the hardware limits is unknown and @max-iov is always +# used. +# +# @min-mem-alignment: Minimal required memory alignment in bytes for +# zero-copy I/O to succeed. For unaligned requests, a bounce +# buffer will be used. +# +# @opt-mem-alignment: Optimal memory alignment in bytes. This is the +# alignment used for any buffer allocations QEMU performs +# internally. +## +{ 'struct': 'BlockLimitsInfo', + 'data': { 'request-alignment': 'uint32', + '*max-discard': 'uint64', + '*discard-alignment': 'uint32', + '*max-write-zeroes': 'uint64', + '*write-zeroes-alignment': 'uint32', + '*opt-transfer': 'uint32', + '*max-transfer': 'uint32', + '*max-hw-transfer': 'uint32', + 'max-iov': 'int', + '*max-hw-iov': 'int', + 'min-mem-alignment': 'size', + 'opt-mem-alignment': 'size' } } + ## # @BlockNodeInfo: # @@ -304,6 +367,8 @@ # # @snapshots: list of VM snapshots # +# @limits: block limits that are used for I/O on the node (Since 10.2) +# # @format-specific: structure supplying additional format-specific # information (since 1.7) # @@ -315,6 +380,7 @@ '*cluster-size': 'int', '*encrypted': 'bool', '*compressed': 'bool', '*backing-filename': 'str', '*full-backing-filename': 'str', '*backing-filename-format': 'str', '*snapshots': ['SnapshotInfo'], + '*limits': 'BlockLimitsInfo', '*format-specific': 'ImageInfoSpecific' } } ## diff --git a/tests/qemu-iotests/184 b/tests/qemu-iotests/184 index e4cbcd86345..6d0afe9d388 100755 --- a/tests/qemu-iotests/184 +++ b/tests/qemu-iotests/184 @@ -45,8 +45,9 @@ do_run_qemu() run_qemu() { - do_run_qemu "$@" 2>&1 | _filter_testdir | _filter_qemu | _filter_qmp\ - | _filter_qemu_io | _filter_generated_node_ids + do_run_qemu "$@" 2>&1 | _filter_testdir | _filter_qemu | _filter_qmp \ + | _filter_qemu_io | _filter_generated_node_ids \ + | _filter_img_info } test_throttle=$($QEMU_IMG --help|grep throttle) diff --git a/tests/qemu-iotests/184.out b/tests/qemu-iotests/184.out index ef99bb2e9ab..52692b6b3b9 100644 --- a/tests/qemu-iotests/184.out +++ b/tests/qemu-iotests/184.out @@ -41,12 +41,6 @@ Testing: }, "iops_wr": 0, "ro": false, - "children": [ - { - "node-name": "disk0", - "child": "file" - } - ], "node-name": "throttle0", "backing_file_depth": 1, "drv": "throttle", @@ -75,8 +69,6 @@ Testing: }, "iops_wr": 0, "ro": false, - "children": [ - ], "node-name": "disk0", "backing_file_depth": 0, "drv": "null-co", diff --git a/tests/qemu-iotests/common.filter b/tests/qemu-iotests/common.filter index 511a55b1e88..26e6b45b041 100644 --- a/tests/qemu-iotests/common.filter +++ b/tests/qemu-iotests/common.filter @@ -229,6 +229,7 @@ _filter_img_info() discard=0 regex_json_spec_start='^ *"format-specific": \{' regex_json_child_start='^ *"children": \[' + regex_json_limit_start='^ *"limits": \{' gsed -e "s#$REMOTE_TEST_DIR#TEST_DIR#g" \ -e "s#$IMGPROTO:$TEST_DIR#TEST_DIR#g" \ -e "s#$TEST_DIR#TEST_DIR#g" \ @@ -261,7 +262,7 @@ _filter_img_info() discard=1 elif [[ $line =~ "Child node '/" ]]; then discard=1 - elif [[ $line =~ $regex_json_spec_start ]]; then + elif [[ $line =~ $regex_json_spec_start || $line =~ $regex_json_limit_start ]]; then discard=2 regex_json_end="^${line%%[^ ]*}\\},? *$" elif [[ $line =~ $regex_json_child_start ]]; then -- 2.47.3