Introduce "struct vring_packed".
Modify VhostShadowVirtqueue so it can support split and packed virtqueue
formats.
Signed-off-by: Sahil Siddiq <sahilcdq@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.
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);
--
2.48.1On Mon, Mar 24, 2025 at 3:00 PM Sahil Siddiq <icegambit91@gmail.com> wrote:
>
> Introduce "struct vring_packed".
>
> Modify VhostShadowVirtqueue so it can support split and packed virtqueue
> formats.
>
> Signed-off-by: Sahil Siddiq <sahilcdq@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?
> 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
>
Hi,
On 3/26/25 4:56 PM, Eugenio Perez Martin wrote:
> On Mon, Mar 24, 2025 at 3:00 PM Sahil Siddiq <icegambit91@gmail.com> wrote:
>>
>> Introduce "struct vring_packed".
>>
>> Modify VhostShadowVirtqueue so it can support split and packed virtqueue
>> formats.
>>
>> Signed-off-by: Sahil Siddiq <sahilcdq@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
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