[Qemu-devel] [PATCH 0/3] final patches for cache=writeback

[Qemu-devel] [PATCH 0/3] final patches for cache=writeback

[Paolo Bonzini]

Kevin,

here is a resend of the virtio-blk patches plus the one-liner for
flipping the default cache mode from writethrough to writeback.

Paolo Bonzini (3):
  virtio-blk: support VIRTIO_BLK_F_CONFIG_WCE
  virtio-blk: disable write cache if not negotiated
  blockdev: flip default cache mode from writethrough to writeback

 blockdev.c      |  1 +
 hw/virtio-blk.c | 30 ++++++++++++++++++++++++++++--
 hw/virtio-blk.h |  4 +++-
 3 file modificati, 32 inserzioni(+), 3 rimozioni(-)

-- 
1.7.11.2

[Qemu-devel] [PATCH 1/3] virtio-blk: support VIRTIO_BLK_F_CONFIG_WCE

[Paolo Bonzini]

Also rename VIRTIO_BLK_F_WCACHE to VIRTIO_BLK_F_WCE for consistency with
the spec.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 hw/virtio-blk.c | 16 ++++++++++++++--
 hw/virtio-blk.h |  4 +++-
 2 file modificati, 17 inserzioni(+), 3 rimozioni(-)

diff --git a/hw/virtio-blk.c b/hw/virtio-blk.c
index f21757e..9c12b61 100644
--- a/hw/virtio-blk.c
+++ b/hw/virtio-blk.c
@@ -509,9 +509,19 @@ static void virtio_blk_update_config(VirtIODevice *vdev, uint8_t *config)
     blkcfg.size_max = 0;
     blkcfg.physical_block_exp = get_physical_block_exp(s->conf);
     blkcfg.alignment_offset = 0;
+    blkcfg.wce = bdrv_enable_write_cache(s->bs);
     memcpy(config, &blkcfg, sizeof(struct virtio_blk_config));
 }
 
+static void virtio_blk_set_config(VirtIODevice *vdev, const uint8_t *config)
+{
+    VirtIOBlock *s = to_virtio_blk(vdev);
+    struct virtio_blk_config blkcfg;
+
+    memcpy(&blkcfg, config, sizeof(blkcfg));
+    bdrv_set_enable_write_cache(s->bs, blkcfg.wce != 0);
+}
+
 static uint32_t virtio_blk_get_features(VirtIODevice *vdev, uint32_t features)
 {
     VirtIOBlock *s = to_virtio_blk(vdev);
@@ -522,9 +532,10 @@ static uint32_t virtio_blk_get_features(VirtIODevice *vdev, uint32_t features)
     features |= (1 << VIRTIO_BLK_F_BLK_SIZE);
     features |= (1 << VIRTIO_BLK_F_SCSI);
 
+    features |= (1 << VIRTIO_BLK_F_CONFIG_WCE);
     if (bdrv_enable_write_cache(s->bs))
-        features |= (1 << VIRTIO_BLK_F_WCACHE);
-    
+        features |= (1 << VIRTIO_BLK_F_WCE);
+
     if (bdrv_is_read_only(s->bs))
         features |= 1 << VIRTIO_BLK_F_RO;
 
@@ -609,6 +620,7 @@ VirtIODevice *virtio_blk_init(DeviceState *dev, VirtIOBlkConf *blk)
                                           sizeof(VirtIOBlock));
 
     s->vdev.get_config = virtio_blk_update_config;
+    s->vdev.set_config = virtio_blk_set_config;
     s->vdev.get_features = virtio_blk_get_features;
     s->vdev.reset = virtio_blk_reset;
     s->bs = blk->conf.bs;
diff --git a/hw/virtio-blk.h b/hw/virtio-blk.h
index 79ebccc..35834cf 100644
--- a/hw/virtio-blk.h
+++ b/hw/virtio-blk.h
@@ -31,8 +31,9 @@
 #define VIRTIO_BLK_F_BLK_SIZE   6       /* Block size of disk is available*/
 #define VIRTIO_BLK_F_SCSI       7       /* Supports scsi command passthru */
 /* #define VIRTIO_BLK_F_IDENTIFY   8       ATA IDENTIFY supported, DEPRECATED */
-#define VIRTIO_BLK_F_WCACHE     9       /* write cache enabled */
+#define VIRTIO_BLK_F_WCE        9       /* write cache enabled */
 #define VIRTIO_BLK_F_TOPOLOGY   10      /* Topology information is available */
+#define VIRTIO_BLK_F_CONFIG_WCE 11      /* write cache configurable */
 
 #define VIRTIO_BLK_ID_BYTES     20      /* ID string length */
 
@@ -49,6 +50,7 @@ struct virtio_blk_config
     uint8_t alignment_offset;
     uint16_t min_io_size;
     uint32_t opt_io_size;
+    uint8_t wce;
 } QEMU_PACKED;
 
 /* These two define direction. */
-- 
1.7.11.2

[Qemu-devel] [PATCH 2/3] virtio-blk: disable write cache if not negotiated

[Paolo Bonzini]

If the guest does not support flushes, we should run in writethrough mode.
The setting is temporary until the next reset, so that for example the
BIOS will run in writethrough mode while Linux will run with a writeback
cache.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 hw/virtio-blk.c | 14 ++++++++++++++
 1 file modificato, 14 inserzioni(+)

diff --git a/hw/virtio-blk.c b/hw/virtio-blk.c
index 9c12b61..36bfb12 100644
--- a/hw/virtio-blk.c
+++ b/hw/virtio-blk.c
@@ -542,6 +542,19 @@ static uint32_t virtio_blk_get_features(VirtIODevice *vdev, uint32_t features)
     return features;
 }
 
+static void virtio_blk_set_status(VirtIODevice *vdev, uint8_t status)
+{
+    VirtIOBlock *s = to_virtio_blk(vdev);
+    uint32_t features;
+
+    if (!(status & VIRTIO_CONFIG_S_DRIVER_OK)) {
+        return;
+    }
+
+    features = vdev->guest_features;
+    bdrv_set_enable_write_cache(s->bs, !!(features & (1 << VIRTIO_BLK_F_WCE)));
+}
+
 static void virtio_blk_save(QEMUFile *f, void *opaque)
 {
     VirtIOBlock *s = opaque;
@@ -622,6 +635,7 @@ VirtIODevice *virtio_blk_init(DeviceState *dev, VirtIOBlkConf *blk)
     s->vdev.get_config = virtio_blk_update_config;
     s->vdev.set_config = virtio_blk_set_config;
     s->vdev.get_features = virtio_blk_get_features;
+    s->vdev.set_status = virtio_blk_set_status;
     s->vdev.reset = virtio_blk_reset;
     s->bs = blk->conf.bs;
     s->conf = &blk->conf;
-- 
1.7.11.2

[Qemu-devel] [PATCH 3/3] blockdev: flip default cache mode from writethrough to writeback

[Paolo Bonzini]

Now all major device models (IDE, SCSI, virtio) can choose between
writethrough and writeback at run-time, and virtio will even revert
to writethrough if the guest is not capable of sending flushes.  So
we can change the default to writeback at last.

Tested, for lack of a better idea, with a breakpoint on bdrv_open
and all cache choices one by one.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 blockdev.c | 1 +
 1 file modificato, 1 inserzione(+)

diff --git a/blockdev.c b/blockdev.c
index 8669142..7c83baa 100644
--- a/blockdev.c
+++ b/blockdev.c
@@ -377,6 +377,7 @@ DriveInfo *drive_init(QemuOpts *opts, int default_to_scsi)
 	}
     }
 
+    bdrv_flags |= BDRV_O_CACHE_WB;
     if ((buf = qemu_opt_get(opts, "cache")) != NULL) {
         if (bdrv_parse_cache_flags(buf, &bdrv_flags) != 0) {
             error_report("invalid cache option");
-- 
1.7.11.2

Re: [Qemu-devel] [PATCH 0/3] final patches for cache=writeback

[Kevin Wolf]

Am 09.08.2012 16:07, schrieb Paolo Bonzini:
> Kevin,
> 
> here is a resend of the virtio-blk patches plus the one-liner for
> flipping the default cache mode from writethrough to writeback.
> 
> Paolo Bonzini (3):
>   virtio-blk: support VIRTIO_BLK_F_CONFIG_WCE
>   virtio-blk: disable write cache if not negotiated
>   blockdev: flip default cache mode from writethrough to writeback
> 
>  blockdev.c      |  1 +
>  hw/virtio-blk.c | 30 ++++++++++++++++++++++++++++--
>  hw/virtio-blk.h |  4 +++-
>  3 file modificati, 32 inserzioni(+), 3 rimozioni(-)

Thanks, applied all to the block branch.

Kevin