Re: [Qemu-devel] [[RFC v3 02/12] virtio: redefine structure & memory cache for packed ring

[Jason Wang <jasowang@redhat.com>]

On 2018年10月11日 22:08, wexu@redhat.com wrote:
> From: Wei Xu <wexu@redhat.com>
>
> Redefine packed ring structure according to qemu nomenclature,
> also supported data(event index, wrap counter, etc) are introduced.
>
> Signed-off-by: Wei Xu <wexu@redhat.com>
> ---
>   hw/virtio/virtio.c | 26 ++++++++++++++++++++++++--
>   1 file changed, 24 insertions(+), 2 deletions(-)
>
> diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
> index 94f5c8e..500eecf 100644
> --- a/hw/virtio/virtio.c
> +++ b/hw/virtio/virtio.c
> @@ -39,6 +39,13 @@ typedef struct VRingDesc
>       uint16_t next;
>   } VRingDesc;
>   
> +typedef struct VRingPackedDesc {
> +    uint64_t addr;
> +    uint32_t len;
> +    uint16_t id;
> +    uint16_t flags;
> +} VRingPackedDesc;
> +
>   typedef struct VRingAvail
>   {
>       uint16_t flags;
> @@ -62,8 +69,14 @@ typedef struct VRingUsed
>   typedef struct VRingMemoryRegionCaches {
>       struct rcu_head rcu;
>       MemoryRegionCache desc;
> -    MemoryRegionCache avail;
> -    MemoryRegionCache used;
> +    union {
> +        MemoryRegionCache avail;
> +        MemoryRegionCache driver;
> +    };

Can we reuse avail and used?

> +    union {
> +        MemoryRegionCache used;
> +        MemoryRegionCache device;
> +    };
>   } VRingMemoryRegionCaches;
>   
>   typedef struct VRing
> @@ -77,6 +90,11 @@ typedef struct VRing
>       VRingMemoryRegionCaches *caches;
>   } VRing;
>   
> +typedef struct VRingPackedDescEvent {
> +    uint16_t off_wrap;
> +    uint16_t flags;
> +} VRingPackedDescEvent ;
> +
>   struct VirtQueue
>   {
>       VRing vring;
> @@ -87,6 +105,10 @@ struct VirtQueue
>       /* Last avail_idx read from VQ. */
>       uint16_t shadow_avail_idx;
>   
> +    uint16_t event_idx;

Need a comment to explain this field.

Thanks

> +    bool event_wrap_counter;
> +    bool avail_wrap_counter;
> +
>       uint16_t used_idx;
>   
>       /* Last used index value we have signalled on */