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virtio-blk: disable write cache if not negotiated 

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>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Paolo Bonzini 2012-08-09 16:07:20 +02:00 committed by Kevin Wolf
parent 13e3dce068
commit 9315cbfd8d
1 changed files with 14 additions and 0 deletions
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14
hw/virtio-blk.c
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@ -543,6 +543,19 @@ 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;
@ -623,6 +636,7 @@ 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;