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virtio: add feature checking helpers

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Add a helper function for checking whether a bit is set in the guest
features for a vdev as well as one that works on a feature bit set.

Convert code that open-coded this: It cleans up the code and makes it
easier to extend the guest feature bits.

Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
This commit is contained in:
Cornelia Huck 2014-12-11 14:25:06 +01:00 • committed by Michael S. Tsirkin
parent 0cd09c3a6c
commit ef546f1275
8 changed files with 42 additions and 31 deletions
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7
hw/block/virtio-blk.c
View file

@ -733,7 +733,6 @@ static uint32_t virtio_blk_get_features(VirtIODevice *vdev, uint32_t features)
static void virtio_blk_set_status(VirtIODevice *vdev, uint8_t status)
{
VirtIOBlock *s = VIRTIO_BLK(vdev);
uint32_t features;
if (s->dataplane && !(status & (VIRTIO_CONFIG_S_DRIVER |
VIRTIO_CONFIG_S_DRIVER_OK))) {
@ -744,8 +743,6 @@ static void virtio_blk_set_status(VirtIODevice *vdev, uint8_t status)
return;
}
features = vdev->guest_features;
/* 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.
@ -761,10 +758,10 @@ static void virtio_blk_set_status(VirtIODevice *vdev, uint8_t status)
*
* s->blk would erroneously be placed in writethrough mode.
*/
if (!(features & (1 << VIRTIO_BLK_F_CONFIG_WCE))) {
if (!virtio_has_feature(vdev, VIRTIO_BLK_F_CONFIG_WCE)) {
aio_context_acquire(blk_get_aio_context(s->blk));
blk_set_enable_write_cache(s->blk,
!!(features & (1 << VIRTIO_BLK_F_WCE)));
virtio_has_feature(vdev, VIRTIO_BLK_F_WCE));
aio_context_release(blk_get_aio_context(s->blk));
}
}