diff options
Diffstat (limited to 'hw/block/virtio-blk.c')
| -rw-r--r-- | hw/block/virtio-blk.c | 24 |
1 files changed, 22 insertions, 2 deletions
diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c index e2f55cc946..49a23c33f7 100644 --- a/hw/block/virtio-blk.c +++ b/hw/block/virtio-blk.c @@ -460,9 +460,9 @@ static void virtio_blk_dma_restart_cb(void *opaque, int running, static void virtio_blk_reset(VirtIODevice *vdev) { -#ifdef CONFIG_VIRTIO_BLK_DATA_PLANE VirtIOBlock *s = VIRTIO_BLK(vdev); +#ifdef CONFIG_VIRTIO_BLK_DATA_PLANE if (s->dataplane) { virtio_blk_data_plane_stop(s->dataplane); } @@ -473,6 +473,7 @@ static void virtio_blk_reset(VirtIODevice *vdev) * are per-device request lists. */ bdrv_drain_all(); + bdrv_set_enable_write_cache(s->bs, s->original_wce); } /* coalesce internal state, copy to pci i/o region 0 @@ -564,7 +565,25 @@ static void virtio_blk_set_status(VirtIODevice *vdev, uint8_t status) } features = vdev->guest_features; - bdrv_set_enable_write_cache(s->bs, !!(features & (1 << VIRTIO_BLK_F_WCE))); + + /* A guest that supports VIRTIO_BLK_F_CONFIG_WCE must be able to send + * cache flushes. Thus, the "auto writethrough" behavior is never + * necessary for guests that support the VIRTIO_BLK_F_CONFIG_WCE feature. + * Leaving it enabled would break the following sequence: + * + * Guest started with "-drive cache=writethrough" + * Guest sets status to 0 + * Guest sets DRIVER bit in status field + * Guest reads host features (WCE=0, CONFIG_WCE=1) + * Guest writes guest features (WCE=0, CONFIG_WCE=1) + * Guest writes 1 to the WCE configuration field (writeback mode) + * Guest sets DRIVER_OK bit in status field + * + * s->bs would erroneously be placed in writethrough mode. + */ + if (!(features & (1 << VIRTIO_BLK_F_CONFIG_WCE))) { + bdrv_set_enable_write_cache(s->bs, !!(features & (1 << VIRTIO_BLK_F_WCE))); + } } static void virtio_blk_save(QEMUFile *f, void *opaque) @@ -674,6 +693,7 @@ static int virtio_blk_device_init(VirtIODevice *vdev) } blkconf_serial(&blk->conf, &blk->serial); + s->original_wce = bdrv_enable_write_cache(blk->conf.bs); if (blkconf_geometry(&blk->conf, NULL, 65535, 255, 255) < 0) { return -1; } |