* [RFC v4 00/11] blkio: add libblkio BlockDriver
@ 2022-08-22 22:23 Stefan Hajnoczi
2022-08-22 22:23 ` [RFC v4 01/11] blkio: add libblkio block driver Stefan Hajnoczi
` (11 more replies)
0 siblings, 12 replies; 23+ messages in thread
From: Stefan Hajnoczi @ 2022-08-22 22:23 UTC (permalink / raw)
To: qemu-devel
Cc: Paolo Bonzini, Denis V. Lunev, Peter Xu, Yanan Wang,
Marcel Apfelbaum, Richard W.M. Jones, qemu-block, John Snow,
integration, Vladimir Sementsov-Ogievskiy,
Vladimir Sementsov-Ogievskiy, David Hildenbrand, Laurent Vivier,
Markus Armbruster, Raphael Norwitz, Richard Henderson, Fam Zheng,
sgarzare, Alberto Faria, Kevin Wolf, Stefan Hajnoczi,
Wen Congyang, Eric Blake, Hanna Reitz,
Philippe Mathieu-Daudé,
Eduardo Habkost, Michael S. Tsirkin, Thomas Huth, Jeff Cody,
Xie Changlong
v4:
- Patch 1:
- Add virtio-blk-vhost-user driver [Kevin]
- Drop .bdrv_parse_filename() and .bdrv_needs_filename for virtio-blk-vhost-vdpa [Stefano]
- Add copyright and license header [Hanna]
- Drop .bdrv_parse_filename() in favor of --blockdev or json: [Hanna]
- Clarify that "filename" is always non-NULL for io_uring [Hanna]
- Check that virtio-blk-vhost-vdpa "path" option is non-NULL [Hanna]
- Fix virtio-blk-vhost-vdpa cache.direct=off logic [Hanna]
- Use macros for driver names [Hanna]
- Assert that the driver name is valid [Hanna]
- Update "readonly" property name to "read-only" [Hanna]
- Call blkio_detach_aio_context() in blkio_close() [Hanna]
- Avoid uint32_t * to int * casts in blkio_refresh_limits() [Hanna]
- Remove write zeroes and discard from the todo list [Hanna]
- Use PRIu32 instead of %d for uint32_t [Hanna]
- Fix error messages with buf-alignment instead of optimal-io-size [Hanna]
- Call map/unmap APIs since libblkio alloc/free APIs no longer do that
- Update QAPI schema QEMU version to 7.2
- Patch 5:
- Expand the BDRV_REQ_REGISTERED_BUF flag passthrough and drop assert(!flags)
in drivers [Hanna]
- Patch 7:
- Fix BLK->BDRV typo [Hanna]
- Make BlockRAMRegistrar handle failure [Hanna]
- Patch 8:
- Replace memory_region_get_fd() approach with qemu_ram_get_fd()
- Patch 10:
- Use (void)ret; to discard unused return value [Hanna]
- libblkio's blkio_unmap_mem_region() API no longer has a return value
- Check for registered bufs that cross RAMBlocks [Hanna]
- Patch 11:
- Handle bdrv_register_buf() errors [Hanna]
v3:
- Add virtio-blk-vhost-vdpa for vdpa-blk devices including VDUSE
- Add discard and write zeroes support
- Rebase and adopt latest libblkio APIs
v2:
- Add BDRV_REQ_REGISTERED_BUF to bs.supported_write_flags [Stefano]
- Use new blkioq_get_num_completions() API
- Implement .bdrv_refresh_limits()
This patch series adds a QEMU BlockDriver for libblkio
(https://gitlab.com/libblkio/libblkio/), a library for high-performance block
device I/O.
The first patch adds the core BlockDriver and most of the libblkio API usage.
Three libblkio drivers are included:
- io_uring
- virtio-blk-vhost-user
- virtio-blk-vhost-vdpa
The remainder of the patch series reworks the existing QEMU bdrv_register_buf()
API so virtio-blk emulation efficiently map guest RAM for libblkio - some
libblkio drivers require that I/O buffer memory is pre-registered (think VFIO,
vhost, etc).
This block driver is functional enough to boot guests. The libblkio 1.0 release
is expected soon and I will drop the "RFC" once the API is stable.
See the BlockDriver struct in block/blkio.c for a list of APIs that still need
to be implemented. The core functionality is covered.
Regarding the design: each libblkio driver is a separately named BlockDriver.
That means there is an "io_uring" BlockDriver and not a generic "libblkio"
BlockDriver. This way QAPI and open parameters are type-safe and mandatory
parameters can be checked by QEMU.
Stefan Hajnoczi (11):
blkio: add libblkio block driver
numa: call ->ram_block_removed() in ram_block_notifer_remove()
block: pass size to bdrv_unregister_buf()
block: use BdrvRequestFlags type for supported flag fields
block: add BDRV_REQ_REGISTERED_BUF request flag
block: return errors from bdrv_register_buf()
block: add BlockRAMRegistrar
exec/cpu-common: add qemu_ram_get_fd()
stubs: add qemu_ram_block_from_host() and qemu_ram_get_fd()
blkio: implement BDRV_REQ_REGISTERED_BUF optimization
virtio-blk: use BDRV_REQ_REGISTERED_BUF optimization hint
MAINTAINERS | 7 +
meson_options.txt | 2 +
qapi/block-core.json | 53 +-
meson.build | 9 +
include/block/block-common.h | 9 +
include/block/block-global-state.h | 10 +-
include/block/block_int-common.h | 15 +-
include/exec/cpu-common.h | 1 +
include/hw/virtio/virtio-blk.h | 2 +
include/sysemu/block-backend-global-state.h | 4 +-
include/sysemu/block-ram-registrar.h | 37 +
block.c | 14 +
block/blkio.c | 861 ++++++++++++++++++++
block/blkverify.c | 4 +-
block/block-backend.c | 8 +-
block/block-ram-registrar.c | 54 ++
block/crypto.c | 4 +-
block/file-posix.c | 1 -
block/gluster.c | 1 -
block/io.c | 101 ++-
block/mirror.c | 2 +
block/nbd.c | 1 -
block/nvme.c | 20 +-
block/parallels.c | 1 -
block/qcow.c | 2 -
block/qed.c | 1 -
block/raw-format.c | 2 +
block/replication.c | 1 -
block/ssh.c | 1 -
block/vhdx.c | 1 -
hw/block/virtio-blk.c | 39 +-
hw/core/numa.c | 17 +
qemu-img.c | 6 +-
softmmu/physmem.c | 5 +
stubs/physmem.c | 13 +
tests/qtest/modules-test.c | 3 +
util/vfio-helpers.c | 5 +-
block/meson.build | 2 +
scripts/meson-buildoptions.sh | 3 +
stubs/meson.build | 1 +
40 files changed, 1236 insertions(+), 87 deletions(-)
create mode 100644 include/sysemu/block-ram-registrar.h
create mode 100644 block/blkio.c
create mode 100644 block/block-ram-registrar.c
create mode 100644 stubs/physmem.c
--
2.37.2
^ permalink raw reply [flat|nested] 23+ messages in thread
* [RFC v4 01/11] blkio: add libblkio block driver
2022-08-22 22:23 [RFC v4 00/11] blkio: add libblkio BlockDriver Stefan Hajnoczi
@ 2022-08-22 22:23 ` Stefan Hajnoczi
2022-08-30 7:30 ` Markus Armbruster
2022-08-22 22:23 ` [RFC v4 02/11] numa: call ->ram_block_removed() in ram_block_notifer_remove() Stefan Hajnoczi
` (10 subsequent siblings)
11 siblings, 1 reply; 23+ messages in thread
From: Stefan Hajnoczi @ 2022-08-22 22:23 UTC (permalink / raw)
To: qemu-devel
Cc: Paolo Bonzini, Denis V. Lunev, Peter Xu, Yanan Wang,
Marcel Apfelbaum, Richard W.M. Jones, qemu-block, John Snow,
integration, Vladimir Sementsov-Ogievskiy,
Vladimir Sementsov-Ogievskiy, David Hildenbrand, Laurent Vivier,
Markus Armbruster, Raphael Norwitz, Richard Henderson, Fam Zheng,
sgarzare, Alberto Faria, Kevin Wolf, Stefan Hajnoczi,
Wen Congyang, Eric Blake, Hanna Reitz,
Philippe Mathieu-Daudé,
Eduardo Habkost, Michael S. Tsirkin, Thomas Huth, Jeff Cody,
Xie Changlong
libblkio (https://gitlab.com/libblkio/libblkio/) is a library for
high-performance disk I/O. It currently supports io_uring,
virtio-blk-vhost-user, and virtio-blk-vhost-vdpa with additional drivers
under development.
One of the reasons for developing libblkio is that other applications
besides QEMU can use it. This will be particularly useful for
virtio-blk-vhost-user which applications may wish to use for connecting
to qemu-storage-daemon.
libblkio also gives us an opportunity to develop in Rust behind a C API
that is easy to consume from QEMU.
This commit adds io_uring, virtio-blk-vhost-user, and
virtio-blk-vhost-vdpa BlockDrivers to QEMU using libblkio. It will be
easy to add other libblkio drivers since they will share the majority of
code.
For now I/O buffers are copied through bounce buffers if the libblkio
driver requires it. Later commits add an optimization for
pre-registering guest RAM to avoid bounce buffers.
The syntax is:
--blockdev io_uring,node-name=drive0,filename=test.img,readonly=on|off,cache.direct=on|off
and:
--blockdev virtio-blk-vhost-vdpa,node-name=drive0,path=/dev/vdpa...,readonly=on|off
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
MAINTAINERS | 6 +
meson_options.txt | 2 +
qapi/block-core.json | 53 ++-
meson.build | 9 +
block/blkio.c | 725 ++++++++++++++++++++++++++++++++++
tests/qtest/modules-test.c | 3 +
block/meson.build | 1 +
scripts/meson-buildoptions.sh | 3 +
8 files changed, 800 insertions(+), 2 deletions(-)
create mode 100644 block/blkio.c
diff --git a/MAINTAINERS b/MAINTAINERS
index 5ce4227ff6..f8ccd5954c 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -3397,6 +3397,12 @@ L: qemu-block@nongnu.org
S: Maintained
F: block/vdi.c
+blkio
+M: Stefan Hajnoczi <stefanha@redhat.com>
+L: qemu-block@nongnu.org
+S: Maintained
+F: block/blkio.c
+
iSCSI
M: Ronnie Sahlberg <ronniesahlberg@gmail.com>
M: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/meson_options.txt b/meson_options.txt
index e58e158396..67d841a8d2 100644
--- a/meson_options.txt
+++ b/meson_options.txt
@@ -117,6 +117,8 @@ option('bzip2', type : 'feature', value : 'auto',
description: 'bzip2 support for DMG images')
option('cap_ng', type : 'feature', value : 'auto',
description: 'cap_ng support')
+option('blkio', type : 'feature', value : 'auto',
+ description: 'libblkio block device driver')
option('bpf', type : 'feature', value : 'auto',
description: 'eBPF support')
option('cocoa', type : 'feature', value : 'auto',
diff --git a/qapi/block-core.json b/qapi/block-core.json
index 2173e7734a..c8d217b50c 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -2951,11 +2951,16 @@
'file', 'snapshot-access', 'ftp', 'ftps', 'gluster',
{'name': 'host_cdrom', 'if': 'HAVE_HOST_BLOCK_DEVICE' },
{'name': 'host_device', 'if': 'HAVE_HOST_BLOCK_DEVICE' },
- 'http', 'https', 'iscsi',
+ 'http', 'https',
+ { 'name': 'io_uring', 'if': 'CONFIG_BLKIO' },
+ 'iscsi',
'luks', 'nbd', 'nfs', 'null-aio', 'null-co', 'nvme', 'parallels',
'preallocate', 'qcow', 'qcow2', 'qed', 'quorum', 'raw', 'rbd',
{ 'name': 'replication', 'if': 'CONFIG_REPLICATION' },
- 'ssh', 'throttle', 'vdi', 'vhdx', 'vmdk', 'vpc', 'vvfat' ] }
+ 'ssh', 'throttle', 'vdi', 'vhdx',
+ { 'name': 'virtio-blk-vhost-user', 'if': 'CONFIG_BLKIO' },
+ { 'name': 'virtio-blk-vhost-vdpa', 'if': 'CONFIG_BLKIO' },
+ 'vmdk', 'vpc', 'vvfat' ] }
##
# @BlockdevOptionsFile:
@@ -3678,6 +3683,42 @@
'*debug': 'int',
'*logfile': 'str' } }
+##
+# @BlockdevOptionsIoUring:
+#
+# Driver specific block device options for the io_uring backend.
+#
+# @filename: path to the image file
+#
+# Since: 7.2
+##
+{ 'struct': 'BlockdevOptionsIoUring',
+ 'data': { 'filename': 'str' } }
+
+##
+# @BlockdevOptionsVirtioBlkVhostUser:
+#
+# Driver specific block device options for the virtio-blk-vhost-user backend.
+#
+# @path: path to the vhost-user UNIX domain socket.
+#
+# Since: 7.2
+##
+{ 'struct': 'BlockdevOptionsVirtioBlkVhostUser',
+ 'data': { 'path': 'str' } }
+
+##
+# @BlockdevOptionsVirtioBlkVhostVdpa:
+#
+# Driver specific block device options for the virtio-blk-vhost-vdpa backend.
+#
+# @path: path to the vhost-vdpa character device.
+#
+# Since: 7.2
+##
+{ 'struct': 'BlockdevOptionsVirtioBlkVhostVdpa',
+ 'data': { 'path': 'str' } }
+
##
# @IscsiTransport:
#
@@ -4305,6 +4346,8 @@
'if': 'HAVE_HOST_BLOCK_DEVICE' },
'http': 'BlockdevOptionsCurlHttp',
'https': 'BlockdevOptionsCurlHttps',
+ 'io_uring': { 'type': 'BlockdevOptionsIoUring',
+ 'if': 'CONFIG_BLKIO' },
'iscsi': 'BlockdevOptionsIscsi',
'luks': 'BlockdevOptionsLUKS',
'nbd': 'BlockdevOptionsNbd',
@@ -4327,6 +4370,12 @@
'throttle': 'BlockdevOptionsThrottle',
'vdi': 'BlockdevOptionsGenericFormat',
'vhdx': 'BlockdevOptionsGenericFormat',
+ 'virtio-blk-vhost-user':
+ { 'type': 'BlockdevOptionsVirtioBlkVhostUser',
+ 'if': 'CONFIG_BLKIO' },
+ 'virtio-blk-vhost-vdpa':
+ { 'type': 'BlockdevOptionsVirtioBlkVhostVdpa',
+ 'if': 'CONFIG_BLKIO' },
'vmdk': 'BlockdevOptionsGenericCOWFormat',
'vpc': 'BlockdevOptionsGenericFormat',
'vvfat': 'BlockdevOptionsVVFAT'
diff --git a/meson.build b/meson.build
index 20fddbd707..c0280c076d 100644
--- a/meson.build
+++ b/meson.build
@@ -719,6 +719,13 @@ if not get_option('virglrenderer').auto() or have_system or have_vhost_user_gpu
required: get_option('virglrenderer'),
kwargs: static_kwargs)
endif
+blkio = not_found
+if not get_option('blkio').auto() or have_block
+ blkio = dependency('blkio',
+ method: 'pkg-config',
+ required: get_option('blkio'),
+ kwargs: static_kwargs)
+endif
curl = not_found
if not get_option('curl').auto() or have_block
curl = dependency('libcurl', version: '>=7.29.0',
@@ -1769,6 +1776,7 @@ config_host_data.set('CONFIG_LIBUDEV', libudev.found())
config_host_data.set('CONFIG_LZO', lzo.found())
config_host_data.set('CONFIG_MPATH', mpathpersist.found())
config_host_data.set('CONFIG_MPATH_NEW_API', mpathpersist_new_api)
+config_host_data.set('CONFIG_BLKIO', blkio.found())
config_host_data.set('CONFIG_CURL', curl.found())
config_host_data.set('CONFIG_CURSES', curses.found())
config_host_data.set('CONFIG_GBM', gbm.found())
@@ -3917,6 +3925,7 @@ summary_info += {'PAM': pam}
summary_info += {'iconv support': iconv}
summary_info += {'curses support': curses}
summary_info += {'virgl support': virgl}
+summary_info += {'blkio support': blkio}
summary_info += {'curl support': curl}
summary_info += {'Multipath support': mpathpersist}
summary_info += {'PNG support': png}
diff --git a/block/blkio.c b/block/blkio.c
new file mode 100644
index 0000000000..cdcba1b63e
--- /dev/null
+++ b/block/blkio.c
@@ -0,0 +1,725 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * libblkio BlockDriver
+ *
+ * Copyright Red Hat, Inc.
+ *
+ * Author:
+ * Stefan Hajnoczi <stefanha@redhat.com>
+ */
+
+#include "qemu/osdep.h"
+#include <blkio.h>
+#include "block/block_int.h"
+#include "qapi/error.h"
+#include "qapi/qmp/qdict.h"
+#include "qemu/module.h"
+
+/*
+ * Keep the QEMU BlockDriver names identical to the libblkio driver names.
+ * Using macros instead of typing out the string literals avoids typos.
+ */
+#define DRIVER_IO_URING "io_uring"
+#define DRIVER_VIRTIO_BLK_VHOST_USER "virtio-blk-vhost-user"
+#define DRIVER_VIRTIO_BLK_VHOST_VDPA "virtio-blk-vhost-vdpa"
+
+typedef struct BlkAIOCB {
+ BlockAIOCB common;
+ struct blkio_mem_region mem_region;
+ QEMUIOVector qiov;
+ struct iovec bounce_iov;
+} BlkioAIOCB;
+
+typedef struct {
+ /* Protects ->blkio and request submission on ->blkioq */
+ QemuMutex lock;
+
+ struct blkio *blkio;
+ struct blkioq *blkioq; /* this could be multi-queue in the future */
+ int completion_fd;
+
+ /* Polling fetches the next completion into this field */
+ struct blkio_completion poll_completion;
+
+ /* The value of the "mem-region-alignment" property */
+ size_t mem_region_alignment;
+
+ /* Can we skip adding/deleting blkio_mem_regions? */
+ bool needs_mem_regions;
+} BDRVBlkioState;
+
+static void blkio_aiocb_complete(BlkioAIOCB *acb, int ret)
+{
+ /* Copy bounce buffer back to qiov */
+ if (acb->qiov.niov > 0) {
+ qemu_iovec_from_buf(&acb->qiov, 0,
+ acb->bounce_iov.iov_base,
+ acb->bounce_iov.iov_len);
+ qemu_iovec_destroy(&acb->qiov);
+ }
+
+ acb->common.cb(acb->common.opaque, ret);
+
+ if (acb->mem_region.len > 0) {
+ BDRVBlkioState *s = acb->common.bs->opaque;
+
+ WITH_QEMU_LOCK_GUARD(&s->lock) {
+ blkio_unmap_mem_region(s->blkio, &acb->mem_region);
+ blkio_free_mem_region(s->blkio, &acb->mem_region);
+ }
+ }
+
+ qemu_aio_unref(&acb->common);
+}
+
+/*
+ * Only the thread that calls aio_poll() invokes fd and poll handlers.
+ * Therefore locks are not necessary except when accessing s->blkio.
+ *
+ * No locking is performed around blkioq_get_completions() although other
+ * threads may submit I/O requests on s->blkioq. We're assuming there is no
+ * inteference between blkioq_get_completions() and other s->blkioq APIs.
+ */
+
+static void blkio_completion_fd_read(void *opaque)
+{
+ BlockDriverState *bs = opaque;
+ BDRVBlkioState *s = bs->opaque;
+ struct blkio_completion completion;
+ uint64_t val;
+ int ret;
+
+ /* Polling may have already fetched a completion */
+ if (s->poll_completion.user_data != NULL) {
+ completion = s->poll_completion;
+
+ /* Clear it in case blkio_aiocb_complete() has a nested event loop */
+ s->poll_completion.user_data = NULL;
+
+ blkio_aiocb_complete(completion.user_data, completion.ret);
+ }
+
+ /* Reset completion fd status */
+ ret = read(s->completion_fd, &val, sizeof(val));
+
+ /* Ignore errors, there's nothing we can do */
+ (void)ret;
+
+ /*
+ * Reading one completion at a time makes nested event loop re-entrancy
+ * simple. Change this loop to get multiple completions in one go if it
+ * becomes a performance bottleneck.
+ */
+ while (blkioq_do_io(s->blkioq, &completion, 0, 1, NULL) == 1) {
+ blkio_aiocb_complete(completion.user_data, completion.ret);
+ }
+}
+
+static bool blkio_completion_fd_poll(void *opaque)
+{
+ BlockDriverState *bs = opaque;
+ BDRVBlkioState *s = bs->opaque;
+
+ /* Just in case we already fetched a completion */
+ if (s->poll_completion.user_data != NULL) {
+ return true;
+ }
+
+ return blkioq_do_io(s->blkioq, &s->poll_completion, 0, 1, NULL) == 1;
+}
+
+static void blkio_completion_fd_poll_ready(void *opaque)
+{
+ blkio_completion_fd_read(opaque);
+}
+
+static void blkio_attach_aio_context(BlockDriverState *bs,
+ AioContext *new_context)
+{
+ BDRVBlkioState *s = bs->opaque;
+
+ aio_set_fd_handler(new_context,
+ s->completion_fd,
+ false,
+ blkio_completion_fd_read,
+ NULL,
+ blkio_completion_fd_poll,
+ blkio_completion_fd_poll_ready,
+ bs);
+}
+
+static void blkio_detach_aio_context(BlockDriverState *bs)
+{
+ BDRVBlkioState *s = bs->opaque;
+
+ aio_set_fd_handler(bdrv_get_aio_context(bs),
+ s->completion_fd,
+ false, NULL, NULL, NULL, NULL, NULL);
+}
+
+static const AIOCBInfo blkio_aiocb_info = {
+ .aiocb_size = sizeof(BlkioAIOCB),
+};
+
+/* Create a BlkioAIOCB */
+static BlkioAIOCB *blkio_aiocb_get(BlockDriverState *bs,
+ BlockCompletionFunc *cb,
+ void *opaque)
+{
+ BlkioAIOCB *acb = qemu_aio_get(&blkio_aiocb_info, bs, cb, opaque);
+
+ /* A few fields need to be initialized, leave the rest... */
+ acb->qiov.niov = 0;
+ acb->mem_region.len = 0;
+ return acb;
+}
+
+/* s->lock must be held */
+static int blkio_aiocb_init_mem_region_locked(BlkioAIOCB *acb, size_t len)
+{
+ BDRVBlkioState *s = acb->common.bs->opaque;
+ size_t mem_region_len = QEMU_ALIGN_UP(len, s->mem_region_alignment);
+ int ret;
+
+ ret = blkio_alloc_mem_region(s->blkio, &acb->mem_region, mem_region_len);
+ if (ret < 0) {
+ return ret;
+ }
+
+ ret = blkio_map_mem_region(s->blkio, &acb->mem_region);
+ if (ret < 0) {
+ blkio_free_mem_region(s->blkio, &acb->mem_region);
+ return ret;
+ }
+
+ acb->bounce_iov.iov_base = acb->mem_region.addr;
+ acb->bounce_iov.iov_len = len;
+ return 0;
+}
+
+/* Call this to submit I/O after enqueuing a new request */
+static void blkio_submit_io(BlockDriverState *bs)
+{
+ if (qatomic_read(&bs->io_plugged) == 0) {
+ BDRVBlkioState *s = bs->opaque;
+
+ blkioq_do_io(s->blkioq, NULL, 0, 0, NULL);
+ }
+}
+
+static BlockAIOCB *blkio_aio_pdiscard(BlockDriverState *bs, int64_t offset,
+ int bytes, BlockCompletionFunc *cb, void *opaque)
+{
+ BDRVBlkioState *s = bs->opaque;
+ BlkioAIOCB *acb;
+
+ QEMU_LOCK_GUARD(&s->lock);
+
+ acb = blkio_aiocb_get(bs, cb, opaque);
+ blkioq_discard(s->blkioq, offset, bytes, acb, 0);
+ blkio_submit_io(bs);
+ return &acb->common;
+}
+
+static BlockAIOCB *blkio_aio_preadv(BlockDriverState *bs, int64_t offset,
+ int64_t bytes, QEMUIOVector *qiov, BdrvRequestFlags flags,
+ BlockCompletionFunc *cb, void *opaque)
+{
+ BDRVBlkioState *s = bs->opaque;
+ struct iovec *iov = qiov->iov;
+ int iovcnt = qiov->niov;
+ BlkioAIOCB *acb;
+
+ QEMU_LOCK_GUARD(&s->lock);
+
+ acb = blkio_aiocb_get(bs, cb, opaque);
+
+ if (s->needs_mem_regions) {
+ if (blkio_aiocb_init_mem_region_locked(acb, bytes) < 0) {
+ qemu_aio_unref(&acb->common);
+ return NULL;
+ }
+
+ /* Copy qiov because we'll call qemu_iovec_from_buf() on completion */
+ qemu_iovec_init_slice(&acb->qiov, qiov, 0, qiov->size);
+
+ iov = &acb->bounce_iov;
+ iovcnt = 1;
+ }
+
+ blkioq_readv(s->blkioq, offset, iov, iovcnt, acb, 0);
+ blkio_submit_io(bs);
+ return &acb->common;
+}
+
+static BlockAIOCB *blkio_aio_pwritev(BlockDriverState *bs, int64_t offset,
+ int64_t bytes, QEMUIOVector *qiov, BdrvRequestFlags flags,
+ BlockCompletionFunc *cb, void *opaque)
+{
+ uint32_t blkio_flags = (flags & BDRV_REQ_FUA) ? BLKIO_REQ_FUA : 0;
+ BDRVBlkioState *s = bs->opaque;
+ struct iovec *iov = qiov->iov;
+ int iovcnt = qiov->niov;
+ BlkioAIOCB *acb;
+
+ QEMU_LOCK_GUARD(&s->lock);
+
+ acb = blkio_aiocb_get(bs, cb, opaque);
+
+ if (s->needs_mem_regions) {
+ if (blkio_aiocb_init_mem_region_locked(acb, bytes) < 0) {
+ qemu_aio_unref(&acb->common);
+ return NULL;
+ }
+
+ qemu_iovec_to_buf(qiov, 0, acb->bounce_iov.iov_base, bytes);
+
+ iov = &acb->bounce_iov;
+ iovcnt = 1;
+ }
+
+ blkioq_writev(s->blkioq, offset, iov, iovcnt, acb, blkio_flags);
+ blkio_submit_io(bs);
+ return &acb->common;
+}
+
+static BlockAIOCB *blkio_aio_flush(BlockDriverState *bs,
+ BlockCompletionFunc *cb,
+ void *opaque)
+{
+ BDRVBlkioState *s = bs->opaque;
+ BlkioAIOCB *acb;
+
+ QEMU_LOCK_GUARD(&s->lock);
+
+ acb = blkio_aiocb_get(bs, cb, opaque);
+
+ blkioq_flush(s->blkioq, acb, 0);
+ blkio_submit_io(bs);
+ return &acb->common;
+}
+
+/* For async to .bdrv_co_*() conversion */
+typedef struct {
+ Coroutine *coroutine;
+ int ret;
+} BlkioCoData;
+
+static void blkio_co_pwrite_zeroes_complete(void *opaque, int ret)
+{
+ BlkioCoData *data = opaque;
+
+ data->ret = ret;
+ aio_co_wake(data->coroutine);
+}
+
+static int coroutine_fn blkio_co_pwrite_zeroes(BlockDriverState *bs,
+ int64_t offset, int64_t bytes, BdrvRequestFlags flags)
+{
+ BDRVBlkioState *s = bs->opaque;
+ BlkioCoData data = {
+ .coroutine = qemu_coroutine_self(),
+ };
+ uint32_t blkio_flags = 0;
+
+ if (flags & BDRV_REQ_FUA) {
+ blkio_flags |= BLKIO_REQ_FUA;
+ }
+ if (!(flags & BDRV_REQ_MAY_UNMAP)) {
+ blkio_flags |= BLKIO_REQ_NO_UNMAP;
+ }
+ if (flags & BDRV_REQ_NO_FALLBACK) {
+ blkio_flags |= BLKIO_REQ_NO_FALLBACK;
+ }
+
+ WITH_QEMU_LOCK_GUARD(&s->lock) {
+ BlkioAIOCB *acb =
+ blkio_aiocb_get(bs, blkio_co_pwrite_zeroes_complete, &data);
+ blkioq_write_zeroes(s->blkioq, offset, bytes, acb, blkio_flags);
+ blkio_submit_io(bs);
+ }
+
+ qemu_coroutine_yield();
+ return data.ret;
+}
+
+static void blkio_io_unplug(BlockDriverState *bs)
+{
+ BDRVBlkioState *s = bs->opaque;
+
+ WITH_QEMU_LOCK_GUARD(&s->lock) {
+ blkio_submit_io(bs);
+ }
+}
+
+static int blkio_io_uring_open(BlockDriverState *bs, QDict *options, int flags,
+ Error **errp)
+{
+ const char *filename = qdict_get_str(options, "filename");
+ BDRVBlkioState *s = bs->opaque;
+ int ret;
+
+ ret = blkio_set_str(s->blkio, "path", filename);
+ qdict_del(options, "filename");
+ if (ret < 0) {
+ error_setg_errno(errp, -ret, "failed to set path: %s",
+ blkio_get_error_msg());
+ return ret;
+ }
+
+ if (flags & BDRV_O_NOCACHE) {
+ ret = blkio_set_bool(s->blkio, "direct", true);
+ if (ret < 0) {
+ error_setg_errno(errp, -ret, "failed to set direct: %s",
+ blkio_get_error_msg());
+ return ret;
+ }
+ }
+
+ return 0;
+}
+
+static int blkio_virtio_blk_vhost_user_open(BlockDriverState *bs,
+ QDict *options, int flags, Error **errp)
+{
+ const char *path = qdict_get_try_str(options, "path");
+ BDRVBlkioState *s = bs->opaque;
+ int ret;
+
+ if (!path) {
+ error_setg(errp, "missing 'path' option");
+ return -EINVAL;
+ }
+
+ ret = blkio_set_str(s->blkio, "path", path);
+ qdict_del(options, "path");
+ if (ret < 0) {
+ error_setg_errno(errp, -ret, "failed to set path: %s",
+ blkio_get_error_msg());
+ return ret;
+ }
+
+ if (!(flags & BDRV_O_NOCACHE)) {
+ error_setg(errp, "cache.direct=off is not supported");
+ return -EINVAL;
+ }
+ return 0;
+}
+
+static int blkio_virtio_blk_vhost_vdpa_open(BlockDriverState *bs,
+ QDict *options, int flags, Error **errp)
+{
+ const char *path = qdict_get_try_str(options, "path");
+ BDRVBlkioState *s = bs->opaque;
+ int ret;
+
+ if (!path) {
+ error_setg(errp, "missing 'path' option");
+ return -EINVAL;
+ }
+
+ ret = blkio_set_str(s->blkio, "path", path);
+ qdict_del(options, "path");
+ if (ret < 0) {
+ error_setg_errno(errp, -ret, "failed to set path: %s",
+ blkio_get_error_msg());
+ return ret;
+ }
+
+ if (!(flags & BDRV_O_NOCACHE)) {
+ error_setg(errp, "cache.direct=off is not supported");
+ return -EINVAL;
+ }
+ return 0;
+}
+
+static int blkio_file_open(BlockDriverState *bs, QDict *options, int flags,
+ Error **errp)
+{
+ const char *blkio_driver = bs->drv->protocol_name;
+ BDRVBlkioState *s = bs->opaque;
+ int ret;
+
+ ret = blkio_create(blkio_driver, &s->blkio);
+ if (ret < 0) {
+ error_setg_errno(errp, -ret, "blkio_create failed: %s",
+ blkio_get_error_msg());
+ return ret;
+ }
+
+ if (strcmp(blkio_driver, DRIVER_IO_URING) == 0) {
+ ret = blkio_io_uring_open(bs, options, flags, errp);
+ } else if (strcmp(blkio_driver, DRIVER_VIRTIO_BLK_VHOST_USER) == 0) {
+ ret = blkio_virtio_blk_vhost_user_open(bs, options, flags, errp);
+ } else if (strcmp(blkio_driver, DRIVER_VIRTIO_BLK_VHOST_VDPA) == 0) {
+ ret = blkio_virtio_blk_vhost_vdpa_open(bs, options, flags, errp);
+ } else {
+ g_assert_not_reached();
+ }
+ if (ret < 0) {
+ blkio_destroy(&s->blkio);
+ return ret;
+ }
+
+ if (!(flags & BDRV_O_RDWR)) {
+ ret = blkio_set_bool(s->blkio, "read-only", true);
+ if (ret < 0) {
+ error_setg_errno(errp, -ret, "failed to set read-only: %s",
+ blkio_get_error_msg());
+ blkio_destroy(&s->blkio);
+ return ret;
+ }
+ }
+
+ ret = blkio_connect(s->blkio);
+ if (ret < 0) {
+ error_setg_errno(errp, -ret, "blkio_connect failed: %s",
+ blkio_get_error_msg());
+ blkio_destroy(&s->blkio);
+ return ret;
+ }
+
+ ret = blkio_get_bool(s->blkio,
+ "needs-mem-regions",
+ &s->needs_mem_regions);
+ if (ret < 0) {
+ error_setg_errno(errp, -ret,
+ "failed to get needs-mem-regions: %s",
+ blkio_get_error_msg());
+ blkio_destroy(&s->blkio);
+ return ret;
+ }
+
+ ret = blkio_get_uint64(s->blkio,
+ "mem-region-alignment",
+ &s->mem_region_alignment);
+ if (ret < 0) {
+ error_setg_errno(errp, -ret,
+ "failed to get mem-region-alignment: %s",
+ blkio_get_error_msg());
+ blkio_destroy(&s->blkio);
+ return ret;
+ }
+
+ ret = blkio_start(s->blkio);
+ if (ret < 0) {
+ error_setg_errno(errp, -ret, "blkio_start failed: %s",
+ blkio_get_error_msg());
+ blkio_destroy(&s->blkio);
+ return ret;
+ }
+
+ bs->supported_write_flags = BDRV_REQ_FUA;
+ bs->supported_zero_flags = BDRV_REQ_FUA | BDRV_REQ_MAY_UNMAP |
+ BDRV_REQ_NO_FALLBACK;
+
+ qemu_mutex_init(&s->lock);
+ s->blkioq = blkio_get_queue(s->blkio, 0);
+ s->completion_fd = blkioq_get_completion_fd(s->blkioq);
+
+ blkio_attach_aio_context(bs, bdrv_get_aio_context(bs));
+ return 0;
+}
+
+static void blkio_close(BlockDriverState *bs)
+{
+ BDRVBlkioState *s = bs->opaque;
+
+ qemu_mutex_destroy(&s->lock);
+ blkio_detach_aio_context(bs);
+ blkio_destroy(&s->blkio);
+}
+
+static int64_t blkio_getlength(BlockDriverState *bs)
+{
+ BDRVBlkioState *s = bs->opaque;
+ uint64_t capacity;
+ int ret;
+
+ WITH_QEMU_LOCK_GUARD(&s->lock) {
+ ret = blkio_get_uint64(s->blkio, "capacity", &capacity);
+ }
+ if (ret < 0) {
+ return -ret;
+ }
+
+ return capacity;
+}
+
+static int blkio_get_info(BlockDriverState *bs, BlockDriverInfo *bdi)
+{
+ return 0;
+}
+
+static void blkio_refresh_limits(BlockDriverState *bs, Error **errp)
+{
+ BDRVBlkioState *s = bs->opaque;
+ int value;
+ int ret;
+
+ ret = blkio_get_int(s->blkio, "request-alignment", &value);
+ if (ret < 0) {
+ error_setg_errno(errp, -ret, "failed to get \"request-alignment\": %s",
+ blkio_get_error_msg());
+ return;
+ }
+ bs->bl.request_alignment = value;
+ if (bs->bl.request_alignment < 1 ||
+ bs->bl.request_alignment >= INT_MAX ||
+ !is_power_of_2(bs->bl.request_alignment)) {
+ error_setg(errp, "invalid \"request-alignment\" value %" PRIu32 ", "
+ "must be a power of 2 less than INT_MAX",
+ bs->bl.request_alignment);
+ return;
+ }
+
+ ret = blkio_get_int(s->blkio, "optimal-io-size", &value);
+ if (ret < 0) {
+ error_setg_errno(errp, -ret, "failed to get \"optimal-io-size\": %s",
+ blkio_get_error_msg());
+ return;
+ }
+ bs->bl.opt_transfer = value;
+ if (bs->bl.opt_transfer > INT_MAX ||
+ (bs->bl.opt_transfer % bs->bl.request_alignment)) {
+ error_setg(errp, "invalid \"optimal-io-size\" value %" PRIu32 ", must "
+ "be a multiple of %" PRIu32, bs->bl.opt_transfer,
+ bs->bl.request_alignment);
+ return;
+ }
+
+ ret = blkio_get_int(s->blkio, "max-transfer", &value);
+ if (ret < 0) {
+ error_setg_errno(errp, -ret, "failed to get \"max-transfer\": %s",
+ blkio_get_error_msg());
+ return;
+ }
+ bs->bl.max_transfer = value;
+ if ((bs->bl.max_transfer % bs->bl.request_alignment) ||
+ (bs->bl.opt_transfer && (bs->bl.max_transfer % bs->bl.opt_transfer))) {
+ error_setg(errp, "invalid \"max-transfer\" value %" PRIu32 ", must be "
+ "a multiple of %" PRIu32 " and %" PRIu32 " (if non-zero)",
+ bs->bl.max_transfer, bs->bl.request_alignment,
+ bs->bl.opt_transfer);
+ return;
+ }
+
+ ret = blkio_get_int(s->blkio, "buf-alignment", &value);
+ if (ret < 0) {
+ error_setg_errno(errp, -ret, "failed to get \"buf-alignment\": %s",
+ blkio_get_error_msg());
+ return;
+ }
+ if (value < 1) {
+ error_setg(errp, "invalid \"buf-alignment\" value %d, must be "
+ "positive", value);
+ return;
+ }
+ bs->bl.min_mem_alignment = value;
+
+ ret = blkio_get_int(s->blkio, "optimal-buf-alignment", &value);
+ if (ret < 0) {
+ error_setg_errno(errp, -ret,
+ "failed to get \"optimal-buf-alignment\": %s",
+ blkio_get_error_msg());
+ return;
+ }
+ if (value < 1) {
+ error_setg(errp, "invalid \"optimal-buf-alignment\" value %d, "
+ "must be positive", value);
+ return;
+ }
+ bs->bl.opt_mem_alignment = value;
+
+ ret = blkio_get_int(s->blkio, "max-segments", &bs->bl.max_iov);
+ if (ret < 0) {
+ error_setg_errno(errp, -ret, "failed to get \"max-segments\": %s",
+ blkio_get_error_msg());
+ return;
+ }
+ if (value < 1) {
+ error_setg(errp, "invalid \"max-segments\" value %d, must be positive",
+ bs->bl.max_iov);
+ return;
+ }
+}
+
+/*
+ * TODO
+ * Missing libblkio APIs:
+ * - block_status
+ * - co_invalidate_cache
+ *
+ * Out of scope?
+ * - create
+ * - truncate
+ */
+
+static BlockDriver bdrv_io_uring = {
+ .format_name = DRIVER_IO_URING,
+ .protocol_name = DRIVER_IO_URING,
+ .instance_size = sizeof(BDRVBlkioState),
+ .bdrv_needs_filename = true,
+ .bdrv_file_open = blkio_file_open,
+ .bdrv_close = blkio_close,
+ .bdrv_getlength = blkio_getlength,
+ .bdrv_get_info = blkio_get_info,
+ .bdrv_attach_aio_context = blkio_attach_aio_context,
+ .bdrv_detach_aio_context = blkio_detach_aio_context,
+ .bdrv_aio_pdiscard = blkio_aio_pdiscard,
+ .bdrv_aio_preadv = blkio_aio_preadv,
+ .bdrv_aio_pwritev = blkio_aio_pwritev,
+ .bdrv_aio_flush = blkio_aio_flush,
+ .bdrv_co_pwrite_zeroes = blkio_co_pwrite_zeroes,
+ .bdrv_io_unplug = blkio_io_unplug,
+ .bdrv_refresh_limits = blkio_refresh_limits,
+};
+
+static BlockDriver bdrv_virtio_blk_vhost_user = {
+ .format_name = DRIVER_VIRTIO_BLK_VHOST_USER,
+ .protocol_name = DRIVER_VIRTIO_BLK_VHOST_USER,
+ .instance_size = sizeof(BDRVBlkioState),
+ .bdrv_file_open = blkio_file_open,
+ .bdrv_close = blkio_close,
+ .bdrv_getlength = blkio_getlength,
+ .bdrv_get_info = blkio_get_info,
+ .bdrv_attach_aio_context = blkio_attach_aio_context,
+ .bdrv_detach_aio_context = blkio_detach_aio_context,
+ .bdrv_aio_pdiscard = blkio_aio_pdiscard,
+ .bdrv_aio_preadv = blkio_aio_preadv,
+ .bdrv_aio_pwritev = blkio_aio_pwritev,
+ .bdrv_aio_flush = blkio_aio_flush,
+ .bdrv_co_pwrite_zeroes = blkio_co_pwrite_zeroes,
+ .bdrv_io_unplug = blkio_io_unplug,
+ .bdrv_refresh_limits = blkio_refresh_limits,
+ .bdrv_register_buf = blkio_register_buf,
+ .bdrv_unregister_buf = blkio_unregister_buf,
+};
+
+static BlockDriver bdrv_virtio_blk_vhost_vdpa = {
+ .format_name = DRIVER_VIRTIO_BLK_VHOST_VDPA,
+ .protocol_name = DRIVER_VIRTIO_BLK_VHOST_VDPA,
+ .instance_size = sizeof(BDRVBlkioState),
+ .bdrv_file_open = blkio_file_open,
+ .bdrv_close = blkio_close,
+ .bdrv_getlength = blkio_getlength,
+ .bdrv_get_info = blkio_get_info,
+ .bdrv_attach_aio_context = blkio_attach_aio_context,
+ .bdrv_detach_aio_context = blkio_detach_aio_context,
+ .bdrv_aio_pdiscard = blkio_aio_pdiscard,
+ .bdrv_aio_preadv = blkio_aio_preadv,
+ .bdrv_aio_pwritev = blkio_aio_pwritev,
+ .bdrv_aio_flush = blkio_aio_flush,
+ .bdrv_co_pwrite_zeroes = blkio_co_pwrite_zeroes,
+ .bdrv_io_unplug = blkio_io_unplug,
+ .bdrv_refresh_limits = blkio_refresh_limits,
+};
+
+static void bdrv_blkio_init(void)
+{
+ bdrv_register(&bdrv_io_uring);
+ bdrv_register(&bdrv_virtio_blk_vhost_user);
+ bdrv_register(&bdrv_virtio_blk_vhost_vdpa);
+}
+
+block_init(bdrv_blkio_init);
diff --git a/tests/qtest/modules-test.c b/tests/qtest/modules-test.c
index 88217686e1..be2575ae6d 100644
--- a/tests/qtest/modules-test.c
+++ b/tests/qtest/modules-test.c
@@ -16,6 +16,9 @@ static void test_modules_load(const void *data)
int main(int argc, char *argv[])
{
const char *modules[] = {
+#ifdef CONFIG_BLKIO
+ "block-", "blkio",
+#endif
#ifdef CONFIG_CURL
"block-", "curl",
#endif
diff --git a/block/meson.build b/block/meson.build
index 60bc305597..500878f082 100644
--- a/block/meson.build
+++ b/block/meson.build
@@ -92,6 +92,7 @@ block_modules = {}
modsrc = []
foreach m : [
+ [blkio, 'blkio', files('blkio.c')],
[curl, 'curl', files('curl.c')],
[glusterfs, 'gluster', files('gluster.c')],
[libiscsi, 'iscsi', [files('iscsi.c'), libm]],
diff --git a/scripts/meson-buildoptions.sh b/scripts/meson-buildoptions.sh
index 359b04e0e6..965a4e0c16 100644
--- a/scripts/meson-buildoptions.sh
+++ b/scripts/meson-buildoptions.sh
@@ -69,6 +69,7 @@ meson_options_help() {
printf "%s\n" ' auth-pam PAM access control'
printf "%s\n" ' avx2 AVX2 optimizations'
printf "%s\n" ' avx512f AVX512F optimizations'
+ printf "%s\n" ' blkio libblkio block device driver'
printf "%s\n" ' bochs bochs image format support'
printf "%s\n" ' bpf eBPF support'
printf "%s\n" ' brlapi brlapi character device driver'
@@ -198,6 +199,8 @@ _meson_option_parse() {
--disable-gcov) printf "%s" -Db_coverage=false ;;
--enable-lto) printf "%s" -Db_lto=true ;;
--disable-lto) printf "%s" -Db_lto=false ;;
+ --enable-blkio) printf "%s" -Dblkio=enabled ;;
+ --disable-blkio) printf "%s" -Dblkio=disabled ;;
--block-drv-ro-whitelist=*) quote_sh "-Dblock_drv_ro_whitelist=$2" ;;
--block-drv-rw-whitelist=*) quote_sh "-Dblock_drv_rw_whitelist=$2" ;;
--enable-block-drv-whitelist-in-tools) printf "%s" -Dblock_drv_whitelist_in_tools=true ;;
--
2.37.2
^ permalink raw reply related [flat|nested] 23+ messages in thread
* [RFC v4 02/11] numa: call ->ram_block_removed() in ram_block_notifer_remove()
2022-08-22 22:23 [RFC v4 00/11] blkio: add libblkio BlockDriver Stefan Hajnoczi
2022-08-22 22:23 ` [RFC v4 01/11] blkio: add libblkio block driver Stefan Hajnoczi
@ 2022-08-22 22:23 ` Stefan Hajnoczi
2022-08-22 22:23 ` [RFC v4 03/11] block: pass size to bdrv_unregister_buf() Stefan Hajnoczi
` (9 subsequent siblings)
11 siblings, 0 replies; 23+ messages in thread
From: Stefan Hajnoczi @ 2022-08-22 22:23 UTC (permalink / raw)
To: qemu-devel
Cc: Paolo Bonzini, Denis V. Lunev, Peter Xu, Yanan Wang,
Marcel Apfelbaum, Richard W.M. Jones, qemu-block, John Snow,
integration, Vladimir Sementsov-Ogievskiy,
Vladimir Sementsov-Ogievskiy, David Hildenbrand, Laurent Vivier,
Markus Armbruster, Raphael Norwitz, Richard Henderson, Fam Zheng,
sgarzare, Alberto Faria, Kevin Wolf, Stefan Hajnoczi,
Wen Congyang, Eric Blake, Hanna Reitz,
Philippe Mathieu-Daudé,
Eduardo Habkost, Michael S. Tsirkin, Thomas Huth, Jeff Cody,
Xie Changlong
When a RAMBlockNotifier is added, ->ram_block_added() is called with all
existing RAMBlocks. There is no equivalent ->ram_block_removed() call
when a RAMBlockNotifier is removed.
The util/vfio-helpers.c code (the sole user of RAMBlockNotifier) is fine
with this asymmetry because it does not rely on RAMBlockNotifier for
cleanup. It walks its internal list of DMA mappings and unmaps them by
itself.
Future users of RAMBlockNotifier may not have an internal data structure
that records added RAMBlocks so they will need ->ram_block_removed()
callbacks.
This patch makes ram_block_notifier_remove() symmetric with respect to
callbacks. Now util/vfio-helpers.c needs to unmap remaining DMA mappings
after ram_block_notifier_remove() has been called. This is necessary
since users like block/nvme.c may create additional DMA mappings that do
not originate from the RAMBlockNotifier.
Reviewed-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
hw/core/numa.c | 17 +++++++++++++++++
util/vfio-helpers.c | 5 ++++-
2 files changed, 21 insertions(+), 1 deletion(-)
diff --git a/hw/core/numa.c b/hw/core/numa.c
index 26d8e5f616..31e6fe1caa 100644
--- a/hw/core/numa.c
+++ b/hw/core/numa.c
@@ -822,6 +822,19 @@ static int ram_block_notify_add_single(RAMBlock *rb, void *opaque)
return 0;
}
+static int ram_block_notify_remove_single(RAMBlock *rb, void *opaque)
+{
+ const ram_addr_t max_size = qemu_ram_get_max_length(rb);
+ const ram_addr_t size = qemu_ram_get_used_length(rb);
+ void *host = qemu_ram_get_host_addr(rb);
+ RAMBlockNotifier *notifier = opaque;
+
+ if (host) {
+ notifier->ram_block_removed(notifier, host, size, max_size);
+ }
+ return 0;
+}
+
void ram_block_notifier_add(RAMBlockNotifier *n)
{
QLIST_INSERT_HEAD(&ram_list.ramblock_notifiers, n, next);
@@ -835,6 +848,10 @@ void ram_block_notifier_add(RAMBlockNotifier *n)
void ram_block_notifier_remove(RAMBlockNotifier *n)
{
QLIST_REMOVE(n, next);
+
+ if (n->ram_block_removed) {
+ qemu_ram_foreach_block(ram_block_notify_remove_single, n);
+ }
}
void ram_block_notify_add(void *host, size_t size, size_t max_size)
diff --git a/util/vfio-helpers.c b/util/vfio-helpers.c
index 5ba01177bf..0d1520caac 100644
--- a/util/vfio-helpers.c
+++ b/util/vfio-helpers.c
@@ -847,10 +847,13 @@ void qemu_vfio_close(QEMUVFIOState *s)
if (!s) {
return;
}
+
+ ram_block_notifier_remove(&s->ram_notifier);
+
for (i = 0; i < s->nr_mappings; ++i) {
qemu_vfio_undo_mapping(s, &s->mappings[i], NULL);
}
- ram_block_notifier_remove(&s->ram_notifier);
+
g_free(s->usable_iova_ranges);
s->nb_iova_ranges = 0;
qemu_vfio_reset(s);
--
2.37.2
^ permalink raw reply related [flat|nested] 23+ messages in thread
* [RFC v4 03/11] block: pass size to bdrv_unregister_buf()
2022-08-22 22:23 [RFC v4 00/11] blkio: add libblkio BlockDriver Stefan Hajnoczi
2022-08-22 22:23 ` [RFC v4 01/11] blkio: add libblkio block driver Stefan Hajnoczi
2022-08-22 22:23 ` [RFC v4 02/11] numa: call ->ram_block_removed() in ram_block_notifer_remove() Stefan Hajnoczi
@ 2022-08-22 22:23 ` Stefan Hajnoczi
2022-08-22 22:23 ` [RFC v4 04/11] block: use BdrvRequestFlags type for supported flag fields Stefan Hajnoczi
` (8 subsequent siblings)
11 siblings, 0 replies; 23+ messages in thread
From: Stefan Hajnoczi @ 2022-08-22 22:23 UTC (permalink / raw)
To: qemu-devel
Cc: Paolo Bonzini, Denis V. Lunev, Peter Xu, Yanan Wang,
Marcel Apfelbaum, Richard W.M. Jones, qemu-block, John Snow,
integration, Vladimir Sementsov-Ogievskiy,
Vladimir Sementsov-Ogievskiy, David Hildenbrand, Laurent Vivier,
Markus Armbruster, Raphael Norwitz, Richard Henderson, Fam Zheng,
sgarzare, Alberto Faria, Kevin Wolf, Stefan Hajnoczi,
Wen Congyang, Eric Blake, Hanna Reitz,
Philippe Mathieu-Daudé,
Eduardo Habkost, Michael S. Tsirkin, Thomas Huth, Jeff Cody,
Xie Changlong
The only implementor of bdrv_register_buf() is block/nvme.c, where the
size is not needed when unregistering a buffer. This is because
util/vfio-helpers.c can look up mappings by address.
Future block drivers that implement bdrv_register_buf() may not be able
to do their job given only the buffer address. Add a size argument to
bdrv_unregister_buf().
Also document the assumptions about
bdrv_register_buf()/bdrv_unregister_buf() calls. The same <host, size>
values that were given to bdrv_register_buf() must be given to
bdrv_unregister_buf().
gcc 11.2.1 emits a spurious warning that img_bench()'s buf_size local
variable might be uninitialized, so it's necessary to silence the
compiler.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
include/block/block-global-state.h | 5 ++++-
include/block/block_int-common.h | 2 +-
include/sysemu/block-backend-global-state.h | 2 +-
block/block-backend.c | 4 ++--
block/io.c | 6 +++---
block/nvme.c | 2 +-
qemu-img.c | 4 ++--
7 files changed, 14 insertions(+), 11 deletions(-)
diff --git a/include/block/block-global-state.h b/include/block/block-global-state.h
index 21265e3966..7901f35863 100644
--- a/include/block/block-global-state.h
+++ b/include/block/block-global-state.h
@@ -243,9 +243,12 @@ void bdrv_del_child(BlockDriverState *parent, BdrvChild *child, Error **errp);
* Register/unregister a buffer for I/O. For example, VFIO drivers are
* interested to know the memory areas that would later be used for I/O, so
* that they can prepare IOMMU mapping etc., to get better performance.
+ *
+ * Buffers must not overlap and they must be unregistered with the same <host,
+ * size> values that they were registered with.
*/
void bdrv_register_buf(BlockDriverState *bs, void *host, size_t size);
-void bdrv_unregister_buf(BlockDriverState *bs, void *host);
+void bdrv_unregister_buf(BlockDriverState *bs, void *host, size_t size);
void bdrv_cancel_in_flight(BlockDriverState *bs);
diff --git a/include/block/block_int-common.h b/include/block/block_int-common.h
index 8947abab76..b7a7cbd3a5 100644
--- a/include/block/block_int-common.h
+++ b/include/block/block_int-common.h
@@ -435,7 +435,7 @@ struct BlockDriver {
* DMA mapping for hot buffers.
*/
void (*bdrv_register_buf)(BlockDriverState *bs, void *host, size_t size);
- void (*bdrv_unregister_buf)(BlockDriverState *bs, void *host);
+ void (*bdrv_unregister_buf)(BlockDriverState *bs, void *host, size_t size);
/*
* This field is modified only under the BQL, and is part of
diff --git a/include/sysemu/block-backend-global-state.h b/include/sysemu/block-backend-global-state.h
index 415f0c91d7..97f7dad2c3 100644
--- a/include/sysemu/block-backend-global-state.h
+++ b/include/sysemu/block-backend-global-state.h
@@ -107,7 +107,7 @@ void blk_io_limits_update_group(BlockBackend *blk, const char *group);
void blk_set_force_allow_inactivate(BlockBackend *blk);
void blk_register_buf(BlockBackend *blk, void *host, size_t size);
-void blk_unregister_buf(BlockBackend *blk, void *host);
+void blk_unregister_buf(BlockBackend *blk, void *host, size_t size);
const BdrvChild *blk_root(BlockBackend *blk);
diff --git a/block/block-backend.c b/block/block-backend.c
index d4a5df2ac2..99141f8f06 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -2551,10 +2551,10 @@ void blk_register_buf(BlockBackend *blk, void *host, size_t size)
bdrv_register_buf(blk_bs(blk), host, size);
}
-void blk_unregister_buf(BlockBackend *blk, void *host)
+void blk_unregister_buf(BlockBackend *blk, void *host, size_t size)
{
GLOBAL_STATE_CODE();
- bdrv_unregister_buf(blk_bs(blk), host);
+ bdrv_unregister_buf(blk_bs(blk), host, size);
}
int coroutine_fn blk_co_copy_range(BlockBackend *blk_in, int64_t off_in,
diff --git a/block/io.c b/block/io.c
index 0a8cbefe86..af85fa4bcc 100644
--- a/block/io.c
+++ b/block/io.c
@@ -3305,16 +3305,16 @@ void bdrv_register_buf(BlockDriverState *bs, void *host, size_t size)
}
}
-void bdrv_unregister_buf(BlockDriverState *bs, void *host)
+void bdrv_unregister_buf(BlockDriverState *bs, void *host, size_t size)
{
BdrvChild *child;
GLOBAL_STATE_CODE();
if (bs->drv && bs->drv->bdrv_unregister_buf) {
- bs->drv->bdrv_unregister_buf(bs, host);
+ bs->drv->bdrv_unregister_buf(bs, host, size);
}
QLIST_FOREACH(child, &bs->children, next) {
- bdrv_unregister_buf(child->bs, host);
+ bdrv_unregister_buf(child->bs, host, size);
}
}
diff --git a/block/nvme.c b/block/nvme.c
index 01fb28aa63..696502acea 100644
--- a/block/nvme.c
+++ b/block/nvme.c
@@ -1592,7 +1592,7 @@ static void nvme_register_buf(BlockDriverState *bs, void *host, size_t size)
}
}
-static void nvme_unregister_buf(BlockDriverState *bs, void *host)
+static void nvme_unregister_buf(BlockDriverState *bs, void *host, size_t size)
{
BDRVNVMeState *s = bs->opaque;
diff --git a/qemu-img.c b/qemu-img.c
index 7d4b33b3da..b8a8818ddb 100644
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -4368,7 +4368,7 @@ static int img_bench(int argc, char **argv)
struct timeval t1, t2;
int i;
bool force_share = false;
- size_t buf_size;
+ size_t buf_size = 0;
for (;;) {
static const struct option long_options[] = {
@@ -4590,7 +4590,7 @@ static int img_bench(int argc, char **argv)
out:
if (data.buf) {
- blk_unregister_buf(blk, data.buf);
+ blk_unregister_buf(blk, data.buf, buf_size);
}
qemu_vfree(data.buf);
blk_unref(blk);
--
2.37.2
^ permalink raw reply related [flat|nested] 23+ messages in thread
* [RFC v4 04/11] block: use BdrvRequestFlags type for supported flag fields
2022-08-22 22:23 [RFC v4 00/11] blkio: add libblkio BlockDriver Stefan Hajnoczi
` (2 preceding siblings ...)
2022-08-22 22:23 ` [RFC v4 03/11] block: pass size to bdrv_unregister_buf() Stefan Hajnoczi
@ 2022-08-22 22:23 ` Stefan Hajnoczi
2022-08-22 22:23 ` [RFC v4 05/11] block: add BDRV_REQ_REGISTERED_BUF request flag Stefan Hajnoczi
` (7 subsequent siblings)
11 siblings, 0 replies; 23+ messages in thread
From: Stefan Hajnoczi @ 2022-08-22 22:23 UTC (permalink / raw)
To: qemu-devel
Cc: Paolo Bonzini, Denis V. Lunev, Peter Xu, Yanan Wang,
Marcel Apfelbaum, Richard W.M. Jones, qemu-block, John Snow,
integration, Vladimir Sementsov-Ogievskiy,
Vladimir Sementsov-Ogievskiy, David Hildenbrand, Laurent Vivier,
Markus Armbruster, Raphael Norwitz, Richard Henderson, Fam Zheng,
sgarzare, Alberto Faria, Kevin Wolf, Stefan Hajnoczi,
Wen Congyang, Eric Blake, Hanna Reitz,
Philippe Mathieu-Daudé,
Eduardo Habkost, Michael S. Tsirkin, Thomas Huth, Jeff Cody,
Xie Changlong
Use the enum type so GDB displays the enum members instead of printing a
numeric constant.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
include/block/block_int-common.h | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/include/block/block_int-common.h b/include/block/block_int-common.h
index b7a7cbd3a5..19798d0e77 100644
--- a/include/block/block_int-common.h
+++ b/include/block/block_int-common.h
@@ -1051,7 +1051,7 @@ struct BlockDriverState {
/*
* Flags honored during pread
*/
- unsigned int supported_read_flags;
+ BdrvRequestFlags supported_read_flags;
/*
* Flags honored during pwrite (so far: BDRV_REQ_FUA,
* BDRV_REQ_WRITE_UNCHANGED).
@@ -1069,12 +1069,12 @@ struct BlockDriverState {
* flag), or they have to explicitly take the WRITE permission for
* their children.
*/
- unsigned int supported_write_flags;
+ BdrvRequestFlags supported_write_flags;
/*
* Flags honored during pwrite_zeroes (so far: BDRV_REQ_FUA,
* BDRV_REQ_MAY_UNMAP, BDRV_REQ_WRITE_UNCHANGED)
*/
- unsigned int supported_zero_flags;
+ BdrvRequestFlags supported_zero_flags;
/*
* Flags honoured during truncate (so far: BDRV_REQ_ZERO_WRITE).
*
@@ -1082,7 +1082,7 @@ struct BlockDriverState {
* that any added space reads as all zeros. If this can't be guaranteed,
* the operation must fail.
*/
- unsigned int supported_truncate_flags;
+ BdrvRequestFlags supported_truncate_flags;
/* the following member gives a name to every node on the bs graph. */
char node_name[32];
--
2.37.2
^ permalink raw reply related [flat|nested] 23+ messages in thread
* [RFC v4 05/11] block: add BDRV_REQ_REGISTERED_BUF request flag
2022-08-22 22:23 [RFC v4 00/11] blkio: add libblkio BlockDriver Stefan Hajnoczi
` (3 preceding siblings ...)
2022-08-22 22:23 ` [RFC v4 04/11] block: use BdrvRequestFlags type for supported flag fields Stefan Hajnoczi
@ 2022-08-22 22:23 ` Stefan Hajnoczi
2022-08-22 22:23 ` [RFC v4 06/11] block: return errors from bdrv_register_buf() Stefan Hajnoczi
` (6 subsequent siblings)
11 siblings, 0 replies; 23+ messages in thread
From: Stefan Hajnoczi @ 2022-08-22 22:23 UTC (permalink / raw)
To: qemu-devel
Cc: Paolo Bonzini, Denis V. Lunev, Peter Xu, Yanan Wang,
Marcel Apfelbaum, Richard W.M. Jones, qemu-block, John Snow,
integration, Vladimir Sementsov-Ogievskiy,
Vladimir Sementsov-Ogievskiy, David Hildenbrand, Laurent Vivier,
Markus Armbruster, Raphael Norwitz, Richard Henderson, Fam Zheng,
sgarzare, Alberto Faria, Kevin Wolf, Stefan Hajnoczi,
Wen Congyang, Eric Blake, Hanna Reitz,
Philippe Mathieu-Daudé,
Eduardo Habkost, Michael S. Tsirkin, Thomas Huth, Jeff Cody,
Xie Changlong
Block drivers may optimize I/O requests accessing buffers previously
registered with bdrv_register_buf(). Checking whether all elements of a
request's QEMUIOVector are within previously registered buffers is
expensive, so we need a hint from the user to avoid costly checks.
Add a BDRV_REQ_REGISTERED_BUF request flag to indicate that all
QEMUIOVector elements in an I/O request are known to be within
previously registered buffers.
Always pass the flag through to driver read/write functions. There is
little harm in passing the flag to a driver that does not use it.
Passing the flag to drivers avoids changes across many block drivers.
Filter drivers would need to explicitly support the flag and pass
through to their children when the children support it. That's a lot of
code changes and it's hard to remember to do that everywhere, leading to
silent reduced performance when the flag is accidentally dropped.
The only problematic scenario with the approach in this patch is when a
driver passes the flag through to internal I/O requests that don't use
the same I/O buffer. In that case the hint may be set when it should
actually be clear. This is a rare case though so the risk is low.
Some drivers have assert(!flags), which no longer works when
BDRV_REQ_REGISTERED_BUF is passed in. These assertions aren't very
useful anyway since the functions are called almost exclusively by
bdrv_driver_preadv/pwritev() so if we get flags handling right there
then the assertion is not needed.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
include/block/block-common.h | 9 ++++++
block.c | 14 +++++++++
block/blkverify.c | 4 +--
block/crypto.c | 4 +--
block/file-posix.c | 1 -
block/gluster.c | 1 -
block/io.c | 61 ++++++++++++++++++++++--------------
block/mirror.c | 2 ++
block/nbd.c | 1 -
block/parallels.c | 1 -
block/qcow.c | 2 --
block/qed.c | 1 -
block/raw-format.c | 2 ++
block/replication.c | 1 -
block/ssh.c | 1 -
block/vhdx.c | 1 -
16 files changed, 69 insertions(+), 37 deletions(-)
diff --git a/include/block/block-common.h b/include/block/block-common.h
index fdb7306e78..061606e867 100644
--- a/include/block/block-common.h
+++ b/include/block/block-common.h
@@ -80,6 +80,15 @@ typedef enum {
*/
BDRV_REQ_MAY_UNMAP = 0x4,
+ /*
+ * An optimization hint when all QEMUIOVector elements are within
+ * previously registered bdrv_register_buf() memory ranges.
+ *
+ * Code that replaces the user's QEMUIOVector elements with bounce buffers
+ * must take care to clear this flag.
+ */
+ BDRV_REQ_REGISTERED_BUF = 0x8,
+
BDRV_REQ_FUA = 0x10,
BDRV_REQ_WRITE_COMPRESSED = 0x20,
diff --git a/block.c b/block.c
index bc85f46eed..70abbf774e 100644
--- a/block.c
+++ b/block.c
@@ -1640,6 +1640,20 @@ static int bdrv_open_driver(BlockDriverState *bs, BlockDriver *drv,
goto open_failed;
}
+ assert(!(bs->supported_read_flags & ~BDRV_REQ_MASK));
+ assert(!(bs->supported_write_flags & ~BDRV_REQ_MASK));
+
+ /*
+ * Always allow the BDRV_REQ_REGISTERED_BUF optimization hint. This saves
+ * drivers that pass read/write requests through to a child the trouble of
+ * declaring support explicitly.
+ *
+ * Drivers must not propagate this flag accidentally when they initiate I/O
+ * to a bounce buffer. That case should be rare though.
+ */
+ bs->supported_read_flags |= BDRV_REQ_REGISTERED_BUF;
+ bs->supported_write_flags |= BDRV_REQ_REGISTERED_BUF;
+
ret = refresh_total_sectors(bs, bs->total_sectors);
if (ret < 0) {
error_setg_errno(errp, -ret, "Could not refresh total sector count");
diff --git a/block/blkverify.c b/block/blkverify.c
index e4a37af3b2..d624f4fd05 100644
--- a/block/blkverify.c
+++ b/block/blkverify.c
@@ -235,8 +235,8 @@ blkverify_co_preadv(BlockDriverState *bs, int64_t offset, int64_t bytes,
qemu_iovec_init(&raw_qiov, qiov->niov);
qemu_iovec_clone(&raw_qiov, qiov, buf);
- ret = blkverify_co_prwv(bs, &r, offset, bytes, qiov, &raw_qiov, flags,
- false);
+ ret = blkverify_co_prwv(bs, &r, offset, bytes, qiov, &raw_qiov,
+ flags & ~BDRV_REQ_REGISTERED_BUF, false);
cmp_offset = qemu_iovec_compare(qiov, &raw_qiov);
if (cmp_offset != -1) {
diff --git a/block/crypto.c b/block/crypto.c
index 7a57774b76..c7365598a7 100644
--- a/block/crypto.c
+++ b/block/crypto.c
@@ -410,7 +410,6 @@ block_crypto_co_preadv(BlockDriverState *bs, int64_t offset, int64_t bytes,
uint64_t sector_size = qcrypto_block_get_sector_size(crypto->block);
uint64_t payload_offset = qcrypto_block_get_payload_offset(crypto->block);
- assert(!flags);
assert(payload_offset < INT64_MAX);
assert(QEMU_IS_ALIGNED(offset, sector_size));
assert(QEMU_IS_ALIGNED(bytes, sector_size));
@@ -473,7 +472,8 @@ block_crypto_co_pwritev(BlockDriverState *bs, int64_t offset, int64_t bytes,
uint64_t sector_size = qcrypto_block_get_sector_size(crypto->block);
uint64_t payload_offset = qcrypto_block_get_payload_offset(crypto->block);
- assert(!(flags & ~BDRV_REQ_FUA));
+ flags &= ~BDRV_REQ_REGISTERED_BUF;
+
assert(payload_offset < INT64_MAX);
assert(QEMU_IS_ALIGNED(offset, sector_size));
assert(QEMU_IS_ALIGNED(bytes, sector_size));
diff --git a/block/file-posix.c b/block/file-posix.c
index 48cd096624..51fd57137d 100644
--- a/block/file-posix.c
+++ b/block/file-posix.c
@@ -2120,7 +2120,6 @@ static int coroutine_fn raw_co_pwritev(BlockDriverState *bs, int64_t offset,
int64_t bytes, QEMUIOVector *qiov,
BdrvRequestFlags flags)
{
- assert(flags == 0);
return raw_co_prw(bs, offset, bytes, qiov, QEMU_AIO_WRITE);
}
diff --git a/block/gluster.c b/block/gluster.c
index b60213ab80..3894422e23 100644
--- a/block/gluster.c
+++ b/block/gluster.c
@@ -1236,7 +1236,6 @@ static coroutine_fn int qemu_gluster_co_writev(BlockDriverState *bs,
QEMUIOVector *qiov,
int flags)
{
- assert(!flags);
return qemu_gluster_co_rw(bs, sector_num, nb_sectors, qiov, 1);
}
diff --git a/block/io.c b/block/io.c
index af85fa4bcc..de04594299 100644
--- a/block/io.c
+++ b/block/io.c
@@ -1139,8 +1139,7 @@ static int coroutine_fn bdrv_driver_preadv(BlockDriverState *bs,
int ret;
bdrv_check_qiov_request(offset, bytes, qiov, qiov_offset, &error_abort);
- assert(!(flags & ~BDRV_REQ_MASK));
- assert(!(flags & BDRV_REQ_NO_FALLBACK));
+ assert(!(flags & ~bs->supported_read_flags));
if (!drv) {
return -ENOMEDIUM;
@@ -1204,23 +1203,29 @@ static int coroutine_fn bdrv_driver_pwritev(BlockDriverState *bs,
BdrvRequestFlags flags)
{
BlockDriver *drv = bs->drv;
+ bool emulate_fua = false;
int64_t sector_num;
unsigned int nb_sectors;
QEMUIOVector local_qiov;
int ret;
bdrv_check_qiov_request(offset, bytes, qiov, qiov_offset, &error_abort);
- assert(!(flags & ~BDRV_REQ_MASK));
- assert(!(flags & BDRV_REQ_NO_FALLBACK));
if (!drv) {
return -ENOMEDIUM;
}
+ if ((flags & BDRV_REQ_FUA) &&
+ (~bs->supported_write_flags & BDRV_REQ_FUA)) {
+ flags &= ~BDRV_REQ_FUA;
+ emulate_fua = true;
+ }
+
+ flags &= bs->supported_write_flags;
+
if (drv->bdrv_co_pwritev_part) {
ret = drv->bdrv_co_pwritev_part(bs, offset, bytes, qiov, qiov_offset,
- flags & bs->supported_write_flags);
- flags &= ~bs->supported_write_flags;
+ flags);
goto emulate_flags;
}
@@ -1230,9 +1235,7 @@ static int coroutine_fn bdrv_driver_pwritev(BlockDriverState *bs,
}
if (drv->bdrv_co_pwritev) {
- ret = drv->bdrv_co_pwritev(bs, offset, bytes, qiov,
- flags & bs->supported_write_flags);
- flags &= ~bs->supported_write_flags;
+ ret = drv->bdrv_co_pwritev(bs, offset, bytes, qiov, flags);
goto emulate_flags;
}
@@ -1242,10 +1245,8 @@ static int coroutine_fn bdrv_driver_pwritev(BlockDriverState *bs,
.coroutine = qemu_coroutine_self(),
};
- acb = drv->bdrv_aio_pwritev(bs, offset, bytes, qiov,
- flags & bs->supported_write_flags,
+ acb = drv->bdrv_aio_pwritev(bs, offset, bytes, qiov, flags,
bdrv_co_io_em_complete, &co);
- flags &= ~bs->supported_write_flags;
if (acb == NULL) {
ret = -EIO;
} else {
@@ -1263,12 +1264,10 @@ static int coroutine_fn bdrv_driver_pwritev(BlockDriverState *bs,
assert(bytes <= BDRV_REQUEST_MAX_BYTES);
assert(drv->bdrv_co_writev);
- ret = drv->bdrv_co_writev(bs, sector_num, nb_sectors, qiov,
- flags & bs->supported_write_flags);
- flags &= ~bs->supported_write_flags;
+ ret = drv->bdrv_co_writev(bs, sector_num, nb_sectors, qiov, flags);
emulate_flags:
- if (ret == 0 && (flags & BDRV_REQ_FUA)) {
+ if (ret == 0 && emulate_fua) {
ret = bdrv_co_flush(bs);
}
@@ -1496,11 +1495,14 @@ static int coroutine_fn bdrv_aligned_preadv(BdrvChild *child,
max_transfer = QEMU_ALIGN_DOWN(MIN_NON_ZERO(bs->bl.max_transfer, INT_MAX),
align);
- /* TODO: We would need a per-BDS .supported_read_flags and
+ /*
+ * TODO: We would need a per-BDS .supported_read_flags and
* potential fallback support, if we ever implement any read flags
* to pass through to drivers. For now, there aren't any
- * passthrough flags. */
- assert(!(flags & ~(BDRV_REQ_COPY_ON_READ | BDRV_REQ_PREFETCH)));
+ * passthrough flags except the BDRV_REQ_REGISTERED_BUF optimization hint.
+ */
+ assert(!(flags & ~(BDRV_REQ_COPY_ON_READ | BDRV_REQ_PREFETCH |
+ BDRV_REQ_REGISTERED_BUF)));
/* Handle Copy on Read and associated serialisation */
if (flags & BDRV_REQ_COPY_ON_READ) {
@@ -1541,7 +1543,7 @@ static int coroutine_fn bdrv_aligned_preadv(BdrvChild *child,
goto out;
}
- assert(!(flags & ~bs->supported_read_flags));
+ assert(!(flags & ~(bs->supported_read_flags | BDRV_REQ_REGISTERED_BUF)));
max_bytes = ROUND_UP(MAX(0, total_bytes - offset), align);
if (bytes <= max_bytes && bytes <= max_transfer) {
@@ -1730,7 +1732,8 @@ static void bdrv_padding_destroy(BdrvRequestPadding *pad)
static int bdrv_pad_request(BlockDriverState *bs,
QEMUIOVector **qiov, size_t *qiov_offset,
int64_t *offset, int64_t *bytes,
- BdrvRequestPadding *pad, bool *padded)
+ BdrvRequestPadding *pad, bool *padded,
+ BdrvRequestFlags *flags)
{
int ret;
@@ -1758,6 +1761,10 @@ static int bdrv_pad_request(BlockDriverState *bs,
if (padded) {
*padded = true;
}
+ if (flags) {
+ /* Can't use optimization hint with bounce buffer */
+ *flags &= ~BDRV_REQ_REGISTERED_BUF;
+ }
return 0;
}
@@ -1812,7 +1819,7 @@ int coroutine_fn bdrv_co_preadv_part(BdrvChild *child,
}
ret = bdrv_pad_request(bs, &qiov, &qiov_offset, &offset, &bytes, &pad,
- NULL);
+ NULL, &flags);
if (ret < 0) {
goto fail;
}
@@ -1857,6 +1864,11 @@ static int coroutine_fn bdrv_co_do_pwrite_zeroes(BlockDriverState *bs,
return -ENOTSUP;
}
+ /* By definition there is no user buffer so this flag doesn't make sense */
+ if (flags & BDRV_REQ_REGISTERED_BUF) {
+ return -EINVAL;
+ }
+
/* Invalidate the cached block-status data range if this write overlaps */
bdrv_bsc_invalidate_range(bs, offset, bytes);
@@ -2142,6 +2154,9 @@ static int coroutine_fn bdrv_co_do_zero_pwritev(BdrvChild *child,
bool padding;
BdrvRequestPadding pad;
+ /* This flag doesn't make sense for padding or zero writes */
+ flags &= ~BDRV_REQ_REGISTERED_BUF;
+
padding = bdrv_init_padding(bs, offset, bytes, &pad);
if (padding) {
assert(!(flags & BDRV_REQ_NO_WAIT));
@@ -2259,7 +2274,7 @@ int coroutine_fn bdrv_co_pwritev_part(BdrvChild *child,
* alignment only if there is no ZERO flag.
*/
ret = bdrv_pad_request(bs, &qiov, &qiov_offset, &offset, &bytes, &pad,
- &padded);
+ &padded, &flags);
if (ret < 0) {
return ret;
}
diff --git a/block/mirror.c b/block/mirror.c
index 3c4ab1159d..8d3fc3f19b 100644
--- a/block/mirror.c
+++ b/block/mirror.c
@@ -1477,6 +1477,8 @@ static int coroutine_fn bdrv_mirror_top_pwritev(BlockDriverState *bs,
qemu_iovec_init(&bounce_qiov, 1);
qemu_iovec_add(&bounce_qiov, bounce_buf, bytes);
qiov = &bounce_qiov;
+
+ flags &= ~BDRV_REQ_REGISTERED_BUF;
}
ret = bdrv_mirror_top_do_write(bs, MIRROR_METHOD_COPY, offset, bytes, qiov,
diff --git a/block/nbd.c b/block/nbd.c
index 97683cce27..ce2956e083 100644
--- a/block/nbd.c
+++ b/block/nbd.c
@@ -1221,7 +1221,6 @@ static int coroutine_fn nbd_client_co_preadv(BlockDriverState *bs, int64_t offse
};
assert(bytes <= NBD_MAX_BUFFER_SIZE);
- assert(!flags);
if (!bytes) {
return 0;
diff --git a/block/parallels.c b/block/parallels.c
index a229c06f25..7c04c6a135 100644
--- a/block/parallels.c
+++ b/block/parallels.c
@@ -328,7 +328,6 @@ static coroutine_fn int parallels_co_writev(BlockDriverState *bs,
QEMUIOVector hd_qiov;
int ret = 0;
- assert(!flags);
qemu_iovec_init(&hd_qiov, qiov->niov);
while (nb_sectors > 0) {
diff --git a/block/qcow.c b/block/qcow.c
index 311aaa8705..e9180c7b61 100644
--- a/block/qcow.c
+++ b/block/qcow.c
@@ -628,7 +628,6 @@ static coroutine_fn int qcow_co_preadv(BlockDriverState *bs, int64_t offset,
uint8_t *buf;
void *orig_buf;
- assert(!flags);
if (qiov->niov > 1) {
buf = orig_buf = qemu_try_blockalign(bs, qiov->size);
if (buf == NULL) {
@@ -725,7 +724,6 @@ static coroutine_fn int qcow_co_pwritev(BlockDriverState *bs, int64_t offset,
uint8_t *buf;
void *orig_buf;
- assert(!flags);
s->cluster_cache_offset = -1; /* disable compressed cache */
/* We must always copy the iov when encrypting, so we
diff --git a/block/qed.c b/block/qed.c
index 40943e679b..32429682a4 100644
--- a/block/qed.c
+++ b/block/qed.c
@@ -1388,7 +1388,6 @@ static int coroutine_fn bdrv_qed_co_writev(BlockDriverState *bs,
int64_t sector_num, int nb_sectors,
QEMUIOVector *qiov, int flags)
{
- assert(!flags);
return qed_co_request(bs, sector_num, qiov, nb_sectors, QED_AIOCB_WRITE);
}
diff --git a/block/raw-format.c b/block/raw-format.c
index 69fd650eaf..9bae3dd7f2 100644
--- a/block/raw-format.c
+++ b/block/raw-format.c
@@ -258,6 +258,8 @@ static int coroutine_fn raw_co_pwritev(BlockDriverState *bs, int64_t offset,
qemu_iovec_add(&local_qiov, buf, 512);
qemu_iovec_concat(&local_qiov, qiov, 512, qiov->size - 512);
qiov = &local_qiov;
+
+ flags &= ~BDRV_REQ_REGISTERED_BUF;
}
ret = raw_adjust_offset(bs, &offset, bytes, true);
diff --git a/block/replication.c b/block/replication.c
index 55c8f894aa..942f88b205 100644
--- a/block/replication.c
+++ b/block/replication.c
@@ -260,7 +260,6 @@ static coroutine_fn int replication_co_writev(BlockDriverState *bs,
int ret;
int64_t n;
- assert(!flags);
ret = replication_get_io_status(s);
if (ret < 0) {
goto out;
diff --git a/block/ssh.c b/block/ssh.c
index a2dc646536..a3cddc392c 100644
--- a/block/ssh.c
+++ b/block/ssh.c
@@ -1196,7 +1196,6 @@ static coroutine_fn int ssh_co_writev(BlockDriverState *bs,
BDRVSSHState *s = bs->opaque;
int ret;
- assert(!flags);
qemu_co_mutex_lock(&s->lock);
ret = ssh_write(s, bs, sector_num * BDRV_SECTOR_SIZE,
nb_sectors * BDRV_SECTOR_SIZE, qiov);
diff --git a/block/vhdx.c b/block/vhdx.c
index e10e78ebfd..e2344ee0b7 100644
--- a/block/vhdx.c
+++ b/block/vhdx.c
@@ -1342,7 +1342,6 @@ static coroutine_fn int vhdx_co_writev(BlockDriverState *bs, int64_t sector_num,
uint64_t bat_prior_offset = 0;
bool bat_update = false;
- assert(!flags);
qemu_iovec_init(&hd_qiov, qiov->niov);
qemu_co_mutex_lock(&s->lock);
--
2.37.2
^ permalink raw reply related [flat|nested] 23+ messages in thread
* [RFC v4 06/11] block: return errors from bdrv_register_buf()
2022-08-22 22:23 [RFC v4 00/11] blkio: add libblkio BlockDriver Stefan Hajnoczi
` (4 preceding siblings ...)
2022-08-22 22:23 ` [RFC v4 05/11] block: add BDRV_REQ_REGISTERED_BUF request flag Stefan Hajnoczi
@ 2022-08-22 22:23 ` Stefan Hajnoczi
2022-08-22 22:23 ` [RFC v4 07/11] block: add BlockRAMRegistrar Stefan Hajnoczi
` (5 subsequent siblings)
11 siblings, 0 replies; 23+ messages in thread
From: Stefan Hajnoczi @ 2022-08-22 22:23 UTC (permalink / raw)
To: qemu-devel
Cc: Paolo Bonzini, Denis V. Lunev, Peter Xu, Yanan Wang,
Marcel Apfelbaum, Richard W.M. Jones, qemu-block, John Snow,
integration, Vladimir Sementsov-Ogievskiy,
Vladimir Sementsov-Ogievskiy, David Hildenbrand, Laurent Vivier,
Markus Armbruster, Raphael Norwitz, Richard Henderson, Fam Zheng,
sgarzare, Alberto Faria, Kevin Wolf, Stefan Hajnoczi,
Wen Congyang, Eric Blake, Hanna Reitz,
Philippe Mathieu-Daudé,
Eduardo Habkost, Michael S. Tsirkin, Thomas Huth, Jeff Cody,
Xie Changlong
Registering an I/O buffer is only a performance optimization hint but it
is still necessary to return errors when it fails.
Later patches will need to detect errors when registering buffers but an
immediate advantage is that error_report() calls are no longer needed in
block driver .bdrv_register_buf() functions.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
include/block/block-global-state.h | 5 ++-
include/block/block_int-common.h | 5 ++-
include/sysemu/block-backend-global-state.h | 2 +-
block/block-backend.c | 4 +--
block/io.c | 34 +++++++++++++++++++--
block/nvme.c | 18 +++++------
qemu-img.c | 2 +-
7 files changed, 52 insertions(+), 18 deletions(-)
diff --git a/include/block/block-global-state.h b/include/block/block-global-state.h
index 7901f35863..eba4ed23b4 100644
--- a/include/block/block-global-state.h
+++ b/include/block/block-global-state.h
@@ -246,8 +246,11 @@ void bdrv_del_child(BlockDriverState *parent, BdrvChild *child, Error **errp);
*
* Buffers must not overlap and they must be unregistered with the same <host,
* size> values that they were registered with.
+ *
+ * Returns: true on success, false on failure
*/
-void bdrv_register_buf(BlockDriverState *bs, void *host, size_t size);
+bool bdrv_register_buf(BlockDriverState *bs, void *host, size_t size,
+ Error **errp);
void bdrv_unregister_buf(BlockDriverState *bs, void *host, size_t size);
void bdrv_cancel_in_flight(BlockDriverState *bs);
diff --git a/include/block/block_int-common.h b/include/block/block_int-common.h
index 19798d0e77..9c569be162 100644
--- a/include/block/block_int-common.h
+++ b/include/block/block_int-common.h
@@ -433,8 +433,11 @@ struct BlockDriver {
* that it can do IOMMU mapping with VFIO etc., in order to get better
* performance. In the case of VFIO drivers, this callback is used to do
* DMA mapping for hot buffers.
+ *
+ * Returns: true on success, false on failure
*/
- void (*bdrv_register_buf)(BlockDriverState *bs, void *host, size_t size);
+ bool (*bdrv_register_buf)(BlockDriverState *bs, void *host, size_t size,
+ Error **errp);
void (*bdrv_unregister_buf)(BlockDriverState *bs, void *host, size_t size);
/*
diff --git a/include/sysemu/block-backend-global-state.h b/include/sysemu/block-backend-global-state.h
index 97f7dad2c3..6858e39cb6 100644
--- a/include/sysemu/block-backend-global-state.h
+++ b/include/sysemu/block-backend-global-state.h
@@ -106,7 +106,7 @@ void blk_io_limits_enable(BlockBackend *blk, const char *group);
void blk_io_limits_update_group(BlockBackend *blk, const char *group);
void blk_set_force_allow_inactivate(BlockBackend *blk);
-void blk_register_buf(BlockBackend *blk, void *host, size_t size);
+bool blk_register_buf(BlockBackend *blk, void *host, size_t size, Error **errp);
void blk_unregister_buf(BlockBackend *blk, void *host, size_t size);
const BdrvChild *blk_root(BlockBackend *blk);
diff --git a/block/block-backend.c b/block/block-backend.c
index 99141f8f06..34399d3b7b 100644
--- a/block/block-backend.c
+++ b/block/block-backend.c
@@ -2545,10 +2545,10 @@ static void blk_root_drained_end(BdrvChild *child, int *drained_end_counter)
}
}
-void blk_register_buf(BlockBackend *blk, void *host, size_t size)
+bool blk_register_buf(BlockBackend *blk, void *host, size_t size, Error **errp)
{
GLOBAL_STATE_CODE();
- bdrv_register_buf(blk_bs(blk), host, size);
+ return bdrv_register_buf(blk_bs(blk), host, size, errp);
}
void blk_unregister_buf(BlockBackend *blk, void *host, size_t size)
diff --git a/block/io.c b/block/io.c
index de04594299..1c3392c7f6 100644
--- a/block/io.c
+++ b/block/io.c
@@ -3307,17 +3307,45 @@ void bdrv_io_unplug(BlockDriverState *bs)
}
}
-void bdrv_register_buf(BlockDriverState *bs, void *host, size_t size)
+/* Helper that undoes bdrv_register_buf() when it fails partway through */
+static void bdrv_register_buf_rollback(BlockDriverState *bs,
+ void *host,
+ size_t size,
+ BdrvChild *final_child)
+{
+ BdrvChild *child;
+
+ QLIST_FOREACH(child, &bs->children, next) {
+ if (child == final_child) {
+ break;
+ }
+
+ bdrv_unregister_buf(child->bs, host, size);
+ }
+
+ if (bs->drv && bs->drv->bdrv_unregister_buf) {
+ bs->drv->bdrv_unregister_buf(bs, host, size);
+ }
+}
+
+bool bdrv_register_buf(BlockDriverState *bs, void *host, size_t size,
+ Error **errp)
{
BdrvChild *child;
GLOBAL_STATE_CODE();
if (bs->drv && bs->drv->bdrv_register_buf) {
- bs->drv->bdrv_register_buf(bs, host, size);
+ if (!bs->drv->bdrv_register_buf(bs, host, size, errp)) {
+ return false;
+ }
}
QLIST_FOREACH(child, &bs->children, next) {
- bdrv_register_buf(child->bs, host, size);
+ if (!bdrv_register_buf(child->bs, host, size, errp)) {
+ bdrv_register_buf_rollback(bs, host, size, child);
+ return false;
+ }
}
+ return true;
}
void bdrv_unregister_buf(BlockDriverState *bs, void *host, size_t size)
diff --git a/block/nvme.c b/block/nvme.c
index 696502acea..1e76fe21d3 100644
--- a/block/nvme.c
+++ b/block/nvme.c
@@ -1577,19 +1577,19 @@ static void nvme_aio_unplug(BlockDriverState *bs)
}
}
-static void nvme_register_buf(BlockDriverState *bs, void *host, size_t size)
+static bool nvme_register_buf(BlockDriverState *bs, void *host, size_t size,
+ Error **errp)
{
int ret;
- Error *local_err = NULL;
BDRVNVMeState *s = bs->opaque;
- ret = qemu_vfio_dma_map(s->vfio, host, size, false, NULL, &local_err);
- if (ret) {
- /* FIXME: we may run out of IOVA addresses after repeated
- * bdrv_register_buf/bdrv_unregister_buf, because nvme_vfio_dma_unmap
- * doesn't reclaim addresses for fixed mappings. */
- error_reportf_err(local_err, "nvme_register_buf failed: ");
- }
+ /*
+ * FIXME: we may run out of IOVA addresses after repeated
+ * bdrv_register_buf/bdrv_unregister_buf, because nvme_vfio_dma_unmap
+ * doesn't reclaim addresses for fixed mappings.
+ */
+ ret = qemu_vfio_dma_map(s->vfio, host, size, false, NULL, errp);
+ return ret == 0;
}
static void nvme_unregister_buf(BlockDriverState *bs, void *host, size_t size)
diff --git a/qemu-img.c b/qemu-img.c
index b8a8818ddb..3f2927f5b4 100644
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -4567,7 +4567,7 @@ static int img_bench(int argc, char **argv)
data.buf = blk_blockalign(blk, buf_size);
memset(data.buf, pattern, data.nrreq * data.bufsize);
- blk_register_buf(blk, data.buf, buf_size);
+ blk_register_buf(blk, data.buf, buf_size, &error_fatal);
data.qiov = g_new(QEMUIOVector, data.nrreq);
for (i = 0; i < data.nrreq; i++) {
--
2.37.2
^ permalink raw reply related [flat|nested] 23+ messages in thread
* [RFC v4 07/11] block: add BlockRAMRegistrar
2022-08-22 22:23 [RFC v4 00/11] blkio: add libblkio BlockDriver Stefan Hajnoczi
` (5 preceding siblings ...)
2022-08-22 22:23 ` [RFC v4 06/11] block: return errors from bdrv_register_buf() Stefan Hajnoczi
@ 2022-08-22 22:23 ` Stefan Hajnoczi
2022-08-22 22:23 ` [RFC v4 08/11] exec/cpu-common: add qemu_ram_get_fd() Stefan Hajnoczi
` (4 subsequent siblings)
11 siblings, 0 replies; 23+ messages in thread
From: Stefan Hajnoczi @ 2022-08-22 22:23 UTC (permalink / raw)
To: qemu-devel
Cc: Paolo Bonzini, Denis V. Lunev, Peter Xu, Yanan Wang,
Marcel Apfelbaum, Richard W.M. Jones, qemu-block, John Snow,
integration, Vladimir Sementsov-Ogievskiy,
Vladimir Sementsov-Ogievskiy, David Hildenbrand, Laurent Vivier,
Markus Armbruster, Raphael Norwitz, Richard Henderson, Fam Zheng,
sgarzare, Alberto Faria, Kevin Wolf, Stefan Hajnoczi,
Wen Congyang, Eric Blake, Hanna Reitz,
Philippe Mathieu-Daudé,
Eduardo Habkost, Michael S. Tsirkin, Thomas Huth, Jeff Cody,
Xie Changlong
Emulated devices and other BlockBackend users wishing to take advantage
of blk_register_buf() all have the same repetitive job: register
RAMBlocks with the BlockBackend using RAMBlockNotifier.
Add a BlockRAMRegistrar API to do this. A later commit will use this
from hw/block/virtio-blk.c.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
MAINTAINERS | 1 +
include/sysemu/block-ram-registrar.h | 37 +++++++++++++++++++
block/block-ram-registrar.c | 54 ++++++++++++++++++++++++++++
block/meson.build | 1 +
4 files changed, 93 insertions(+)
create mode 100644 include/sysemu/block-ram-registrar.h
create mode 100644 block/block-ram-registrar.c
diff --git a/MAINTAINERS b/MAINTAINERS
index f8ccd5954c..a3f74ab42a 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -2491,6 +2491,7 @@ F: block*
F: block/
F: hw/block/
F: include/block/
+F: include/sysemu/block-*.h
F: qemu-img*
F: docs/tools/qemu-img.rst
F: qemu-io*
diff --git a/include/sysemu/block-ram-registrar.h b/include/sysemu/block-ram-registrar.h
new file mode 100644
index 0000000000..d8b2f7942b
--- /dev/null
+++ b/include/sysemu/block-ram-registrar.h
@@ -0,0 +1,37 @@
+/*
+ * BlockBackend RAM Registrar
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+#ifndef BLOCK_RAM_REGISTRAR_H
+#define BLOCK_RAM_REGISTRAR_H
+
+#include "exec/ramlist.h"
+
+/**
+ * struct BlockRAMRegistrar:
+ *
+ * Keeps RAMBlock memory registered with a BlockBackend using
+ * blk_register_buf() including hotplugged memory.
+ *
+ * Emulated devices or other BlockBackend users initialize a BlockRAMRegistrar
+ * with blk_ram_registrar_init() before submitting I/O requests with the
+ * BDRV_REQ_REGISTERED_BUF flag set.
+ */
+typedef struct {
+ BlockBackend *blk;
+ RAMBlockNotifier notifier;
+ bool ok;
+} BlockRAMRegistrar;
+
+void blk_ram_registrar_init(BlockRAMRegistrar *r, BlockBackend *blk);
+void blk_ram_registrar_destroy(BlockRAMRegistrar *r);
+
+/* Have all RAMBlocks been registered successfully? */
+static inline bool blk_ram_registrar_ok(BlockRAMRegistrar *r)
+{
+ return r->ok;
+}
+
+#endif /* BLOCK_RAM_REGISTRAR_H */
diff --git a/block/block-ram-registrar.c b/block/block-ram-registrar.c
new file mode 100644
index 0000000000..32935006c1
--- /dev/null
+++ b/block/block-ram-registrar.c
@@ -0,0 +1,54 @@
+/*
+ * BlockBackend RAM Registrar
+ *
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ */
+
+#include "qemu/osdep.h"
+#include "sysemu/block-backend.h"
+#include "sysemu/block-ram-registrar.h"
+#include "qapi/error.h"
+
+static void ram_block_added(RAMBlockNotifier *n, void *host, size_t size,
+ size_t max_size)
+{
+ BlockRAMRegistrar *r = container_of(n, BlockRAMRegistrar, notifier);
+ Error *err = NULL;
+
+ if (!blk_register_buf(r->blk, host, max_size, &err)) {
+ error_report_err(err);
+ ram_block_notifier_remove(&r->notifier);
+ r->ok = false;
+ }
+}
+
+static void ram_block_removed(RAMBlockNotifier *n, void *host, size_t size,
+ size_t max_size)
+{
+ BlockRAMRegistrar *r = container_of(n, BlockRAMRegistrar, notifier);
+ blk_unregister_buf(r->blk, host, max_size);
+}
+
+void blk_ram_registrar_init(BlockRAMRegistrar *r, BlockBackend *blk)
+{
+ r->blk = blk;
+ r->notifier = (RAMBlockNotifier){
+ .ram_block_added = ram_block_added,
+ .ram_block_removed = ram_block_removed,
+
+ /*
+ * .ram_block_resized() is not necessary because we use the max_size
+ * value that does not change across resize.
+ */
+ };
+ r->ok = true;
+
+ ram_block_notifier_add(&r->notifier);
+}
+
+void blk_ram_registrar_destroy(BlockRAMRegistrar *r)
+{
+ if (r->ok) {
+ ram_block_notifier_remove(&r->notifier);
+ }
+}
diff --git a/block/meson.build b/block/meson.build
index 500878f082..b7c68b83a3 100644
--- a/block/meson.build
+++ b/block/meson.build
@@ -46,6 +46,7 @@ block_ss.add(files(
), zstd, zlib, gnutls)
softmmu_ss.add(when: 'CONFIG_TCG', if_true: files('blkreplay.c'))
+softmmu_ss.add(files('block-ram-registrar.c'))
if get_option('qcow1').allowed()
block_ss.add(files('qcow.c'))
--
2.37.2
^ permalink raw reply related [flat|nested] 23+ messages in thread
* [RFC v4 08/11] exec/cpu-common: add qemu_ram_get_fd()
2022-08-22 22:23 [RFC v4 00/11] blkio: add libblkio BlockDriver Stefan Hajnoczi
` (6 preceding siblings ...)
2022-08-22 22:23 ` [RFC v4 07/11] block: add BlockRAMRegistrar Stefan Hajnoczi
@ 2022-08-22 22:23 ` Stefan Hajnoczi
2022-08-22 22:24 ` [RFC v4 09/11] stubs: add qemu_ram_block_from_host() and qemu_ram_get_fd() Stefan Hajnoczi
` (3 subsequent siblings)
11 siblings, 0 replies; 23+ messages in thread
From: Stefan Hajnoczi @ 2022-08-22 22:23 UTC (permalink / raw)
To: qemu-devel
Cc: Paolo Bonzini, Denis V. Lunev, Peter Xu, Yanan Wang,
Marcel Apfelbaum, Richard W.M. Jones, qemu-block, John Snow,
integration, Vladimir Sementsov-Ogievskiy,
Vladimir Sementsov-Ogievskiy, David Hildenbrand, Laurent Vivier,
Markus Armbruster, Raphael Norwitz, Richard Henderson, Fam Zheng,
sgarzare, Alberto Faria, Kevin Wolf, Stefan Hajnoczi,
Wen Congyang, Eric Blake, Hanna Reitz,
Philippe Mathieu-Daudé,
Eduardo Habkost, Michael S. Tsirkin, Thomas Huth, Jeff Cody,
Xie Changlong
Add a function to get the file descriptor for a RAMBlock. Device
emulation code typically uses the MemoryRegion APIs but vhost-style code
may use RAMBlock directly for sharing guest memory with another process.
This new API will be used by the libblkio block driver so it can share
guest memory via .bdrv_register_buf().
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
include/exec/cpu-common.h | 1 +
softmmu/physmem.c | 5 +++++
2 files changed, 6 insertions(+)
diff --git a/include/exec/cpu-common.h b/include/exec/cpu-common.h
index 2281be4e10..ccef44b3d3 100644
--- a/include/exec/cpu-common.h
+++ b/include/exec/cpu-common.h
@@ -90,6 +90,7 @@ void qemu_ram_set_uf_zeroable(RAMBlock *rb);
bool qemu_ram_is_migratable(RAMBlock *rb);
void qemu_ram_set_migratable(RAMBlock *rb);
void qemu_ram_unset_migratable(RAMBlock *rb);
+int qemu_ram_get_fd(RAMBlock *rb);
size_t qemu_ram_pagesize(RAMBlock *block);
size_t qemu_ram_pagesize_largest(void);
diff --git a/softmmu/physmem.c b/softmmu/physmem.c
index dc3c3e5f2e..f2bdad2583 100644
--- a/softmmu/physmem.c
+++ b/softmmu/physmem.c
@@ -1765,6 +1765,11 @@ void qemu_ram_unset_migratable(RAMBlock *rb)
rb->flags &= ~RAM_MIGRATABLE;
}
+int qemu_ram_get_fd(RAMBlock *rb)
+{
+ return rb->fd;
+}
+
/* Called with iothread lock held. */
void qemu_ram_set_idstr(RAMBlock *new_block, const char *name, DeviceState *dev)
{
--
2.37.2
^ permalink raw reply related [flat|nested] 23+ messages in thread
* [RFC v4 09/11] stubs: add qemu_ram_block_from_host() and qemu_ram_get_fd()
2022-08-22 22:23 [RFC v4 00/11] blkio: add libblkio BlockDriver Stefan Hajnoczi
` (7 preceding siblings ...)
2022-08-22 22:23 ` [RFC v4 08/11] exec/cpu-common: add qemu_ram_get_fd() Stefan Hajnoczi
@ 2022-08-22 22:24 ` Stefan Hajnoczi
2022-08-22 22:24 ` [RFC v4 10/11] blkio: implement BDRV_REQ_REGISTERED_BUF optimization Stefan Hajnoczi
` (2 subsequent siblings)
11 siblings, 0 replies; 23+ messages in thread
From: Stefan Hajnoczi @ 2022-08-22 22:24 UTC (permalink / raw)
To: qemu-devel
Cc: Paolo Bonzini, Denis V. Lunev, Peter Xu, Yanan Wang,
Marcel Apfelbaum, Richard W.M. Jones, qemu-block, John Snow,
integration, Vladimir Sementsov-Ogievskiy,
Vladimir Sementsov-Ogievskiy, David Hildenbrand, Laurent Vivier,
Markus Armbruster, Raphael Norwitz, Richard Henderson, Fam Zheng,
sgarzare, Alberto Faria, Kevin Wolf, Stefan Hajnoczi,
Wen Congyang, Eric Blake, Hanna Reitz,
Philippe Mathieu-Daudé,
Eduardo Habkost, Michael S. Tsirkin, Thomas Huth, Jeff Cody,
Xie Changlong
The blkio block driver will need to look up the file descriptor for a
given pointer. This is possible in softmmu builds where the RAMBlock API
is available for querying guest RAM.
Add stubs so tools like qemu-img that link the block layer still build
successfully. In this case there is no guest RAM but that is fine.
Bounce buffers and their file descriptors will be allocated with
libblkio's blkio_alloc_mem_region() so we won't rely on QEMU's
qemu_ram_get_fd() in that case.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
stubs/physmem.c | 13 +++++++++++++
stubs/meson.build | 1 +
2 files changed, 14 insertions(+)
create mode 100644 stubs/physmem.c
diff --git a/stubs/physmem.c b/stubs/physmem.c
new file mode 100644
index 0000000000..1fc5f2df29
--- /dev/null
+++ b/stubs/physmem.c
@@ -0,0 +1,13 @@
+#include "qemu/osdep.h"
+#include "exec/cpu-common.h"
+
+RAMBlock *qemu_ram_block_from_host(void *ptr, bool round_offset,
+ ram_addr_t *offset)
+{
+ return NULL;
+}
+
+int qemu_ram_get_fd(RAMBlock *rb)
+{
+ return -1;
+}
diff --git a/stubs/meson.build b/stubs/meson.build
index d8f3fd5c44..4314161f5f 100644
--- a/stubs/meson.build
+++ b/stubs/meson.build
@@ -29,6 +29,7 @@ stub_ss.add(files('migr-blocker.c'))
stub_ss.add(files('module-opts.c'))
stub_ss.add(files('monitor.c'))
stub_ss.add(files('monitor-core.c'))
+stub_ss.add(files('physmem.c'))
stub_ss.add(files('qemu-timer-notify-cb.c'))
stub_ss.add(files('qmp_memory_device.c'))
stub_ss.add(files('qmp-command-available.c'))
--
2.37.2
^ permalink raw reply related [flat|nested] 23+ messages in thread
* [RFC v4 10/11] blkio: implement BDRV_REQ_REGISTERED_BUF optimization
2022-08-22 22:23 [RFC v4 00/11] blkio: add libblkio BlockDriver Stefan Hajnoczi
` (8 preceding siblings ...)
2022-08-22 22:24 ` [RFC v4 09/11] stubs: add qemu_ram_block_from_host() and qemu_ram_get_fd() Stefan Hajnoczi
@ 2022-08-22 22:24 ` Stefan Hajnoczi
2022-08-22 22:24 ` [RFC v4 11/11] virtio-blk: use BDRV_REQ_REGISTERED_BUF optimization hint Stefan Hajnoczi
2022-08-23 17:31 ` [RFC v4 00/11] blkio: add libblkio BlockDriver Vladimir Sementsov-Ogievskiy
11 siblings, 0 replies; 23+ messages in thread
From: Stefan Hajnoczi @ 2022-08-22 22:24 UTC (permalink / raw)
To: qemu-devel
Cc: Paolo Bonzini, Denis V. Lunev, Peter Xu, Yanan Wang,
Marcel Apfelbaum, Richard W.M. Jones, qemu-block, John Snow,
integration, Vladimir Sementsov-Ogievskiy,
Vladimir Sementsov-Ogievskiy, David Hildenbrand, Laurent Vivier,
Markus Armbruster, Raphael Norwitz, Richard Henderson, Fam Zheng,
sgarzare, Alberto Faria, Kevin Wolf, Stefan Hajnoczi,
Wen Congyang, Eric Blake, Hanna Reitz,
Philippe Mathieu-Daudé,
Eduardo Habkost, Michael S. Tsirkin, Thomas Huth, Jeff Cody,
Xie Changlong
Avoid bounce buffers when QEMUIOVector elements are within previously
registered bdrv_register_buf() buffers.
The idea is that emulated storage controllers will register guest RAM
using bdrv_register_buf() and set the BDRV_REQ_REGISTERED_BUF on I/O
requests. Therefore no blkio_map_mem_region() calls are necessary in the
performance-critical I/O code path.
This optimization doesn't apply if the I/O buffer is internally
allocated by QEMU (e.g. qcow2 metadata). There we still take the slow
path because BDRV_REQ_REGISTERED_BUF is not set.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
block/blkio.c | 142 ++++++++++++++++++++++++++++++++++++++++++++++++--
1 file changed, 139 insertions(+), 3 deletions(-)
diff --git a/block/blkio.c b/block/blkio.c
index cdcba1b63e..976d37705c 100644
--- a/block/blkio.c
+++ b/block/blkio.c
@@ -11,7 +11,10 @@
#include "qemu/osdep.h"
#include <blkio.h>
#include "block/block_int.h"
+#include "exec/memory.h"
+#include "exec/cpu-common.h" /* for qemu_ram_get_fd() */
#include "qapi/error.h"
+#include "qemu/error-report.h"
#include "qapi/qmp/qdict.h"
#include "qemu/module.h"
@@ -46,6 +49,9 @@ typedef struct {
/* Can we skip adding/deleting blkio_mem_regions? */
bool needs_mem_regions;
+
+ /* Are file descriptors necessary for blkio_mem_regions? */
+ bool needs_mem_region_fd;
} BDRVBlkioState;
static void blkio_aiocb_complete(BlkioAIOCB *acb, int ret)
@@ -226,6 +232,8 @@ static BlockAIOCB *blkio_aio_preadv(BlockDriverState *bs, int64_t offset,
BlockCompletionFunc *cb, void *opaque)
{
BDRVBlkioState *s = bs->opaque;
+ bool needs_mem_regions =
+ s->needs_mem_regions && !(flags & BDRV_REQ_REGISTERED_BUF);
struct iovec *iov = qiov->iov;
int iovcnt = qiov->niov;
BlkioAIOCB *acb;
@@ -234,7 +242,7 @@ static BlockAIOCB *blkio_aio_preadv(BlockDriverState *bs, int64_t offset,
acb = blkio_aiocb_get(bs, cb, opaque);
- if (s->needs_mem_regions) {
+ if (needs_mem_regions) {
if (blkio_aiocb_init_mem_region_locked(acb, bytes) < 0) {
qemu_aio_unref(&acb->common);
return NULL;
@@ -258,6 +266,8 @@ static BlockAIOCB *blkio_aio_pwritev(BlockDriverState *bs, int64_t offset,
{
uint32_t blkio_flags = (flags & BDRV_REQ_FUA) ? BLKIO_REQ_FUA : 0;
BDRVBlkioState *s = bs->opaque;
+ bool needs_mem_regions =
+ s->needs_mem_regions && !(flags & BDRV_REQ_REGISTERED_BUF);
struct iovec *iov = qiov->iov;
int iovcnt = qiov->niov;
BlkioAIOCB *acb;
@@ -266,7 +276,7 @@ static BlockAIOCB *blkio_aio_pwritev(BlockDriverState *bs, int64_t offset,
acb = blkio_aiocb_get(bs, cb, opaque);
- if (s->needs_mem_regions) {
+ if (needs_mem_regions) {
if (blkio_aiocb_init_mem_region_locked(acb, bytes) < 0) {
qemu_aio_unref(&acb->common);
return NULL;
@@ -352,6 +362,117 @@ static void blkio_io_unplug(BlockDriverState *bs)
}
}
+typedef enum {
+ BMRR_OK,
+ BMRR_SKIP,
+ BMRR_FAIL,
+} BlkioMemRegionResult;
+
+/*
+ * Produce a struct blkio_mem_region for a given address and size.
+ *
+ * This function produces identical results when called multiple times with the
+ * same arguments. This property is necessary because blkio_unmap_mem_region()
+ * must receive the same struct blkio_mem_region field values that were passed
+ * to blkio_map_mem_region().
+ */
+static BlkioMemRegionResult
+blkio_mem_region_from_host(BlockDriverState *bs,
+ void *host, size_t size,
+ struct blkio_mem_region *region,
+ Error **errp)
+{
+ BDRVBlkioState *s = bs->opaque;
+ int fd = -1;
+ ram_addr_t fd_offset = 0;
+
+ if (((uintptr_t)host | size) % s->mem_region_alignment) {
+ error_setg(errp, "unaligned buf %p with size %zu", host, size);
+ return BMRR_FAIL;
+ }
+
+ /* Attempt to find the fd for the underlying memory */
+ if (s->needs_mem_region_fd) {
+ RAMBlock *ram_block;
+ RAMBlock *end_block;
+ ram_addr_t offset;
+
+ /*
+ * bdrv_register_buf() is called with the BQL held so mr lives at least
+ * until this function returns.
+ */
+ ram_block = qemu_ram_block_from_host(host, false, &fd_offset);
+ if (ram_block) {
+ fd = qemu_ram_get_fd(ram_block);
+ }
+ if (fd == -1) {
+ /*
+ * Ideally every RAMBlock would have an fd. pc-bios and other
+ * things don't. Luckily they are usually not I/O buffers and we
+ * can just ignore them.
+ */
+ return BMRR_SKIP;
+ }
+
+ /* Make sure the fd covers the entire range */
+ end_block = qemu_ram_block_from_host(host + size - 1, false, &offset);
+ if (ram_block != end_block) {
+ error_setg(errp, "registered buffer at %p with size %zu extends "
+ "beyond RAMBlock", host, size);
+ return BMRR_FAIL;
+ }
+ }
+
+ *region = (struct blkio_mem_region){
+ .addr = host,
+ .len = size,
+ .fd = fd,
+ .fd_offset = fd_offset,
+ };
+ return BMRR_OK;
+}
+
+static bool blkio_register_buf(BlockDriverState *bs, void *host, size_t size,
+ Error **errp)
+{
+ BDRVBlkioState *s = bs->opaque;
+ struct blkio_mem_region region;
+ BlkioMemRegionResult region_result;
+ int ret;
+
+ region_result = blkio_mem_region_from_host(bs, host, size, ®ion, errp);
+ if (region_result == BMRR_SKIP) {
+ return true;
+ } else if (region_result != BMRR_OK) {
+ return false;
+ }
+
+ WITH_QEMU_LOCK_GUARD(&s->lock) {
+ ret = blkio_map_mem_region(s->blkio, ®ion);
+ }
+
+ if (ret < 0) {
+ error_setg(errp, "Failed to add blkio mem region %p with size %zu: %s",
+ host, size, blkio_get_error_msg());
+ return false;
+ }
+ return true;
+}
+
+static void blkio_unregister_buf(BlockDriverState *bs, void *host, size_t size)
+{
+ BDRVBlkioState *s = bs->opaque;
+ struct blkio_mem_region region;
+
+ if (blkio_mem_region_from_host(bs, host, size, ®ion, NULL) != BMRR_OK) {
+ return;
+ }
+
+ WITH_QEMU_LOCK_GUARD(&s->lock) {
+ blkio_unmap_mem_region(s->blkio, ®ion);
+ }
+}
+
static int blkio_io_uring_open(BlockDriverState *bs, QDict *options, int flags,
Error **errp)
{
@@ -490,6 +611,17 @@ static int blkio_file_open(BlockDriverState *bs, QDict *options, int flags,
return ret;
}
+ ret = blkio_get_bool(s->blkio,
+ "needs-mem-region-fd",
+ &s->needs_mem_region_fd);
+ if (ret < 0) {
+ error_setg_errno(errp, -ret,
+ "failed to get needs-mem-region-fd: %s",
+ blkio_get_error_msg());
+ blkio_destroy(&s->blkio);
+ return ret;
+ }
+
ret = blkio_get_uint64(s->blkio,
"mem-region-alignment",
&s->mem_region_alignment);
@@ -509,7 +641,7 @@ static int blkio_file_open(BlockDriverState *bs, QDict *options, int flags,
return ret;
}
- bs->supported_write_flags = BDRV_REQ_FUA;
+ bs->supported_write_flags = BDRV_REQ_FUA | BDRV_REQ_REGISTERED_BUF;
bs->supported_zero_flags = BDRV_REQ_FUA | BDRV_REQ_MAY_UNMAP |
BDRV_REQ_NO_FALLBACK;
@@ -673,6 +805,8 @@ static BlockDriver bdrv_io_uring = {
.bdrv_co_pwrite_zeroes = blkio_co_pwrite_zeroes,
.bdrv_io_unplug = blkio_io_unplug,
.bdrv_refresh_limits = blkio_refresh_limits,
+ .bdrv_register_buf = blkio_register_buf,
+ .bdrv_unregister_buf = blkio_unregister_buf,
};
static BlockDriver bdrv_virtio_blk_vhost_user = {
@@ -713,6 +847,8 @@ static BlockDriver bdrv_virtio_blk_vhost_vdpa = {
.bdrv_co_pwrite_zeroes = blkio_co_pwrite_zeroes,
.bdrv_io_unplug = blkio_io_unplug,
.bdrv_refresh_limits = blkio_refresh_limits,
+ .bdrv_register_buf = blkio_register_buf,
+ .bdrv_unregister_buf = blkio_unregister_buf,
};
static void bdrv_blkio_init(void)
--
2.37.2
^ permalink raw reply related [flat|nested] 23+ messages in thread
* [RFC v4 11/11] virtio-blk: use BDRV_REQ_REGISTERED_BUF optimization hint
2022-08-22 22:23 [RFC v4 00/11] blkio: add libblkio BlockDriver Stefan Hajnoczi
` (9 preceding siblings ...)
2022-08-22 22:24 ` [RFC v4 10/11] blkio: implement BDRV_REQ_REGISTERED_BUF optimization Stefan Hajnoczi
@ 2022-08-22 22:24 ` Stefan Hajnoczi
2022-08-23 8:01 ` David Hildenbrand
2022-08-23 17:31 ` [RFC v4 00/11] blkio: add libblkio BlockDriver Vladimir Sementsov-Ogievskiy
11 siblings, 1 reply; 23+ messages in thread
From: Stefan Hajnoczi @ 2022-08-22 22:24 UTC (permalink / raw)
To: qemu-devel
Cc: Paolo Bonzini, Denis V. Lunev, Peter Xu, Yanan Wang,
Marcel Apfelbaum, Richard W.M. Jones, qemu-block, John Snow,
integration, Vladimir Sementsov-Ogievskiy,
Vladimir Sementsov-Ogievskiy, David Hildenbrand, Laurent Vivier,
Markus Armbruster, Raphael Norwitz, Richard Henderson, Fam Zheng,
sgarzare, Alberto Faria, Kevin Wolf, Stefan Hajnoczi,
Wen Congyang, Eric Blake, Hanna Reitz,
Philippe Mathieu-Daudé,
Eduardo Habkost, Michael S. Tsirkin, Thomas Huth, Jeff Cody,
Xie Changlong
Register guest RAM using BlockRAMRegistrar and set the
BDRV_REQ_REGISTERED_BUF flag so block drivers can optimize memory
accesses in I/O requests.
This is for vdpa-blk, vhost-user-blk, and other I/O interfaces that rely
on DMA mapping/unmapping.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
include/hw/virtio/virtio-blk.h | 2 ++
hw/block/virtio-blk.c | 39 ++++++++++++++++++++++------------
2 files changed, 27 insertions(+), 14 deletions(-)
diff --git a/include/hw/virtio/virtio-blk.h b/include/hw/virtio/virtio-blk.h
index d311c57cca..7f589b4146 100644
--- a/include/hw/virtio/virtio-blk.h
+++ b/include/hw/virtio/virtio-blk.h
@@ -19,6 +19,7 @@
#include "hw/block/block.h"
#include "sysemu/iothread.h"
#include "sysemu/block-backend.h"
+#include "sysemu/block-ram-registrar.h"
#include "qom/object.h"
#define TYPE_VIRTIO_BLK "virtio-blk-device"
@@ -64,6 +65,7 @@ struct VirtIOBlock {
struct VirtIOBlockDataPlane *dataplane;
uint64_t host_features;
size_t config_size;
+ BlockRAMRegistrar blk_ram_registrar;
};
typedef struct VirtIOBlockReq {
diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c
index e9ba752f6b..907f012c45 100644
--- a/hw/block/virtio-blk.c
+++ b/hw/block/virtio-blk.c
@@ -21,6 +21,7 @@
#include "hw/block/block.h"
#include "hw/qdev-properties.h"
#include "sysemu/blockdev.h"
+#include "sysemu/block-ram-registrar.h"
#include "sysemu/sysemu.h"
#include "sysemu/runstate.h"
#include "hw/virtio/virtio-blk.h"
@@ -384,12 +385,14 @@ static void virtio_blk_handle_scsi(VirtIOBlockReq *req)
}
}
-static inline void submit_requests(BlockBackend *blk, MultiReqBuffer *mrb,
+static inline void submit_requests(VirtIOBlock *s, MultiReqBuffer *mrb,
int start, int num_reqs, int niov)
{
+ BlockBackend *blk = s->blk;
QEMUIOVector *qiov = &mrb->reqs[start]->qiov;
int64_t sector_num = mrb->reqs[start]->sector_num;
bool is_write = mrb->is_write;
+ BdrvRequestFlags flags = 0;
if (num_reqs > 1) {
int i;
@@ -420,12 +423,18 @@ static inline void submit_requests(BlockBackend *blk, MultiReqBuffer *mrb,
num_reqs - 1);
}
+ if (blk_ram_registrar_ok(&s->blk_ram_registrar)) {
+ flags |= BDRV_REQ_REGISTERED_BUF;
+ }
+
if (is_write) {
- blk_aio_pwritev(blk, sector_num << BDRV_SECTOR_BITS, qiov, 0,
- virtio_blk_rw_complete, mrb->reqs[start]);
+ blk_aio_pwritev(blk, sector_num << BDRV_SECTOR_BITS, qiov,
+ flags, virtio_blk_rw_complete,
+ mrb->reqs[start]);
} else {
- blk_aio_preadv(blk, sector_num << BDRV_SECTOR_BITS, qiov, 0,
- virtio_blk_rw_complete, mrb->reqs[start]);
+ blk_aio_preadv(blk, sector_num << BDRV_SECTOR_BITS, qiov,
+ flags, virtio_blk_rw_complete,
+ mrb->reqs[start]);
}
}
@@ -447,14 +456,14 @@ static int multireq_compare(const void *a, const void *b)
}
}
-static void virtio_blk_submit_multireq(BlockBackend *blk, MultiReqBuffer *mrb)
+static void virtio_blk_submit_multireq(VirtIOBlock *s, MultiReqBuffer *mrb)
{
int i = 0, start = 0, num_reqs = 0, niov = 0, nb_sectors = 0;
uint32_t max_transfer;
int64_t sector_num = 0;
if (mrb->num_reqs == 1) {
- submit_requests(blk, mrb, 0, 1, -1);
+ submit_requests(s, mrb, 0, 1, -1);
mrb->num_reqs = 0;
return;
}
@@ -474,11 +483,11 @@ static void virtio_blk_submit_multireq(BlockBackend *blk, MultiReqBuffer *mrb)
* 3. merge would exceed maximum transfer length of backend device
*/
if (sector_num + nb_sectors != req->sector_num ||
- niov > blk_get_max_iov(blk) - req->qiov.niov ||
+ niov > blk_get_max_iov(s->blk) - req->qiov.niov ||
req->qiov.size > max_transfer ||
nb_sectors > (max_transfer -
req->qiov.size) / BDRV_SECTOR_SIZE) {
- submit_requests(blk, mrb, start, num_reqs, niov);
+ submit_requests(s, mrb, start, num_reqs, niov);
num_reqs = 0;
}
}
@@ -494,7 +503,7 @@ static void virtio_blk_submit_multireq(BlockBackend *blk, MultiReqBuffer *mrb)
num_reqs++;
}
- submit_requests(blk, mrb, start, num_reqs, niov);
+ submit_requests(s, mrb, start, num_reqs, niov);
mrb->num_reqs = 0;
}
@@ -509,7 +518,7 @@ static void virtio_blk_handle_flush(VirtIOBlockReq *req, MultiReqBuffer *mrb)
* Make sure all outstanding writes are posted to the backing device.
*/
if (mrb->is_write && mrb->num_reqs > 0) {
- virtio_blk_submit_multireq(s->blk, mrb);
+ virtio_blk_submit_multireq(s, mrb);
}
blk_aio_flush(s->blk, virtio_blk_flush_complete, req);
}
@@ -689,7 +698,7 @@ static int virtio_blk_handle_request(VirtIOBlockReq *req, MultiReqBuffer *mrb)
if (mrb->num_reqs > 0 && (mrb->num_reqs == VIRTIO_BLK_MAX_MERGE_REQS ||
is_write != mrb->is_write ||
!s->conf.request_merging)) {
- virtio_blk_submit_multireq(s->blk, mrb);
+ virtio_blk_submit_multireq(s, mrb);
}
assert(mrb->num_reqs < VIRTIO_BLK_MAX_MERGE_REQS);
@@ -796,7 +805,7 @@ void virtio_blk_handle_vq(VirtIOBlock *s, VirtQueue *vq)
} while (!virtio_queue_empty(vq));
if (mrb.num_reqs) {
- virtio_blk_submit_multireq(s->blk, &mrb);
+ virtio_blk_submit_multireq(s, &mrb);
}
blk_io_unplug(s->blk);
@@ -845,7 +854,7 @@ void virtio_blk_process_queued_requests(VirtIOBlock *s, bool is_bh)
}
if (mrb.num_reqs) {
- virtio_blk_submit_multireq(s->blk, &mrb);
+ virtio_blk_submit_multireq(s, &mrb);
}
if (is_bh) {
blk_dec_in_flight(s->conf.conf.blk);
@@ -1227,6 +1236,7 @@ static void virtio_blk_device_realize(DeviceState *dev, Error **errp)
}
s->change = qemu_add_vm_change_state_handler(virtio_blk_dma_restart_cb, s);
+ blk_ram_registrar_init(&s->blk_ram_registrar, s->blk);
blk_set_dev_ops(s->blk, &virtio_block_ops, s);
blk_iostatus_enable(s->blk);
@@ -1252,6 +1262,7 @@ static void virtio_blk_device_unrealize(DeviceState *dev)
virtio_del_queue(vdev, i);
}
qemu_coroutine_dec_pool_size(conf->num_queues * conf->queue_size / 2);
+ blk_ram_registrar_destroy(&s->blk_ram_registrar);
qemu_del_vm_change_state_handler(s->change);
blockdev_mark_auto_del(s->blk);
virtio_cleanup(vdev);
--
2.37.2
^ permalink raw reply related [flat|nested] 23+ messages in thread
* Re: [RFC v4 11/11] virtio-blk: use BDRV_REQ_REGISTERED_BUF optimization hint
2022-08-22 22:24 ` [RFC v4 11/11] virtio-blk: use BDRV_REQ_REGISTERED_BUF optimization hint Stefan Hajnoczi
@ 2022-08-23 8:01 ` David Hildenbrand
2022-08-23 19:22 ` Stefan Hajnoczi
0 siblings, 1 reply; 23+ messages in thread
From: David Hildenbrand @ 2022-08-23 8:01 UTC (permalink / raw)
To: Stefan Hajnoczi, qemu-devel
Cc: Paolo Bonzini, Denis V. Lunev, Peter Xu, Yanan Wang,
Marcel Apfelbaum, Richard W.M. Jones, qemu-block, John Snow,
integration, Vladimir Sementsov-Ogievskiy,
Vladimir Sementsov-Ogievskiy, Laurent Vivier, Markus Armbruster,
Raphael Norwitz, Richard Henderson, Fam Zheng, sgarzare,
Alberto Faria, Kevin Wolf, Wen Congyang, Eric Blake, Hanna Reitz,
Philippe Mathieu-Daudé,
Eduardo Habkost, Michael S. Tsirkin, Thomas Huth, Jeff Cody,
Xie Changlong
On 23.08.22 00:24, Stefan Hajnoczi wrote:
> Register guest RAM using BlockRAMRegistrar and set the
> BDRV_REQ_REGISTERED_BUF flag so block drivers can optimize memory
> accesses in I/O requests.
>
> This is for vdpa-blk, vhost-user-blk, and other I/O interfaces that rely
> on DMA mapping/unmapping.
Can you explain why we're monitoring RAMRegistrar to hook into "guest
RAM" and not go the usual path of the MemoryListener?
What will BDRV_REQ_REGISTERED_BUF actually do? Pin all guest memory in
the worst case such as io_uring fixed buffers would do ( I hope not ).
--
Thanks,
David / dhildenb
^ permalink raw reply [flat|nested] 23+ messages in thread
* Re: [RFC v4 00/11] blkio: add libblkio BlockDriver
2022-08-22 22:23 [RFC v4 00/11] blkio: add libblkio BlockDriver Stefan Hajnoczi
` (10 preceding siblings ...)
2022-08-22 22:24 ` [RFC v4 11/11] virtio-blk: use BDRV_REQ_REGISTERED_BUF optimization hint Stefan Hajnoczi
@ 2022-08-23 17:31 ` Vladimir Sementsov-Ogievskiy
2022-08-23 20:35 ` Stefan Hajnoczi
2022-08-31 19:44 ` Stefan Hajnoczi
11 siblings, 2 replies; 23+ messages in thread
From: Vladimir Sementsov-Ogievskiy @ 2022-08-23 17:31 UTC (permalink / raw)
To: Stefan Hajnoczi, qemu-devel
Cc: Paolo Bonzini, Denis V. Lunev, Peter Xu, Yanan Wang,
Marcel Apfelbaum, Richard W.M. Jones, qemu-block, John Snow,
integration, Vladimir Sementsov-Ogievskiy, David Hildenbrand,
Laurent Vivier, Markus Armbruster, Raphael Norwitz,
Richard Henderson, Fam Zheng, sgarzare, Alberto Faria,
Kevin Wolf, Wen Congyang, Eric Blake, Hanna Reitz,
Philippe Mathieu-Daudé,
Eduardo Habkost, Michael S. Tsirkin, Thomas Huth, Jeff Cody,
Xie Changlong
On 8/23/22 01:23, Stefan Hajnoczi wrote:
> The remainder of the patch series reworks the existing QEMU bdrv_register_buf()
> API so virtio-blk emulation efficiently map guest RAM for libblkio - some
> libblkio drivers require that I/O buffer memory is pre-registered (think VFIO,
> vhost, etc).
Hi!
So patches 01-11 are for performance optimization? Don't you have some performance measurements for it?
--
Best regards,
Vladimir
^ permalink raw reply [flat|nested] 23+ messages in thread
* Re: [RFC v4 11/11] virtio-blk: use BDRV_REQ_REGISTERED_BUF optimization hint
2022-08-23 8:01 ` David Hildenbrand
@ 2022-08-23 19:22 ` Stefan Hajnoczi
2022-08-25 7:43 ` David Hildenbrand
0 siblings, 1 reply; 23+ messages in thread
From: Stefan Hajnoczi @ 2022-08-23 19:22 UTC (permalink / raw)
To: David Hildenbrand
Cc: qemu-devel, Paolo Bonzini, Denis V. Lunev, Peter Xu, Yanan Wang,
Marcel Apfelbaum, Richard W.M. Jones, qemu-block, John Snow,
integration, Vladimir Sementsov-Ogievskiy,
Vladimir Sementsov-Ogievskiy, Laurent Vivier, Markus Armbruster,
Raphael Norwitz, Richard Henderson, Fam Zheng, sgarzare,
Alberto Faria, Kevin Wolf, Wen Congyang, Eric Blake, Hanna Reitz,
Philippe Mathieu-Daudé,
Eduardo Habkost, Michael S. Tsirkin, Thomas Huth, Jeff Cody,
Xie Changlong
[-- Attachment #1: Type: text/plain, Size: 1479 bytes --]
On Tue, Aug 23, 2022 at 10:01:59AM +0200, David Hildenbrand wrote:
> On 23.08.22 00:24, Stefan Hajnoczi wrote:
> > Register guest RAM using BlockRAMRegistrar and set the
> > BDRV_REQ_REGISTERED_BUF flag so block drivers can optimize memory
> > accesses in I/O requests.
> >
> > This is for vdpa-blk, vhost-user-blk, and other I/O interfaces that rely
> > on DMA mapping/unmapping.
>
> Can you explain why we're monitoring RAMRegistrar to hook into "guest
> RAM" and not go the usual path of the MemoryListener?
The requirements are similar to VFIO, which uses RAMBlockNotifier. We
need to learn about all guest RAM because that's where I/O buffers are
located.
Do you think RAMBlockNotifier should be avoided?
> What will BDRV_REQ_REGISTERED_BUF actually do? Pin all guest memory in
> the worst case such as io_uring fixed buffers would do ( I hope not ).
BLK_REQ_REGISTERED_BUF is a hint that no bounce buffer is necessary
because the I/O buffer is located in memory that was previously
registered with bdrv_registered_buf().
The RAMBlockNotifier calls bdrv_register_buf() to let the libblkio
driver know about RAM. Some libblkio drivers ignore this hint, io_uring
may use the fixed buffers feature, vhost-user sends the shared memory
file descriptors to the vhost device server, and VFIO/vhost may pin
pages.
So the blkio block driver doesn't add anything new, it's the union of
VFIO/vhost/vhost-user/etc memory requirements.
Stefan
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^ permalink raw reply [flat|nested] 23+ messages in thread
* Re: [RFC v4 00/11] blkio: add libblkio BlockDriver
2022-08-23 17:31 ` [RFC v4 00/11] blkio: add libblkio BlockDriver Vladimir Sementsov-Ogievskiy
@ 2022-08-23 20:35 ` Stefan Hajnoczi
2022-08-31 19:44 ` Stefan Hajnoczi
1 sibling, 0 replies; 23+ messages in thread
From: Stefan Hajnoczi @ 2022-08-23 20:35 UTC (permalink / raw)
To: Vladimir Sementsov-Ogievskiy
Cc: qemu-devel, Paolo Bonzini, Denis V. Lunev, Peter Xu, Yanan Wang,
Marcel Apfelbaum, Richard W.M. Jones, qemu-block, John Snow,
integration, Vladimir Sementsov-Ogievskiy, David Hildenbrand,
Laurent Vivier, Markus Armbruster, Raphael Norwitz,
Richard Henderson, Fam Zheng, sgarzare, Alberto Faria,
Kevin Wolf, Wen Congyang, Eric Blake, Hanna Reitz,
Philippe Mathieu-Daudé,
Eduardo Habkost, Michael S. Tsirkin, Thomas Huth, Jeff Cody,
Xie Changlong
[-- Attachment #1: Type: text/plain, Size: 572 bytes --]
On Tue, Aug 23, 2022 at 08:31:03PM +0300, Vladimir Sementsov-Ogievskiy wrote:
> On 8/23/22 01:23, Stefan Hajnoczi wrote:
> > The remainder of the patch series reworks the existing QEMU bdrv_register_buf()
> > API so virtio-blk emulation efficiently map guest RAM for libblkio - some
> > libblkio drivers require that I/O buffer memory is pre-registered (think VFIO,
> > vhost, etc).
>
> Hi!
>
> So patches 01-11 are for performance optimization? Don't you have some performance measurements for it?
Good point, I'll gather some data and share it.
Stefan
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^ permalink raw reply [flat|nested] 23+ messages in thread
* Re: [RFC v4 11/11] virtio-blk: use BDRV_REQ_REGISTERED_BUF optimization hint
2022-08-23 19:22 ` Stefan Hajnoczi
@ 2022-08-25 7:43 ` David Hildenbrand
2022-08-30 20:16 ` Stefan Hajnoczi
0 siblings, 1 reply; 23+ messages in thread
From: David Hildenbrand @ 2022-08-25 7:43 UTC (permalink / raw)
To: Stefan Hajnoczi
Cc: qemu-devel, Paolo Bonzini, Denis V. Lunev, Peter Xu, Yanan Wang,
Marcel Apfelbaum, Richard W.M. Jones, qemu-block, John Snow,
integration, Vladimir Sementsov-Ogievskiy,
Vladimir Sementsov-Ogievskiy, Laurent Vivier, Markus Armbruster,
Raphael Norwitz, Richard Henderson, Fam Zheng, sgarzare,
Alberto Faria, Kevin Wolf, Wen Congyang, Eric Blake, Hanna Reitz,
Philippe Mathieu-Daudé,
Eduardo Habkost, Michael S. Tsirkin, Thomas Huth, Jeff Cody,
Xie Changlong
On 23.08.22 21:22, Stefan Hajnoczi wrote:
> On Tue, Aug 23, 2022 at 10:01:59AM +0200, David Hildenbrand wrote:
>> On 23.08.22 00:24, Stefan Hajnoczi wrote:
>>> Register guest RAM using BlockRAMRegistrar and set the
>>> BDRV_REQ_REGISTERED_BUF flag so block drivers can optimize memory
>>> accesses in I/O requests.
>>>
>>> This is for vdpa-blk, vhost-user-blk, and other I/O interfaces that rely
>>> on DMA mapping/unmapping.
>>
>> Can you explain why we're monitoring RAMRegistrar to hook into "guest
>> RAM" and not go the usual path of the MemoryListener?
>
> The requirements are similar to VFIO, which uses RAMBlockNotifier. We
Only VFIO NVME uses RAMBlockNotifier. Ordinary VFIO uses the MemoryListener.
Maybe the difference is that ordinary VFIO has to replicate the actual
guest physical memory layout, and VFIO NVME is only interested in
possible guest RAM inside guest physical memory.
> need to learn about all guest RAM because that's where I/O buffers are
> located.
>
> Do you think RAMBlockNotifier should be avoided?
I assume it depends on the use case. For saying "this might be used for
I/O" it might be good enough I guess.
>
>> What will BDRV_REQ_REGISTERED_BUF actually do? Pin all guest memory in
>> the worst case such as io_uring fixed buffers would do ( I hope not ).
>
> BLK_REQ_REGISTERED_BUF is a hint that no bounce buffer is necessary
> because the I/O buffer is located in memory that was previously
> registered with bdrv_registered_buf().
>
> The RAMBlockNotifier calls bdrv_register_buf() to let the libblkio
> driver know about RAM. Some libblkio drivers ignore this hint, io_uring
> may use the fixed buffers feature, vhost-user sends the shared memory
> file descriptors to the vhost device server, and VFIO/vhost may pin
> pages.
>
> So the blkio block driver doesn't add anything new, it's the union of
> VFIO/vhost/vhost-user/etc memory requirements.
The issue is if that backend pins memory inside any of these regions.
Then, you're instantly incompatible to anything the relies on sparse
RAMBlocks, such as memory ballooning or virtio-mem, and have to properly
fence it.
In that case, you'd have to successfully trigger
ram_block_discard_disable(true) first, before pinning. Who would do that
now conditionally, just like e.g., VFIO does?
io_uring fixed buffers would be one such example that pins memory and is
problematic. vfio (unless on s390x) is another example, as you point out.
This has to be treated with care. Another thing to consider is that
different backends might only support a limited number of such regions.
I assume there is a way for QEMU to query this limit upfront? It might
be required for memory hot(un)plug to figure out how many memory slots
we actually have (for ordinary DIMMs, and if we ever want to make this
compatible to virtio-mem, it might be required as well when the backend
pins memory).
--
Thanks,
David / dhildenb
^ permalink raw reply [flat|nested] 23+ messages in thread
* Re: [RFC v4 01/11] blkio: add libblkio block driver
2022-08-22 22:23 ` [RFC v4 01/11] blkio: add libblkio block driver Stefan Hajnoczi
@ 2022-08-30 7:30 ` Markus Armbruster
2022-08-30 20:18 ` Stefan Hajnoczi
0 siblings, 1 reply; 23+ messages in thread
From: Markus Armbruster @ 2022-08-30 7:30 UTC (permalink / raw)
To: Stefan Hajnoczi
Cc: qemu-devel, Paolo Bonzini, Denis V. Lunev, Peter Xu, Yanan Wang,
Marcel Apfelbaum, Richard W.M. Jones, qemu-block, John Snow,
integration, Vladimir Sementsov-Ogievskiy,
Vladimir Sementsov-Ogievskiy, David Hildenbrand, Laurent Vivier,
Raphael Norwitz, Richard Henderson, Fam Zheng, sgarzare,
Alberto Faria, Kevin Wolf, Wen Congyang, Eric Blake, Hanna Reitz,
Philippe Mathieu-Daudé,
Eduardo Habkost, Michael S. Tsirkin, Thomas Huth, Jeff Cody,
Xie Changlong
Stefan Hajnoczi <stefanha@redhat.com> writes:
> libblkio (https://gitlab.com/libblkio/libblkio/) is a library for
> high-performance disk I/O. It currently supports io_uring,
> virtio-blk-vhost-user, and virtio-blk-vhost-vdpa with additional drivers
> under development.
>
> One of the reasons for developing libblkio is that other applications
> besides QEMU can use it. This will be particularly useful for
> virtio-blk-vhost-user which applications may wish to use for connecting
> to qemu-storage-daemon.
>
> libblkio also gives us an opportunity to develop in Rust behind a C API
> that is easy to consume from QEMU.
>
> This commit adds io_uring, virtio-blk-vhost-user, and
> virtio-blk-vhost-vdpa BlockDrivers to QEMU using libblkio. It will be
> easy to add other libblkio drivers since they will share the majority of
> code.
>
> For now I/O buffers are copied through bounce buffers if the libblkio
> driver requires it. Later commits add an optimization for
> pre-registering guest RAM to avoid bounce buffers.
>
> The syntax is:
>
> --blockdev io_uring,node-name=drive0,filename=test.img,readonly=on|off,cache.direct=on|off
>
> and:
>
> --blockdev virtio-blk-vhost-vdpa,node-name=drive0,path=/dev/vdpa...,readonly=on|off
>
> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> ---
> MAINTAINERS | 6 +
> meson_options.txt | 2 +
> qapi/block-core.json | 53 ++-
> meson.build | 9 +
> block/blkio.c | 725 ++++++++++++++++++++++++++++++++++
> tests/qtest/modules-test.c | 3 +
> block/meson.build | 1 +
> scripts/meson-buildoptions.sh | 3 +
> 8 files changed, 800 insertions(+), 2 deletions(-)
> create mode 100644 block/blkio.c
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 5ce4227ff6..f8ccd5954c 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -3397,6 +3397,12 @@ L: qemu-block@nongnu.org
> S: Maintained
> F: block/vdi.c
>
> +blkio
> +M: Stefan Hajnoczi <stefanha@redhat.com>
> +L: qemu-block@nongnu.org
> +S: Maintained
> +F: block/blkio.c
> +
> iSCSI
> M: Ronnie Sahlberg <ronniesahlberg@gmail.com>
> M: Paolo Bonzini <pbonzini@redhat.com>
> diff --git a/meson_options.txt b/meson_options.txt
> index e58e158396..67d841a8d2 100644
> --- a/meson_options.txt
> +++ b/meson_options.txt
> @@ -117,6 +117,8 @@ option('bzip2', type : 'feature', value : 'auto',
> description: 'bzip2 support for DMG images')
> option('cap_ng', type : 'feature', value : 'auto',
> description: 'cap_ng support')
> +option('blkio', type : 'feature', value : 'auto',
> + description: 'libblkio block device driver')
> option('bpf', type : 'feature', value : 'auto',
> description: 'eBPF support')
> option('cocoa', type : 'feature', value : 'auto',
> diff --git a/qapi/block-core.json b/qapi/block-core.json
> index 2173e7734a..c8d217b50c 100644
> --- a/qapi/block-core.json
> +++ b/qapi/block-core.json
> @@ -2951,11 +2951,16 @@
> 'file', 'snapshot-access', 'ftp', 'ftps', 'gluster',
> {'name': 'host_cdrom', 'if': 'HAVE_HOST_BLOCK_DEVICE' },
> {'name': 'host_device', 'if': 'HAVE_HOST_BLOCK_DEVICE' },
> - 'http', 'https', 'iscsi',
> + 'http', 'https',
> + { 'name': 'io_uring', 'if': 'CONFIG_BLKIO' },
> + 'iscsi',
> 'luks', 'nbd', 'nfs', 'null-aio', 'null-co', 'nvme', 'parallels',
> 'preallocate', 'qcow', 'qcow2', 'qed', 'quorum', 'raw', 'rbd',
> { 'name': 'replication', 'if': 'CONFIG_REPLICATION' },
> - 'ssh', 'throttle', 'vdi', 'vhdx', 'vmdk', 'vpc', 'vvfat' ] }
> + 'ssh', 'throttle', 'vdi', 'vhdx',
> + { 'name': 'virtio-blk-vhost-user', 'if': 'CONFIG_BLKIO' },
> + { 'name': 'virtio-blk-vhost-vdpa', 'if': 'CONFIG_BLKIO' },
> + 'vmdk', 'vpc', 'vvfat' ] }
>
> ##
> # @BlockdevOptionsFile:
> @@ -3678,6 +3683,42 @@
> '*debug': 'int',
> '*logfile': 'str' } }
>
> +##
> +# @BlockdevOptionsIoUring:
> +#
> +# Driver specific block device options for the io_uring backend.
> +#
> +# @filename: path to the image file
> +#
> +# Since: 7.2
> +##
> +{ 'struct': 'BlockdevOptionsIoUring',
> + 'data': { 'filename': 'str' } }
> +
> +##
> +# @BlockdevOptionsVirtioBlkVhostUser:
> +#
> +# Driver specific block device options for the virtio-blk-vhost-user backend.
> +#
> +# @path: path to the vhost-user UNIX domain socket.
> +#
> +# Since: 7.2
> +##
> +{ 'struct': 'BlockdevOptionsVirtioBlkVhostUser',
> + 'data': { 'path': 'str' } }
> +
> +##
> +# @BlockdevOptionsVirtioBlkVhostVdpa:
> +#
> +# Driver specific block device options for the virtio-blk-vhost-vdpa backend.
> +#
> +# @path: path to the vhost-vdpa character device.
> +#
> +# Since: 7.2
> +##
> +{ 'struct': 'BlockdevOptionsVirtioBlkVhostVdpa',
> + 'data': { 'path': 'str' } }
> +
We seem to be evenly split between 'filename' and 'path'. Before the
patch we have four uses of 'filename' in this schema file (ImageInfo,
ImageCheck, BlockDriverOptionsFile, BlockdevCreateOptionsFile), and
three of 'path' (BlockdevOptionsSsh, BlockdevOptionsGluster,
BlockdevOptionsNfs). There's also 'backing-file', 'data-file',
'backing-filename', 'file', and probably more (I stopped looking).
I dislike 'path'. For what it's worth, POSIX calls this "pathname", and
the components "filename". Everyday use hardly ever distinguishes
between the two. Plain "path", however, is commonly used for lists of
directories.
> ##
> # @IscsiTransport:
> #
> @@ -4305,6 +4346,8 @@
> 'if': 'HAVE_HOST_BLOCK_DEVICE' },
> 'http': 'BlockdevOptionsCurlHttp',
> 'https': 'BlockdevOptionsCurlHttps',
> + 'io_uring': { 'type': 'BlockdevOptionsIoUring',
> + 'if': 'CONFIG_BLKIO' },
> 'iscsi': 'BlockdevOptionsIscsi',
> 'luks': 'BlockdevOptionsLUKS',
> 'nbd': 'BlockdevOptionsNbd',
> @@ -4327,6 +4370,12 @@
> 'throttle': 'BlockdevOptionsThrottle',
> 'vdi': 'BlockdevOptionsGenericFormat',
> 'vhdx': 'BlockdevOptionsGenericFormat',
> + 'virtio-blk-vhost-user':
> + { 'type': 'BlockdevOptionsVirtioBlkVhostUser',
> + 'if': 'CONFIG_BLKIO' },
> + 'virtio-blk-vhost-vdpa':
> + { 'type': 'BlockdevOptionsVirtioBlkVhostVdpa',
> + 'if': 'CONFIG_BLKIO' },
> 'vmdk': 'BlockdevOptionsGenericCOWFormat',
> 'vpc': 'BlockdevOptionsGenericFormat',
> 'vvfat': 'BlockdevOptionsVVFAT'
[...]
Since the naming mess is not a new one made by this patch,
Acked-by: Markus Armbruster <armbru@redhat.com>
^ permalink raw reply [flat|nested] 23+ messages in thread
* Re: [RFC v4 11/11] virtio-blk: use BDRV_REQ_REGISTERED_BUF optimization hint
2022-08-25 7:43 ` David Hildenbrand
@ 2022-08-30 20:16 ` Stefan Hajnoczi
2022-09-02 8:06 ` David Hildenbrand
0 siblings, 1 reply; 23+ messages in thread
From: Stefan Hajnoczi @ 2022-08-30 20:16 UTC (permalink / raw)
To: David Hildenbrand
Cc: qemu-devel, Paolo Bonzini, Denis V. Lunev, Peter Xu, Yanan Wang,
Marcel Apfelbaum, Richard W.M. Jones, qemu-block, John Snow,
integration, Vladimir Sementsov-Ogievskiy,
Vladimir Sementsov-Ogievskiy, Laurent Vivier, Markus Armbruster,
Raphael Norwitz, Richard Henderson, Fam Zheng, sgarzare,
Alberto Faria, Kevin Wolf, Wen Congyang, Eric Blake, Hanna Reitz,
Philippe Mathieu-Daudé,
Eduardo Habkost, Michael S. Tsirkin, Thomas Huth, Jeff Cody,
Xie Changlong
[-- Attachment #1: Type: text/plain, Size: 3886 bytes --]
On Thu, Aug 25, 2022 at 09:43:16AM +0200, David Hildenbrand wrote:
> On 23.08.22 21:22, Stefan Hajnoczi wrote:
> > On Tue, Aug 23, 2022 at 10:01:59AM +0200, David Hildenbrand wrote:
> >> On 23.08.22 00:24, Stefan Hajnoczi wrote:
> >>> Register guest RAM using BlockRAMRegistrar and set the
> >>> BDRV_REQ_REGISTERED_BUF flag so block drivers can optimize memory
> >>> accesses in I/O requests.
> >>>
> >>> This is for vdpa-blk, vhost-user-blk, and other I/O interfaces that rely
> >>> on DMA mapping/unmapping.
> >>
> >> Can you explain why we're monitoring RAMRegistrar to hook into "guest
> >> RAM" and not go the usual path of the MemoryListener?
> >
> > The requirements are similar to VFIO, which uses RAMBlockNotifier. We
>
> Only VFIO NVME uses RAMBlockNotifier. Ordinary VFIO uses the MemoryListener.
>
> Maybe the difference is that ordinary VFIO has to replicate the actual
> guest physical memory layout, and VFIO NVME is only interested in
> possible guest RAM inside guest physical memory.
>
> > need to learn about all guest RAM because that's where I/O buffers are
> > located.
> >
> > Do you think RAMBlockNotifier should be avoided?
>
> I assume it depends on the use case. For saying "this might be used for
> I/O" it might be good enough I guess.
>
> >
> >> What will BDRV_REQ_REGISTERED_BUF actually do? Pin all guest memory in
> >> the worst case such as io_uring fixed buffers would do ( I hope not ).
> >
> > BLK_REQ_REGISTERED_BUF is a hint that no bounce buffer is necessary
> > because the I/O buffer is located in memory that was previously
> > registered with bdrv_registered_buf().
> >
> > The RAMBlockNotifier calls bdrv_register_buf() to let the libblkio
> > driver know about RAM. Some libblkio drivers ignore this hint, io_uring
> > may use the fixed buffers feature, vhost-user sends the shared memory
> > file descriptors to the vhost device server, and VFIO/vhost may pin
> > pages.
> >
> > So the blkio block driver doesn't add anything new, it's the union of
> > VFIO/vhost/vhost-user/etc memory requirements.
>
> The issue is if that backend pins memory inside any of these regions.
> Then, you're instantly incompatible to anything the relies on sparse
> RAMBlocks, such as memory ballooning or virtio-mem, and have to properly
> fence it.
>
> In that case, you'd have to successfully trigger
> ram_block_discard_disable(true) first, before pinning. Who would do that
> now conditionally, just like e.g., VFIO does?
>
> io_uring fixed buffers would be one such example that pins memory and is
> problematic. vfio (unless on s390x) is another example, as you point out.
Okay, I think libblkio needs to expose a bool property called
"mem-regions-pinned" so QEMU whether or not the registered buffers will
be pinned.
Then the QEMU BlockDriver can do:
if (mem_regions_pinned) {
if (ram_block_discard_disable(true) < 0) {
...fail to open block device...
}
}
Does that sound right?
Is "pinned" the best word to describe this or is there a more general
characteristic we are looking for?
>
> This has to be treated with care. Another thing to consider is that
> different backends might only support a limited number of such regions.
> I assume there is a way for QEMU to query this limit upfront? It might
> be required for memory hot(un)plug to figure out how many memory slots
> we actually have (for ordinary DIMMs, and if we ever want to make this
> compatible to virtio-mem, it might be required as well when the backend
> pins memory).
Yes, libblkio reports the maximum number of blkio_mem_regions supported
by the device. The property is called "max-mem-regions".
The QEMU BlockDriver currently doesn't use this information. Are there
any QEMU APIs that should be called to propagate this value?
Stefan
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^ permalink raw reply [flat|nested] 23+ messages in thread
* Re: [RFC v4 01/11] blkio: add libblkio block driver
2022-08-30 7:30 ` Markus Armbruster
@ 2022-08-30 20:18 ` Stefan Hajnoczi
0 siblings, 0 replies; 23+ messages in thread
From: Stefan Hajnoczi @ 2022-08-30 20:18 UTC (permalink / raw)
To: Markus Armbruster
Cc: qemu-devel, Paolo Bonzini, Denis V. Lunev, Peter Xu, Yanan Wang,
Marcel Apfelbaum, Richard W.M. Jones, qemu-block, John Snow,
integration, Vladimir Sementsov-Ogievskiy,
Vladimir Sementsov-Ogievskiy, David Hildenbrand, Laurent Vivier,
Raphael Norwitz, Richard Henderson, Fam Zheng, sgarzare,
Alberto Faria, Kevin Wolf, Wen Congyang, Eric Blake, Hanna Reitz,
Philippe Mathieu-Daudé,
Eduardo Habkost, Michael S. Tsirkin, Thomas Huth, Jeff Cody,
Xie Changlong
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On Tue, Aug 30, 2022 at 09:30:16AM +0200, Markus Armbruster wrote:
> Stefan Hajnoczi <stefanha@redhat.com> writes:
>
> > libblkio (https://gitlab.com/libblkio/libblkio/) is a library for
> > high-performance disk I/O. It currently supports io_uring,
> > virtio-blk-vhost-user, and virtio-blk-vhost-vdpa with additional drivers
> > under development.
> >
> > One of the reasons for developing libblkio is that other applications
> > besides QEMU can use it. This will be particularly useful for
> > virtio-blk-vhost-user which applications may wish to use for connecting
> > to qemu-storage-daemon.
> >
> > libblkio also gives us an opportunity to develop in Rust behind a C API
> > that is easy to consume from QEMU.
> >
> > This commit adds io_uring, virtio-blk-vhost-user, and
> > virtio-blk-vhost-vdpa BlockDrivers to QEMU using libblkio. It will be
> > easy to add other libblkio drivers since they will share the majority of
> > code.
> >
> > For now I/O buffers are copied through bounce buffers if the libblkio
> > driver requires it. Later commits add an optimization for
> > pre-registering guest RAM to avoid bounce buffers.
> >
> > The syntax is:
> >
> > --blockdev io_uring,node-name=drive0,filename=test.img,readonly=on|off,cache.direct=on|off
> >
> > and:
> >
> > --blockdev virtio-blk-vhost-vdpa,node-name=drive0,path=/dev/vdpa...,readonly=on|off
> >
> > Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> > ---
> > MAINTAINERS | 6 +
> > meson_options.txt | 2 +
> > qapi/block-core.json | 53 ++-
> > meson.build | 9 +
> > block/blkio.c | 725 ++++++++++++++++++++++++++++++++++
> > tests/qtest/modules-test.c | 3 +
> > block/meson.build | 1 +
> > scripts/meson-buildoptions.sh | 3 +
> > 8 files changed, 800 insertions(+), 2 deletions(-)
> > create mode 100644 block/blkio.c
> >
> > diff --git a/MAINTAINERS b/MAINTAINERS
> > index 5ce4227ff6..f8ccd5954c 100644
> > --- a/MAINTAINERS
> > +++ b/MAINTAINERS
> > @@ -3397,6 +3397,12 @@ L: qemu-block@nongnu.org
> > S: Maintained
> > F: block/vdi.c
> >
> > +blkio
> > +M: Stefan Hajnoczi <stefanha@redhat.com>
> > +L: qemu-block@nongnu.org
> > +S: Maintained
> > +F: block/blkio.c
> > +
> > iSCSI
> > M: Ronnie Sahlberg <ronniesahlberg@gmail.com>
> > M: Paolo Bonzini <pbonzini@redhat.com>
> > diff --git a/meson_options.txt b/meson_options.txt
> > index e58e158396..67d841a8d2 100644
> > --- a/meson_options.txt
> > +++ b/meson_options.txt
> > @@ -117,6 +117,8 @@ option('bzip2', type : 'feature', value : 'auto',
> > description: 'bzip2 support for DMG images')
> > option('cap_ng', type : 'feature', value : 'auto',
> > description: 'cap_ng support')
> > +option('blkio', type : 'feature', value : 'auto',
> > + description: 'libblkio block device driver')
> > option('bpf', type : 'feature', value : 'auto',
> > description: 'eBPF support')
> > option('cocoa', type : 'feature', value : 'auto',
> > diff --git a/qapi/block-core.json b/qapi/block-core.json
> > index 2173e7734a..c8d217b50c 100644
> > --- a/qapi/block-core.json
> > +++ b/qapi/block-core.json
> > @@ -2951,11 +2951,16 @@
> > 'file', 'snapshot-access', 'ftp', 'ftps', 'gluster',
> > {'name': 'host_cdrom', 'if': 'HAVE_HOST_BLOCK_DEVICE' },
> > {'name': 'host_device', 'if': 'HAVE_HOST_BLOCK_DEVICE' },
> > - 'http', 'https', 'iscsi',
> > + 'http', 'https',
> > + { 'name': 'io_uring', 'if': 'CONFIG_BLKIO' },
> > + 'iscsi',
> > 'luks', 'nbd', 'nfs', 'null-aio', 'null-co', 'nvme', 'parallels',
> > 'preallocate', 'qcow', 'qcow2', 'qed', 'quorum', 'raw', 'rbd',
> > { 'name': 'replication', 'if': 'CONFIG_REPLICATION' },
> > - 'ssh', 'throttle', 'vdi', 'vhdx', 'vmdk', 'vpc', 'vvfat' ] }
> > + 'ssh', 'throttle', 'vdi', 'vhdx',
> > + { 'name': 'virtio-blk-vhost-user', 'if': 'CONFIG_BLKIO' },
> > + { 'name': 'virtio-blk-vhost-vdpa', 'if': 'CONFIG_BLKIO' },
> > + 'vmdk', 'vpc', 'vvfat' ] }
> >
> > ##
> > # @BlockdevOptionsFile:
> > @@ -3678,6 +3683,42 @@
> > '*debug': 'int',
> > '*logfile': 'str' } }
> >
> > +##
> > +# @BlockdevOptionsIoUring:
> > +#
> > +# Driver specific block device options for the io_uring backend.
> > +#
> > +# @filename: path to the image file
> > +#
> > +# Since: 7.2
> > +##
> > +{ 'struct': 'BlockdevOptionsIoUring',
> > + 'data': { 'filename': 'str' } }
> > +
> > +##
> > +# @BlockdevOptionsVirtioBlkVhostUser:
> > +#
> > +# Driver specific block device options for the virtio-blk-vhost-user backend.
> > +#
> > +# @path: path to the vhost-user UNIX domain socket.
> > +#
> > +# Since: 7.2
> > +##
> > +{ 'struct': 'BlockdevOptionsVirtioBlkVhostUser',
> > + 'data': { 'path': 'str' } }
> > +
> > +##
> > +# @BlockdevOptionsVirtioBlkVhostVdpa:
> > +#
> > +# Driver specific block device options for the virtio-blk-vhost-vdpa backend.
> > +#
> > +# @path: path to the vhost-vdpa character device.
> > +#
> > +# Since: 7.2
> > +##
> > +{ 'struct': 'BlockdevOptionsVirtioBlkVhostVdpa',
> > + 'data': { 'path': 'str' } }
> > +
>
> We seem to be evenly split between 'filename' and 'path'. Before the
> patch we have four uses of 'filename' in this schema file (ImageInfo,
> ImageCheck, BlockDriverOptionsFile, BlockdevCreateOptionsFile), and
> three of 'path' (BlockdevOptionsSsh, BlockdevOptionsGluster,
> BlockdevOptionsNfs). There's also 'backing-file', 'data-file',
> 'backing-filename', 'file', and probably more (I stopped looking).
>
> I dislike 'path'. For what it's worth, POSIX calls this "pathname", and
> the components "filename". Everyday use hardly ever distinguishes
> between the two. Plain "path", however, is commonly used for lists of
> directories.
Yes :/
Stefan
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^ permalink raw reply [flat|nested] 23+ messages in thread
* Re: [RFC v4 00/11] blkio: add libblkio BlockDriver
2022-08-23 17:31 ` [RFC v4 00/11] blkio: add libblkio BlockDriver Vladimir Sementsov-Ogievskiy
2022-08-23 20:35 ` Stefan Hajnoczi
@ 2022-08-31 19:44 ` Stefan Hajnoczi
1 sibling, 0 replies; 23+ messages in thread
From: Stefan Hajnoczi @ 2022-08-31 19:44 UTC (permalink / raw)
To: Vladimir Sementsov-Ogievskiy
Cc: qemu-devel, Paolo Bonzini, Denis V. Lunev, Peter Xu, Yanan Wang,
Marcel Apfelbaum, Richard W.M. Jones, qemu-block, John Snow,
integration, Vladimir Sementsov-Ogievskiy, David Hildenbrand,
Laurent Vivier, Markus Armbruster, Raphael Norwitz,
Richard Henderson, Fam Zheng, sgarzare, Alberto Faria,
Kevin Wolf, Wen Congyang, Eric Blake, Hanna Reitz,
Philippe Mathieu-Daudé,
Eduardo Habkost, Michael S. Tsirkin, Thomas Huth, Jeff Cody,
Xie Changlong
[-- Attachment #1: Type: text/plain, Size: 1255 bytes --]
On Tue, Aug 23, 2022 at 08:31:03PM +0300, Vladimir Sementsov-Ogievskiy wrote:
> On 8/23/22 01:23, Stefan Hajnoczi wrote:
> > The remainder of the patch series reworks the existing QEMU bdrv_register_buf()
> > API so virtio-blk emulation efficiently map guest RAM for libblkio - some
> > libblkio drivers require that I/O buffer memory is pre-registered (think VFIO,
> > vhost, etc).
>
> Hi!
>
> So patches 01-11 are for performance optimization? Don't you have some performance measurements for it?
Hi Vladimir,
I ran the patches against qemu-storage-daemon's vhost-user-blk export
with iodepth=1 bs=512 to see the per-request overhead due to bounce
buffer allocation/mapping:
Name IOPS Error
bounce-buf 4373.81 ± 0.01%
registered-buf 13062.80 ± 0.67%
The BDRV_REQ_REGISTERED_BUF optimization version is about 3x faster.
Note that IOPS is low because the vhost-user-blk vq is not passed
through to the guest yet (Stefano is working on this). The guest is
also using interrupts, not polling (recent Linux virtio_blk.ko drivers
support poll queues).
I'll also include performance results in the next revision of the patch
series.
Stefan
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^ permalink raw reply [flat|nested] 23+ messages in thread
* Re: [RFC v4 11/11] virtio-blk: use BDRV_REQ_REGISTERED_BUF optimization hint
2022-08-30 20:16 ` Stefan Hajnoczi
@ 2022-09-02 8:06 ` David Hildenbrand
2022-09-05 20:50 ` Stefan Hajnoczi
0 siblings, 1 reply; 23+ messages in thread
From: David Hildenbrand @ 2022-09-02 8:06 UTC (permalink / raw)
To: Stefan Hajnoczi
Cc: qemu-devel, Paolo Bonzini, Denis V. Lunev, Peter Xu, Yanan Wang,
Marcel Apfelbaum, Richard W.M. Jones, qemu-block, John Snow,
integration, Vladimir Sementsov-Ogievskiy,
Vladimir Sementsov-Ogievskiy, Laurent Vivier, Markus Armbruster,
Raphael Norwitz, Richard Henderson, Fam Zheng, sgarzare,
Alberto Faria, Kevin Wolf, Wen Congyang, Eric Blake, Hanna Reitz,
Philippe Mathieu-Daudé,
Eduardo Habkost, Michael S. Tsirkin, Thomas Huth, Jeff Cody,
Xie Changlong
On 30.08.22 22:16, Stefan Hajnoczi wrote:
> On Thu, Aug 25, 2022 at 09:43:16AM +0200, David Hildenbrand wrote:
>> On 23.08.22 21:22, Stefan Hajnoczi wrote:
>>> On Tue, Aug 23, 2022 at 10:01:59AM +0200, David Hildenbrand wrote:
>>>> On 23.08.22 00:24, Stefan Hajnoczi wrote:
>>>>> Register guest RAM using BlockRAMRegistrar and set the
>>>>> BDRV_REQ_REGISTERED_BUF flag so block drivers can optimize memory
>>>>> accesses in I/O requests.
>>>>>
>>>>> This is for vdpa-blk, vhost-user-blk, and other I/O interfaces that rely
>>>>> on DMA mapping/unmapping.
>>>>
>>>> Can you explain why we're monitoring RAMRegistrar to hook into "guest
>>>> RAM" and not go the usual path of the MemoryListener?
>>>
>>> The requirements are similar to VFIO, which uses RAMBlockNotifier. We
>>
>> Only VFIO NVME uses RAMBlockNotifier. Ordinary VFIO uses the MemoryListener.
>>
>> Maybe the difference is that ordinary VFIO has to replicate the actual
>> guest physical memory layout, and VFIO NVME is only interested in
>> possible guest RAM inside guest physical memory.
>>
>>> need to learn about all guest RAM because that's where I/O buffers are
>>> located.
>>>
>>> Do you think RAMBlockNotifier should be avoided?
>>
>> I assume it depends on the use case. For saying "this might be used for
>> I/O" it might be good enough I guess.
>>
>>>
>>>> What will BDRV_REQ_REGISTERED_BUF actually do? Pin all guest memory in
>>>> the worst case such as io_uring fixed buffers would do ( I hope not ).
>>>
>>> BLK_REQ_REGISTERED_BUF is a hint that no bounce buffer is necessary
>>> because the I/O buffer is located in memory that was previously
>>> registered with bdrv_registered_buf().
>>>
>>> The RAMBlockNotifier calls bdrv_register_buf() to let the libblkio
>>> driver know about RAM. Some libblkio drivers ignore this hint, io_uring
>>> may use the fixed buffers feature, vhost-user sends the shared memory
>>> file descriptors to the vhost device server, and VFIO/vhost may pin
>>> pages.
>>>
>>> So the blkio block driver doesn't add anything new, it's the union of
>>> VFIO/vhost/vhost-user/etc memory requirements.
>>
>> The issue is if that backend pins memory inside any of these regions.
>> Then, you're instantly incompatible to anything the relies on sparse
>> RAMBlocks, such as memory ballooning or virtio-mem, and have to properly
>> fence it.
>>
>> In that case, you'd have to successfully trigger
>> ram_block_discard_disable(true) first, before pinning. Who would do that
>> now conditionally, just like e.g., VFIO does?
>>
>> io_uring fixed buffers would be one such example that pins memory and is
>> problematic. vfio (unless on s390x) is another example, as you point out.
>
> Okay, I think libblkio needs to expose a bool property called
> "mem-regions-pinned" so QEMU whether or not the registered buffers will
> be pinned.
>
> Then the QEMU BlockDriver can do:
>
> if (mem_regions_pinned) {
> if (ram_block_discard_disable(true) < 0) {
> ...fail to open block device...
> }
> }
>
> Does that sound right?
Yes, I think so.
>
> Is "pinned" the best word to describe this or is there a more general
> characteristic we are looking for?
pinning should be the right term. We want to express that all user page
tables will immediately get populated and that a kernel subsystem will
take longterm references on mapped page that will go out of sync as soon
as we discard memory e.g., using madvise(MADV_DONTEED).
We just should not confuse it with memlock / locking into memory, which
are yet different semantics (e.g., don't swap it out).
>
>>
>> This has to be treated with care. Another thing to consider is that
>> different backends might only support a limited number of such regions.
>> I assume there is a way for QEMU to query this limit upfront? It might
>> be required for memory hot(un)plug to figure out how many memory slots
>> we actually have (for ordinary DIMMs, and if we ever want to make this
>> compatible to virtio-mem, it might be required as well when the backend
>> pins memory).
>
> Yes, libblkio reports the maximum number of blkio_mem_regions supported
> by the device. The property is called "max-mem-regions".
>
> The QEMU BlockDriver currently doesn't use this information. Are there
> any QEMU APIs that should be called to propagate this value?
I assume we have to do exactly the same thing as e.g.,
vhost_has_free_slot()/kvm_has_free_slot() does.
Especially, hw/mem/memory-device.c needs care and
slots_limit/used_memslots handling in hw/virtio/vhost.c might be
relevant as well.
Note that I have some patches pending that extend that handling, by also
providing how many used+free slots there are, such as:
https://lore.kernel.org/all/20211027124531.57561-3-david@redhat.com/
--
Thanks,
David / dhildenb
^ permalink raw reply [flat|nested] 23+ messages in thread
* Re: [RFC v4 11/11] virtio-blk: use BDRV_REQ_REGISTERED_BUF optimization hint
2022-09-02 8:06 ` David Hildenbrand
@ 2022-09-05 20:50 ` Stefan Hajnoczi
0 siblings, 0 replies; 23+ messages in thread
From: Stefan Hajnoczi @ 2022-09-05 20:50 UTC (permalink / raw)
To: David Hildenbrand
Cc: qemu-devel, Paolo Bonzini, Denis V. Lunev, Peter Xu, Yanan Wang,
Marcel Apfelbaum, Richard W.M. Jones, qemu-block, John Snow,
integration, Vladimir Sementsov-Ogievskiy,
Vladimir Sementsov-Ogievskiy, Laurent Vivier, Markus Armbruster,
Raphael Norwitz, Richard Henderson, Fam Zheng, sgarzare,
Alberto Faria, Kevin Wolf, Wen Congyang, Eric Blake, Hanna Reitz,
Philippe Mathieu-Daudé,
Eduardo Habkost, Michael S. Tsirkin, Thomas Huth, Jeff Cody,
Xie Changlong
[-- Attachment #1: Type: text/plain, Size: 5283 bytes --]
On Fri, Sep 02, 2022 at 10:06:45AM +0200, David Hildenbrand wrote:
> On 30.08.22 22:16, Stefan Hajnoczi wrote:
> > On Thu, Aug 25, 2022 at 09:43:16AM +0200, David Hildenbrand wrote:
> >> On 23.08.22 21:22, Stefan Hajnoczi wrote:
> >>> On Tue, Aug 23, 2022 at 10:01:59AM +0200, David Hildenbrand wrote:
> >>>> On 23.08.22 00:24, Stefan Hajnoczi wrote:
> >>>>> Register guest RAM using BlockRAMRegistrar and set the
> >>>>> BDRV_REQ_REGISTERED_BUF flag so block drivers can optimize memory
> >>>>> accesses in I/O requests.
> >>>>>
> >>>>> This is for vdpa-blk, vhost-user-blk, and other I/O interfaces that rely
> >>>>> on DMA mapping/unmapping.
> >>>>
> >>>> Can you explain why we're monitoring RAMRegistrar to hook into "guest
> >>>> RAM" and not go the usual path of the MemoryListener?
> >>>
> >>> The requirements are similar to VFIO, which uses RAMBlockNotifier. We
> >>
> >> Only VFIO NVME uses RAMBlockNotifier. Ordinary VFIO uses the MemoryListener.
> >>
> >> Maybe the difference is that ordinary VFIO has to replicate the actual
> >> guest physical memory layout, and VFIO NVME is only interested in
> >> possible guest RAM inside guest physical memory.
> >>
> >>> need to learn about all guest RAM because that's where I/O buffers are
> >>> located.
> >>>
> >>> Do you think RAMBlockNotifier should be avoided?
> >>
> >> I assume it depends on the use case. For saying "this might be used for
> >> I/O" it might be good enough I guess.
> >>
> >>>
> >>>> What will BDRV_REQ_REGISTERED_BUF actually do? Pin all guest memory in
> >>>> the worst case such as io_uring fixed buffers would do ( I hope not ).
> >>>
> >>> BLK_REQ_REGISTERED_BUF is a hint that no bounce buffer is necessary
> >>> because the I/O buffer is located in memory that was previously
> >>> registered with bdrv_registered_buf().
> >>>
> >>> The RAMBlockNotifier calls bdrv_register_buf() to let the libblkio
> >>> driver know about RAM. Some libblkio drivers ignore this hint, io_uring
> >>> may use the fixed buffers feature, vhost-user sends the shared memory
> >>> file descriptors to the vhost device server, and VFIO/vhost may pin
> >>> pages.
> >>>
> >>> So the blkio block driver doesn't add anything new, it's the union of
> >>> VFIO/vhost/vhost-user/etc memory requirements.
> >>
> >> The issue is if that backend pins memory inside any of these regions.
> >> Then, you're instantly incompatible to anything the relies on sparse
> >> RAMBlocks, such as memory ballooning or virtio-mem, and have to properly
> >> fence it.
> >>
> >> In that case, you'd have to successfully trigger
> >> ram_block_discard_disable(true) first, before pinning. Who would do that
> >> now conditionally, just like e.g., VFIO does?
> >>
> >> io_uring fixed buffers would be one such example that pins memory and is
> >> problematic. vfio (unless on s390x) is another example, as you point out.
> >
> > Okay, I think libblkio needs to expose a bool property called
> > "mem-regions-pinned" so QEMU whether or not the registered buffers will
> > be pinned.
> >
> > Then the QEMU BlockDriver can do:
> >
> > if (mem_regions_pinned) {
> > if (ram_block_discard_disable(true) < 0) {
> > ...fail to open block device...
> > }
> > }
> >
> > Does that sound right?
>
> Yes, I think so.
>
> >
> > Is "pinned" the best word to describe this or is there a more general
> > characteristic we are looking for?
>
> pinning should be the right term. We want to express that all user page
> tables will immediately get populated and that a kernel subsystem will
> take longterm references on mapped page that will go out of sync as soon
> as we discard memory e.g., using madvise(MADV_DONTEED).
>
> We just should not confuse it with memlock / locking into memory, which
> are yet different semantics (e.g., don't swap it out).
>
> >
> >>
> >> This has to be treated with care. Another thing to consider is that
> >> different backends might only support a limited number of such regions.
> >> I assume there is a way for QEMU to query this limit upfront? It might
> >> be required for memory hot(un)plug to figure out how many memory slots
> >> we actually have (for ordinary DIMMs, and if we ever want to make this
> >> compatible to virtio-mem, it might be required as well when the backend
> >> pins memory).
> >
> > Yes, libblkio reports the maximum number of blkio_mem_regions supported
> > by the device. The property is called "max-mem-regions".
> >
> > The QEMU BlockDriver currently doesn't use this information. Are there
> > any QEMU APIs that should be called to propagate this value?
>
> I assume we have to do exactly the same thing as e.g.,
> vhost_has_free_slot()/kvm_has_free_slot() does.
>
> Especially, hw/mem/memory-device.c needs care and
> slots_limit/used_memslots handling in hw/virtio/vhost.c might be
> relevant as well.
>
>
> Note that I have some patches pending that extend that handling, by also
> providing how many used+free slots there are, such as:
>
> https://lore.kernel.org/all/20211027124531.57561-3-david@redhat.com/
Okay, thanks for explaining. I will make the libblkio driver participate
in free slots accounting.
Stefan
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^ permalink raw reply [flat|nested] 23+ messages in thread
end of thread, other threads:[~2022-09-05 20:51 UTC | newest]
Thread overview: 23+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2022-08-22 22:23 [RFC v4 00/11] blkio: add libblkio BlockDriver Stefan Hajnoczi
2022-08-22 22:23 ` [RFC v4 01/11] blkio: add libblkio block driver Stefan Hajnoczi
2022-08-30 7:30 ` Markus Armbruster
2022-08-30 20:18 ` Stefan Hajnoczi
2022-08-22 22:23 ` [RFC v4 02/11] numa: call ->ram_block_removed() in ram_block_notifer_remove() Stefan Hajnoczi
2022-08-22 22:23 ` [RFC v4 03/11] block: pass size to bdrv_unregister_buf() Stefan Hajnoczi
2022-08-22 22:23 ` [RFC v4 04/11] block: use BdrvRequestFlags type for supported flag fields Stefan Hajnoczi
2022-08-22 22:23 ` [RFC v4 05/11] block: add BDRV_REQ_REGISTERED_BUF request flag Stefan Hajnoczi
2022-08-22 22:23 ` [RFC v4 06/11] block: return errors from bdrv_register_buf() Stefan Hajnoczi
2022-08-22 22:23 ` [RFC v4 07/11] block: add BlockRAMRegistrar Stefan Hajnoczi
2022-08-22 22:23 ` [RFC v4 08/11] exec/cpu-common: add qemu_ram_get_fd() Stefan Hajnoczi
2022-08-22 22:24 ` [RFC v4 09/11] stubs: add qemu_ram_block_from_host() and qemu_ram_get_fd() Stefan Hajnoczi
2022-08-22 22:24 ` [RFC v4 10/11] blkio: implement BDRV_REQ_REGISTERED_BUF optimization Stefan Hajnoczi
2022-08-22 22:24 ` [RFC v4 11/11] virtio-blk: use BDRV_REQ_REGISTERED_BUF optimization hint Stefan Hajnoczi
2022-08-23 8:01 ` David Hildenbrand
2022-08-23 19:22 ` Stefan Hajnoczi
2022-08-25 7:43 ` David Hildenbrand
2022-08-30 20:16 ` Stefan Hajnoczi
2022-09-02 8:06 ` David Hildenbrand
2022-09-05 20:50 ` Stefan Hajnoczi
2022-08-23 17:31 ` [RFC v4 00/11] blkio: add libblkio BlockDriver Vladimir Sementsov-Ogievskiy
2022-08-23 20:35 ` Stefan Hajnoczi
2022-08-31 19:44 ` Stefan Hajnoczi
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