From e460991883d7209d52d0fdb534d9cd8cce0f9cce Mon Sep 17 00:00:00 2001 From: Alberto Faria Date: Fri, 2 May 2025 13:11:14 +0100 Subject: [PATCH 1/5] scsi-disk: Add native FUA write support Simply propagate the FUA flag on write requests to the driver. The block layer will emulate it if necessary. Signed-off-by: Alberto Faria Message-ID: <20250502121115.3613717-2-afaria@redhat.com> Reviewed-by: Kevin Wolf Signed-off-by: Kevin Wolf --- hw/scsi/scsi-disk.c | 53 +++++++++++++-------------------------------- 1 file changed, 15 insertions(+), 38 deletions(-) diff --git a/hw/scsi/scsi-disk.c b/hw/scsi/scsi-disk.c index cb4af1b715..738d8df8ec 100644 --- a/hw/scsi/scsi-disk.c +++ b/hw/scsi/scsi-disk.c @@ -74,7 +74,7 @@ struct SCSIDiskClass { */ DMAIOFunc *dma_readv; DMAIOFunc *dma_writev; - bool (*need_fua_emulation)(SCSICommand *cmd); + bool (*need_fua)(SCSICommand *cmd); void (*update_sense)(SCSIRequest *r); }; @@ -85,7 +85,7 @@ typedef struct SCSIDiskReq { uint32_t sector_count; uint32_t buflen; bool started; - bool need_fua_emulation; + bool need_fua; struct iovec iov; QEMUIOVector qiov; BlockAcctCookie acct; @@ -389,24 +389,6 @@ static bool scsi_is_cmd_fua(SCSICommand *cmd) } } -static void scsi_write_do_fua(SCSIDiskReq *r) -{ - SCSIDiskState *s = DO_UPCAST(SCSIDiskState, qdev, r->req.dev); - - assert(r->req.aiocb == NULL); - assert(!r->req.io_canceled); - - if (r->need_fua_emulation) { - block_acct_start(blk_get_stats(s->qdev.conf.blk), &r->acct, 0, - BLOCK_ACCT_FLUSH); - r->req.aiocb = blk_aio_flush(s->qdev.conf.blk, scsi_aio_complete, r); - return; - } - - scsi_req_complete(&r->req, GOOD); - scsi_req_unref(&r->req); -} - static void scsi_dma_complete_noio(SCSIDiskReq *r, int ret) { assert(r->req.aiocb == NULL); @@ -416,12 +398,7 @@ static void scsi_dma_complete_noio(SCSIDiskReq *r, int ret) r->sector += r->sector_count; r->sector_count = 0; - if (r->req.cmd.mode == SCSI_XFER_TO_DEV) { - scsi_write_do_fua(r); - return; - } else { - scsi_req_complete(&r->req, GOOD); - } + scsi_req_complete(&r->req, GOOD); done: scsi_req_unref(&r->req); @@ -564,7 +541,7 @@ static void scsi_read_data(SCSIRequest *req) first = !r->started; r->started = true; - if (first && r->need_fua_emulation) { + if (first && r->need_fua) { block_acct_start(blk_get_stats(s->qdev.conf.blk), &r->acct, 0, BLOCK_ACCT_FLUSH); r->req.aiocb = blk_aio_flush(s->qdev.conf.blk, scsi_do_read_cb, r); @@ -589,8 +566,7 @@ static void scsi_write_complete_noio(SCSIDiskReq *r, int ret) r->sector += n; r->sector_count -= n; if (r->sector_count == 0) { - scsi_write_do_fua(r); - return; + scsi_req_complete(&r->req, GOOD); } else { scsi_init_iovec(r, SCSI_DMA_BUF_SIZE); trace_scsi_disk_write_complete_noio(r->req.tag, r->qiov.size); @@ -623,6 +599,7 @@ static void scsi_write_data(SCSIRequest *req) SCSIDiskReq *r = DO_UPCAST(SCSIDiskReq, req, req); SCSIDiskState *s = DO_UPCAST(SCSIDiskState, qdev, r->req.dev); SCSIDiskClass *sdc = (SCSIDiskClass *) object_get_class(OBJECT(s)); + BlockCompletionFunc *cb; /* No data transfer may already be in progress */ assert(r->req.aiocb == NULL); @@ -648,11 +625,10 @@ static void scsi_write_data(SCSIRequest *req) if (r->req.cmd.buf[0] == VERIFY_10 || r->req.cmd.buf[0] == VERIFY_12 || r->req.cmd.buf[0] == VERIFY_16) { - if (r->req.sg) { - scsi_dma_complete_noio(r, 0); - } else { - scsi_write_complete_noio(r, 0); - } + block_acct_start(blk_get_stats(s->qdev.conf.blk), &r->acct, 0, + BLOCK_ACCT_FLUSH); + cb = r->req.sg ? scsi_dma_complete : scsi_write_complete; + r->req.aiocb = blk_aio_flush(s->qdev.conf.blk, cb, r); return; } @@ -2391,7 +2367,7 @@ static int32_t scsi_disk_dma_command(SCSIRequest *req, uint8_t *buf) scsi_check_condition(r, SENSE_CODE(LBA_OUT_OF_RANGE)); return 0; } - r->need_fua_emulation = sdc->need_fua_emulation(&r->req.cmd); + r->need_fua = sdc->need_fua(&r->req.cmd); if (r->sector_count == 0) { scsi_req_complete(&r->req, GOOD); } @@ -3137,7 +3113,8 @@ BlockAIOCB *scsi_dma_writev(int64_t offset, QEMUIOVector *iov, { SCSIDiskReq *r = opaque; SCSIDiskState *s = DO_UPCAST(SCSIDiskState, qdev, r->req.dev); - return blk_aio_pwritev(s->qdev.conf.blk, offset, iov, 0, cb, cb_opaque); + int flags = r->need_fua ? BDRV_REQ_FUA : 0; + return blk_aio_pwritev(s->qdev.conf.blk, offset, iov, flags, cb, cb_opaque); } static char *scsi_property_get_loadparm(Object *obj, Error **errp) @@ -3186,7 +3163,7 @@ static void scsi_disk_base_class_initfn(ObjectClass *klass, const void *data) device_class_set_legacy_reset(dc, scsi_disk_reset); sdc->dma_readv = scsi_dma_readv; sdc->dma_writev = scsi_dma_writev; - sdc->need_fua_emulation = scsi_is_cmd_fua; + sdc->need_fua = scsi_is_cmd_fua; } static const TypeInfo scsi_disk_base_info = { @@ -3338,7 +3315,7 @@ static void scsi_block_class_initfn(ObjectClass *klass, const void *data) sdc->dma_readv = scsi_block_dma_readv; sdc->dma_writev = scsi_block_dma_writev; sdc->update_sense = scsi_block_update_sense; - sdc->need_fua_emulation = scsi_block_no_fua; + sdc->need_fua = scsi_block_no_fua; dc->desc = "SCSI block device passthrough"; device_class_set_props(dc, scsi_block_properties); dc->vmsd = &vmstate_scsi_disk_state; From 5562e214e82ae4bcb0b642cc52b304bdc78a58c3 Mon Sep 17 00:00:00 2001 From: Alberto Faria Date: Fri, 2 May 2025 13:11:15 +0100 Subject: [PATCH 2/5] scsi-disk: Advertise FUA support by default Allow the guest to submit FUA requests directly, instead of forcing it to emulate them using a regular flush. Signed-off-by: Alberto Faria Message-ID: <20250502121115.3613717-3-afaria@redhat.com> Reviewed-by: Kevin Wolf Signed-off-by: Kevin Wolf --- hw/core/machine.c | 4 +++- hw/scsi/scsi-disk.c | 2 +- 2 files changed, 4 insertions(+), 2 deletions(-) diff --git a/hw/core/machine.c b/hw/core/machine.c index b8ae155dfa..c3f3a5020d 100644 --- a/hw/core/machine.c +++ b/hw/core/machine.c @@ -37,7 +37,9 @@ #include "hw/virtio/virtio-iommu.h" #include "audio/audio.h" -GlobalProperty hw_compat_10_0[] = {}; +GlobalProperty hw_compat_10_0[] = { + { "scsi-hd", "dpofua", "off" }, +}; const size_t hw_compat_10_0_len = G_N_ELEMENTS(hw_compat_10_0); GlobalProperty hw_compat_9_2[] = { diff --git a/hw/scsi/scsi-disk.c b/hw/scsi/scsi-disk.c index 738d8df8ec..b4782c6248 100644 --- a/hw/scsi/scsi-disk.c +++ b/hw/scsi/scsi-disk.c @@ -3192,7 +3192,7 @@ static const Property scsi_hd_properties[] = { DEFINE_PROP_BIT("removable", SCSIDiskState, features, SCSI_DISK_F_REMOVABLE, false), DEFINE_PROP_BIT("dpofua", SCSIDiskState, features, - SCSI_DISK_F_DPOFUA, false), + SCSI_DISK_F_DPOFUA, true), DEFINE_PROP_UINT64("wwn", SCSIDiskState, qdev.wwn, 0), DEFINE_PROP_UINT64("port_wwn", SCSIDiskState, qdev.port_wwn, 0), DEFINE_PROP_UINT16("port_index", SCSIDiskState, port_index, 0), From ff2ab634e4bb3bddcf5f5ee29e0b46f71e3f4b54 Mon Sep 17 00:00:00 2001 From: Denis Rastyogin Date: Tue, 6 May 2025 17:13:37 +0300 Subject: [PATCH 3/5] qemu-img: fix offset calculation in bench This error was discovered by fuzzing qemu-img. The current offset calculation leads to an EIO error in block/block-backend.c: blk_check_byte_request(): if (offset > len || len - offset < bytes) { return -EIO; } This triggers the error message: "qemu-img: Failed request: Input/output error". Example of the issue: offset: 260076 len: 260096 bytes: 4096 This fix ensures that offset remains within a valid range. Signed-off-by: Denis Rastyogin Message-ID: <20250506141410.100119-1-gerben@altlinux.org> [kwolf: Fixed up integer overflow] Signed-off-by: Kevin Wolf --- qemu-img.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/qemu-img.c b/qemu-img.c index 76ac5d3028..139eeb5039 100644 --- a/qemu-img.c +++ b/qemu-img.c @@ -4488,10 +4488,10 @@ static void bench_cb(void *opaque, int ret) */ b->in_flight++; b->offset += b->step; - if (b->image_size == 0) { + if (b->image_size <= b->bufsize) { b->offset = 0; } else { - b->offset %= b->image_size; + b->offset %= b->image_size - b->bufsize; } if (b->write) { acb = blk_aio_pwritev(b->blk, offset, b->qiov, 0, bench_cb, b); From 5634622bcb339f213469eceeff005640492fc902 Mon Sep 17 00:00:00 2001 From: Stefan Hajnoczi Date: Thu, 17 Apr 2025 17:10:53 -0400 Subject: [PATCH 4/5] file-posix: allow BLKZEROOUT with -t writeback The Linux BLKZEROOUT ioctl is only invoked when BDRV_O_NOCACHE is set because old kernels did not invalidate the page cache. In that case mixing BLKZEROOUT with buffered I/O could lead to corruption. However, Linux 4.9 commit 22dd6d356628 ("block: invalidate the page cache when issuing BLKZEROOUT") made BLKZEROOUT coherent with the page cache. I have checked that Linux 4.9+ kernels are shipped at least as far back as Debian 10 (buster), openSUSE Leap 15.2, and RHEL/CentOS 8. Use BLKZEROOUT with buffered I/O, mostly so `qemu-img ... -t writeback` can offload write zeroes. Cc: Paolo Bonzini Cc: Christoph Hellwig Signed-off-by: Stefan Hajnoczi Message-ID: <20250417211053.98700-1-stefanha@redhat.com> Reviewed-by: Eric Blake Reviewed-by: Kevin Wolf Signed-off-by: Kevin Wolf --- block/file-posix.c | 11 ----------- 1 file changed, 11 deletions(-) diff --git a/block/file-posix.c b/block/file-posix.c index ec95b74869..5a3532e40b 100644 --- a/block/file-posix.c +++ b/block/file-posix.c @@ -785,17 +785,6 @@ static int raw_open_common(BlockDriverState *bs, QDict *options, } #endif - if (S_ISBLK(st.st_mode)) { -#ifdef __linux__ - /* On Linux 3.10, BLKDISCARD leaves stale data in the page cache. Do - * not rely on the contents of discarded blocks unless using O_DIRECT. - * Same for BLKZEROOUT. - */ - if (!(bs->open_flags & BDRV_O_NOCACHE)) { - s->has_write_zeroes = false; - } -#endif - } #ifdef __FreeBSD__ if (S_ISCHR(st.st_mode)) { /* From bf627788ef17721955bfcfba84209a07ae5f54ea Mon Sep 17 00:00:00 2001 From: Kevin Wolf Date: Thu, 22 May 2025 15:08:03 +0200 Subject: [PATCH 5/5] file-posix: Probe paths and retry SG_IO on potential path errors When scsi-block is used on a host multipath device, it runs into the problem that the kernel dm-mpath doesn't know anything about SCSI or SG_IO and therefore can't decide if a SG_IO request returned an error and needs to be retried on a different path. Instead of getting working failover, an error is returned to scsi-block and handled according to the configured error policy. Obviously, this is not what users want, they want working failover. QEMU can parse the SG_IO result and determine whether this could have been a path error, but just retrying the same request could just send it to the same failing path again and result in the same error. With a kernel that supports the DM_MPATH_PROBE_PATHS ioctl on dm-mpath block devices (queued in the device mapper tree for Linux 6.16), we can tell the kernel to probe all paths and tell us if any usable paths remained. If so, we can now retry the SG_IO ioctl and expect it to be sent to a working path. Signed-off-by: Kevin Wolf Message-ID: <20250522130803.34738-1-kwolf@redhat.com> Reviewed-by: Stefan Hajnoczi Reviewed-by: Hanna Czenczek Signed-off-by: Kevin Wolf --- block/file-posix.c | 115 ++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 114 insertions(+), 1 deletion(-) diff --git a/block/file-posix.c b/block/file-posix.c index 5a3532e40b..9b5f08ccb2 100644 --- a/block/file-posix.c +++ b/block/file-posix.c @@ -41,6 +41,7 @@ #include "scsi/pr-manager.h" #include "scsi/constants.h" +#include "scsi/utils.h" #if defined(__APPLE__) && (__MACH__) #include @@ -72,6 +73,7 @@ #include #endif #include +#include #include #include #include @@ -138,6 +140,22 @@ #define RAW_LOCK_PERM_BASE 100 #define RAW_LOCK_SHARED_BASE 200 +/* + * Multiple retries are mostly meant for two separate scenarios: + * + * - DM_MPATH_PROBE_PATHS returns success, but before SG_IO completes, another + * path goes down. + * + * - DM_MPATH_PROBE_PATHS failed all paths in the current path group, so we have + * to send another SG_IO to switch to another path group to probe the paths in + * it. + * + * Even if each path is in a separate path group (path_grouping_policy set to + * failover), it's rare to have more than eight path groups - and even then + * pretty unlikely that only bad path groups would be chosen in eight retries. + */ +#define SG_IO_MAX_RETRIES 8 + typedef struct BDRVRawState { int fd; bool use_lock; @@ -165,6 +183,7 @@ typedef struct BDRVRawState { bool use_linux_aio:1; bool has_laio_fdsync:1; bool use_linux_io_uring:1; + bool use_mpath:1; int page_cache_inconsistent; /* errno from fdatasync failure */ bool has_fallocate; bool needs_alignment; @@ -4253,15 +4272,105 @@ hdev_open_Mac_error: /* Since this does ioctl the device must be already opened */ bs->sg = hdev_is_sg(bs); + /* sg devices aren't even block devices and can't use dm-mpath */ + s->use_mpath = !bs->sg; + return ret; } #if defined(__linux__) +#if defined(DM_MPATH_PROBE_PATHS) +static bool coroutine_fn sgio_path_error(int ret, sg_io_hdr_t *io_hdr) +{ + if (ret < 0) { + switch (ret) { + case -ENODEV: + return true; + case -EAGAIN: + /* + * The device is probably suspended. This happens while the dm table + * is reloaded, e.g. because a path is added or removed. This is an + * operation that should complete within 1ms, so just wait a bit and + * retry. + * + * If the device was suspended for another reason, we'll wait and + * retry SG_IO_MAX_RETRIES times. This is a tolerable delay before + * we return an error and potentially stop the VM. + */ + qemu_co_sleep_ns(QEMU_CLOCK_REALTIME, 1000000); + return true; + default: + return false; + } + } + + if (io_hdr->host_status != SCSI_HOST_OK) { + return true; + } + + switch (io_hdr->status) { + case GOOD: + case CONDITION_GOOD: + case INTERMEDIATE_GOOD: + case INTERMEDIATE_C_GOOD: + case RESERVATION_CONFLICT: + case COMMAND_TERMINATED: + return false; + case CHECK_CONDITION: + return !scsi_sense_buf_is_guest_recoverable(io_hdr->sbp, + io_hdr->mx_sb_len); + default: + return true; + } +} + +static bool coroutine_fn hdev_co_ioctl_sgio_retry(RawPosixAIOData *acb, int ret) +{ + BDRVRawState *s = acb->bs->opaque; + RawPosixAIOData probe_acb; + + if (!s->use_mpath) { + return false; + } + + if (!sgio_path_error(ret, acb->ioctl.buf)) { + return false; + } + + probe_acb = (RawPosixAIOData) { + .bs = acb->bs, + .aio_type = QEMU_AIO_IOCTL, + .aio_fildes = s->fd, + .aio_offset = 0, + .ioctl = { + .buf = NULL, + .cmd = DM_MPATH_PROBE_PATHS, + }, + }; + + ret = raw_thread_pool_submit(handle_aiocb_ioctl, &probe_acb); + if (ret == -ENOTTY) { + s->use_mpath = false; + } else if (ret == -EAGAIN) { + /* The device might be suspended for a table reload, worth retrying */ + return true; + } + + return ret == 0; +} +#else +static bool coroutine_fn hdev_co_ioctl_sgio_retry(RawPosixAIOData *acb, int ret) +{ + return false; +} +#endif /* DM_MPATH_PROBE_PATHS */ + static int coroutine_fn hdev_co_ioctl(BlockDriverState *bs, unsigned long int req, void *buf) { BDRVRawState *s = bs->opaque; RawPosixAIOData acb; + int retries = SG_IO_MAX_RETRIES; int ret; ret = fd_open(bs); @@ -4289,7 +4398,11 @@ hdev_co_ioctl(BlockDriverState *bs, unsigned long int req, void *buf) }, }; - return raw_thread_pool_submit(handle_aiocb_ioctl, &acb); + do { + ret = raw_thread_pool_submit(handle_aiocb_ioctl, &acb); + } while (req == SG_IO && retries-- && hdev_co_ioctl_sgio_retry(&acb, ret)); + + return ret; } #endif /* linux */