Hi,
On 3/26/25 4:56 PM, Eugenio Perez Martin wrote:
On Mon, Mar 24, 2025 at 3:00 PM Sahil Siddiq <icegambi...@gmail.com> wrote:
Introduce "struct vring_packed".
Modify VhostShadowVirtqueue so it can support split and packed virtqueue
formats.
Signed-off-by: Sahil Siddiq <sahil...@proton.me>
---
Changes from v4 -> v5:
- This was commit #3 in v4. This has been reordered to commit #2
based on review comments.
- Place shadow_avail_idx, shadow_used_idx, last_used_idx
above the "shadow vring" union.
What is the reason for the member reorder?
In v1 [1], I had made the decision to shift all the fields in the structure that
are used by split and packed vqs above the "shadow vring" union. But I hadn't
moved shadow_avail_idx, shadow_used_idx or last_used_idx.
The latter two are also used by both vring formats. "shadow_avail_idx" is only
used by split vqs but I think it'll have to be used in packed vqs as well in the
future.
To keep things consistent I thought I would shift these fields as well.
Although,
these shifts shouldn't have an impact on the functionality. The shifts can be
dropped without issue.
hw/virtio/vhost-shadow-virtqueue.h | 87 +++++++++++++++++++-----------
1 file changed, 56 insertions(+), 31 deletions(-)
diff --git a/hw/virtio/vhost-shadow-virtqueue.h
b/hw/virtio/vhost-shadow-virtqueue.h
index 9c273739d6..5f7699da9d 100644
--- a/hw/virtio/vhost-shadow-virtqueue.h
+++ b/hw/virtio/vhost-shadow-virtqueue.h
@@ -46,10 +46,65 @@ typedef struct VhostShadowVirtqueueOps {
VirtQueueAvailCallback avail_handler;
} VhostShadowVirtqueueOps;
+struct vring_packed {
+ /* Actual memory layout for this queue. */
+ struct {
+ unsigned int num;
+ struct vring_packed_desc *desc;
+ struct vring_packed_desc_event *driver;
+ struct vring_packed_desc_event *device;
+ } vring;
+
+ /* Avail used flags. */
+ uint16_t avail_used_flags;
+
+ /* Index of the next avail descriptor. */
+ uint16_t next_avail_idx;
+
+ /* Driver ring wrap counter */
+ bool avail_wrap_counter;
+};
+
/* Shadow virtqueue to relay notifications */
typedef struct VhostShadowVirtqueue {
+ /* True if packed virtqueue */
+ bool is_packed;
+
+ /* Virtio queue shadowing */
+ VirtQueue *vq;
+
+ /* Virtio device */
+ VirtIODevice *vdev;
+
+ /* SVQ vring descriptors state */
+ SVQDescState *desc_state;
+
+ /*
+ * Backup next field for each descriptor so we can recover securely, not
+ * needing to trust the device access.
+ */
+ uint16_t *desc_next;
+
+ /* Next free descriptor */
+ uint16_t free_head;
+
+ /* Size of SVQ vring free descriptors */
+ uint16_t num_free;
+
+ /* Next head to expose to the device */
+ uint16_t shadow_avail_idx;
+
+ /* Last seen used idx */
+ uint16_t shadow_used_idx;
+
+ /* Next head to consume from the device */
+ uint16_t last_used_idx;
+
/* Shadow vring */
- struct vring vring;
+ union {
+ struct vring vring;
+ struct vring_packed vring_packed;
+ };
/* Shadow kick notifier, sent to vhost */
EventNotifier hdev_kick;
@@ -69,47 +124,17 @@ typedef struct VhostShadowVirtqueue {
/* Guest's call notifier, where the SVQ calls guest. */
EventNotifier svq_call;
- /* Virtio queue shadowing */
- VirtQueue *vq;
-
- /* Virtio device */
- VirtIODevice *vdev;
-
/* IOVA mapping */
VhostIOVATree *iova_tree;
- /* SVQ vring descriptors state */
- SVQDescState *desc_state;
-
/* Next VirtQueue element that guest made available */
VirtQueueElement *next_guest_avail_elem;
- /*
- * Backup next field for each descriptor so we can recover securely, not
- * needing to trust the device access.
- */
- uint16_t *desc_next;
-
/* Caller callbacks */
const VhostShadowVirtqueueOps *ops;
/* Caller callbacks opaque */
void *ops_opaque;
-
- /* Next head to expose to the device */
- uint16_t shadow_avail_idx;
-
- /* Next free descriptor */
- uint16_t free_head;
-
- /* Last seen used idx */
- uint16_t shadow_used_idx;
-
- /* Next head to consume from the device */
- uint16_t last_used_idx;
-
- /* Size of SVQ vring free descriptors */
- uint16_t num_free;
} VhostShadowVirtqueue;
bool vhost_svq_valid_features(uint64_t features, Error **errp);
--
2.48.1
Thanks,
Sahil
[1] https://lists.nongnu.org/archive/html/qemu-devel/2024-06/msg03417.html
