Re: [PATCH v2 2/4] vhost: Drop variable last_avail_idx in vhost_get_vq_desc()

2024-04-29 Thread Gavin Shan 

On 4/30/24 04:45, Michael S. Tsirkin wrote:

On Mon, Apr 29, 2024 at 08:13:58PM +1000, Gavin Shan wrote:

The local variable @last_avail_idx is equivalent to vq->last_avail_idx.
So the code can be simplified a bit by dropping the local variable
@last_avail_idx.

No functional change intended.

Signed-off-by: Gavin Shan 
---
  drivers/vhost/vhost.c | 7 +++
  1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 7aa623117aab..b278c0333a66 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -2524,7 +2524,6 @@ int vhost_get_vq_desc(struct vhost_virtqueue *vq,
  {
struct vring_desc desc;
unsigned int i, head, found = 0;
-   u16 last_avail_idx = vq->last_avail_idx;
__virtio16 ring_head;
int ret, access;
  
@@ -2539,10 +2538,10 @@ int vhost_get_vq_desc(struct vhost_virtqueue *vq,
  
  	/* Grab the next descriptor number they're advertising, and increment

 * the index we've seen. */
-   if (unlikely(vhost_get_avail_head(vq, _head, last_avail_idx))) {
+   if (unlikely(vhost_get_avail_head(vq, _head, vq->last_avail_idx))) 
{
vq_err(vq, "Failed to read head: idx %d address %p\n",
-  last_avail_idx,
-  >avail->ring[last_avail_idx % vq->num]);
+  vq->last_avail_idx,
+  >avail->ring[vq->last_avail_idx % vq->num]);
return -EFAULT;
}


I don't see the big advantage and the line is long now.



The point is to avoid the local variable @last_avail_idx since it's equivalent
to vq->last_avail_idx, as stated in the commit log. Besides, it paves the way
for PATCH[v2 3/4] where the whole logic fetching the head and sanity check is
moved to vhost_get_avail_head(), so that vhost_get_vq_desc() is simplified

I will drop PATCH[2, 3, 4] as you suggested.

Thanks,
Gavin

Re: [PATCH v2 2/4] vhost: Drop variable last_avail_idx in vhost_get_vq_desc()

2024-04-29 Thread Michael S. Tsirkin 
On Mon, Apr 29, 2024 at 08:13:58PM +1000, Gavin Shan wrote:
> The local variable @last_avail_idx is equivalent to vq->last_avail_idx.
> So the code can be simplified a bit by dropping the local variable
> @last_avail_idx.
> 
> No functional change intended.
> 
> Signed-off-by: Gavin Shan 
> ---
>  drivers/vhost/vhost.c | 7 +++
>  1 file changed, 3 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
> index 7aa623117aab..b278c0333a66 100644
> --- a/drivers/vhost/vhost.c
> +++ b/drivers/vhost/vhost.c
> @@ -2524,7 +2524,6 @@ int vhost_get_vq_desc(struct vhost_virtqueue *vq,
>  {
>   struct vring_desc desc;
>   unsigned int i, head, found = 0;
> - u16 last_avail_idx = vq->last_avail_idx;
>   __virtio16 ring_head;
>   int ret, access;
>  
> @@ -2539,10 +2538,10 @@ int vhost_get_vq_desc(struct vhost_virtqueue *vq,
>  
>   /* Grab the next descriptor number they're advertising, and increment
>* the index we've seen. */
> - if (unlikely(vhost_get_avail_head(vq, _head, last_avail_idx))) {
> + if (unlikely(vhost_get_avail_head(vq, _head, vq->last_avail_idx))) 
> {
>   vq_err(vq, "Failed to read head: idx %d address %p\n",
> -last_avail_idx,
> ->avail->ring[last_avail_idx % vq->num]);
> +vq->last_avail_idx,
> +>avail->ring[vq->last_avail_idx % vq->num]);
>   return -EFAULT;
>   }

I don't see the big advantage and the line is long now.

>  
> -- 
> 2.44.0

[PATCH v2 2/4] vhost: Drop variable last_avail_idx in vhost_get_vq_desc()

2024-04-29 Thread Gavin Shan 
The local variable @last_avail_idx is equivalent to vq->last_avail_idx.
So the code can be simplified a bit by dropping the local variable
@last_avail_idx.

No functional change intended.

Signed-off-by: Gavin Shan 
---
 drivers/vhost/vhost.c | 7 +++
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 7aa623117aab..b278c0333a66 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -2524,7 +2524,6 @@ int vhost_get_vq_desc(struct vhost_virtqueue *vq,
 {
struct vring_desc desc;
unsigned int i, head, found = 0;
-   u16 last_avail_idx = vq->last_avail_idx;
__virtio16 ring_head;
int ret, access;
 
@@ -2539,10 +2538,10 @@ int vhost_get_vq_desc(struct vhost_virtqueue *vq,
 
/* Grab the next descriptor number they're advertising, and increment
 * the index we've seen. */
-   if (unlikely(vhost_get_avail_head(vq, _head, last_avail_idx))) {
+   if (unlikely(vhost_get_avail_head(vq, _head, vq->last_avail_idx))) 
{
vq_err(vq, "Failed to read head: idx %d address %p\n",
-  last_avail_idx,
-  >avail->ring[last_avail_idx % vq->num]);
+  vq->last_avail_idx,
+  >avail->ring[vq->last_avail_idx % vq->num]);
return -EFAULT;
}
 
-- 
2.44.0