[PATCH v3 0/2] scsi-disk: Add FUA write support

[PATCH v3 0/2] scsi-disk: Add FUA write support

[Alberto Faria]

Add scsi-disk support for Force Unit Access (FUA) writes. The first patch lets
us avoid FUA emulation when the underlying driver supports it natively. The
second patch makes scsi-disk devices advertise FUA support by default.

v3:
- Restore flush on VERIFY.
- Modify hw_compat_10_0 instead of hw_compat_9_2.

v2:
- Drop FUA write emulation logic since the block layer already does that.
- Add machine type compat for "dpofua".

Alberto Faria (2):
  scsi-disk: Add native FUA write support
  scsi-disk: Advertise FUA support by default

 hw/core/machine.c   |  4 +++-
 hw/scsi/scsi-disk.c | 55 +++++++++++++--------------------------------
 2 files changed, 19 insertions(+), 40 deletions(-)

-- 
2.49.0

[PATCH v3 1/2] scsi-disk: Add native FUA write support

[Alberto Faria]

Simply propagate the FUA flag on write requests to the driver. The block
layer will emulate it if necessary.

Signed-off-by: Alberto Faria <afaria@redhat.com>
---
 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;
-- 
2.49.0

[PATCH v3 2/2] scsi-disk: Advertise FUA support by default

[Alberto Faria]

Allow the guest to submit FUA requests directly, instead of forcing it
to emulate them using a regular flush.

Signed-off-by: Alberto Faria <afaria@redhat.com>
---
 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 ed01798d37..0e3d8c4065 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),
-- 
2.49.0

Re: [PATCH v3 0/2] scsi-disk: Add FUA write support

[Kevin Wolf]

Am 02.05.2025 um 14:11 hat Alberto Faria geschrieben:
> Add scsi-disk support for Force Unit Access (FUA) writes. The first patch lets
> us avoid FUA emulation when the underlying driver supports it natively. The
> second patch makes scsi-disk devices advertise FUA support by default.
> 
> v3:
> - Restore flush on VERIFY.
> - Modify hw_compat_10_0 instead of hw_compat_9_2.
> 
> v2:
> - Drop FUA write emulation logic since the block layer already does that.
> - Add machine type compat for "dpofua".
> 
> Alberto Faria (2):
>   scsi-disk: Add native FUA write support
>   scsi-disk: Advertise FUA support by default

Thanks, applied to the block branch.

Kevin