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

[Jason Wang]

On 2018年10月11日 22:08, w...@redhat.com wrote:

From: Wei Xu <w...@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 <w...@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 */