[net-next,1/3] vhost: generalize adding used elem
diff mbox series

Message ID 20181213101022.12475-2-jasowang@redhat.com
State Superseded
Headers show
Series
  • vhost: accelerate metadata access through vmap()
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Commit Message

Jason Wang Dec. 13, 2018, 10:10 a.m. UTC
Use one generic vhost_copy_to_user() instead of two dedicated
accessor. This will simplify the conversion to fine grain accessors.

Signed-off-by: Jason Wang <jasowang@redhat.com>
---
 drivers/vhost/vhost.c | 11 +----------
 1 file changed, 1 insertion(+), 10 deletions(-)

Comments

Michael S. Tsirkin Dec. 13, 2018, 7:41 p.m. UTC | #1
On Thu, Dec 13, 2018 at 06:10:20PM +0800, Jason Wang wrote:
> Use one generic vhost_copy_to_user() instead of two dedicated
> accessor. This will simplify the conversion to fine grain accessors.
> 
> Signed-off-by: Jason Wang <jasowang@redhat.com>


The reason we did it like this is because it was faster.
Want to try benchmarking before we change it?

> ---
>  drivers/vhost/vhost.c | 11 +----------
>  1 file changed, 1 insertion(+), 10 deletions(-)
> 
> diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
> index 3a5f81a66d34..1c54ec1b82f8 100644
> --- a/drivers/vhost/vhost.c
> +++ b/drivers/vhost/vhost.c
> @@ -2164,16 +2164,7 @@ static int __vhost_add_used_n(struct vhost_virtqueue *vq,
>  
>  	start = vq->last_used_idx & (vq->num - 1);
>  	used = vq->used->ring + start;
> -	if (count == 1) {
> -		if (vhost_put_user(vq, heads[0].id, &used->id)) {
> -			vq_err(vq, "Failed to write used id");
> -			return -EFAULT;
> -		}
> -		if (vhost_put_user(vq, heads[0].len, &used->len)) {
> -			vq_err(vq, "Failed to write used len");
> -			return -EFAULT;
> -		}
> -	} else if (vhost_copy_to_user(vq, used, heads, count * sizeof *used)) {
> +	if (vhost_copy_to_user(vq, used, heads, count * sizeof *used)) {
>  		vq_err(vq, "Failed to write used");
>  		return -EFAULT;
>  	}
> -- 
> 2.17.1
Jason Wang Dec. 14, 2018, 4 a.m. UTC | #2
On 2018/12/14 上午3:41, Michael S. Tsirkin wrote:
> On Thu, Dec 13, 2018 at 06:10:20PM +0800, Jason Wang wrote:
>> Use one generic vhost_copy_to_user() instead of two dedicated
>> accessor. This will simplify the conversion to fine grain accessors.
>>
>> Signed-off-by: Jason Wang <jasowang@redhat.com>
>
> The reason we did it like this is because it was faster.
> Want to try benchmarking before we change it?


Faster is a good side effect of such conversion. Otherwise we need two 
new fine grain memory accessor.

But, anyway, I can test its impact.

Thanks


>
>> ---
>>   drivers/vhost/vhost.c | 11 +----------
>>   1 file changed, 1 insertion(+), 10 deletions(-)
>>
>> diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
>> index 3a5f81a66d34..1c54ec1b82f8 100644
>> --- a/drivers/vhost/vhost.c
>> +++ b/drivers/vhost/vhost.c
>> @@ -2164,16 +2164,7 @@ static int __vhost_add_used_n(struct vhost_virtqueue *vq,
>>   
>>   	start = vq->last_used_idx & (vq->num - 1);
>>   	used = vq->used->ring + start;
>> -	if (count == 1) {
>> -		if (vhost_put_user(vq, heads[0].id, &used->id)) {
>> -			vq_err(vq, "Failed to write used id");
>> -			return -EFAULT;
>> -		}
>> -		if (vhost_put_user(vq, heads[0].len, &used->len)) {
>> -			vq_err(vq, "Failed to write used len");
>> -			return -EFAULT;
>> -		}
>> -	} else if (vhost_copy_to_user(vq, used, heads, count * sizeof *used)) {
>> +	if (vhost_copy_to_user(vq, used, heads, count * sizeof *used)) {
>>   		vq_err(vq, "Failed to write used");
>>   		return -EFAULT;
>>   	}
>> -- 
>> 2.17.1

Patch
diff mbox series

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 3a5f81a66d34..1c54ec1b82f8 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -2164,16 +2164,7 @@  static int __vhost_add_used_n(struct vhost_virtqueue *vq,
 
 	start = vq->last_used_idx & (vq->num - 1);
 	used = vq->used->ring + start;
-	if (count == 1) {
-		if (vhost_put_user(vq, heads[0].id, &used->id)) {
-			vq_err(vq, "Failed to write used id");
-			return -EFAULT;
-		}
-		if (vhost_put_user(vq, heads[0].len, &used->len)) {
-			vq_err(vq, "Failed to write used len");
-			return -EFAULT;
-		}
-	} else if (vhost_copy_to_user(vq, used, heads, count * sizeof *used)) {
+	if (vhost_copy_to_user(vq, used, heads, count * sizeof *used)) {
 		vq_err(vq, "Failed to write used");
 		return -EFAULT;
 	}