Re: [PATCH] vhost: reduce stack usage in log_used

[Jason Wang]

On 2020/9/15 上午2:08, Li Wang wrote:

Fix the warning: [-Werror=-Wframe-larger-than=]

drivers/vhost/vhost.c: In function log_used:
drivers/vhost/vhost.c:1906:1:
warning: the frame size of 1040 bytes is larger than 1024 bytes

Signed-off-by: Li Wang 
---
  drivers/vhost/vhost.c | 2 +-
  drivers/vhost/vhost.h | 1 +
  2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index b45519c..31837a5
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -1884,7 +1884,7 @@ static int log_write_hva(struct vhost_virtqueue *vq, u64 
hva, u64 len)
  
  static int log_used(struct vhost_virtqueue *vq, u64 used_offset, u64 len)

  {
-   struct iovec iov[64];
+   struct iovec *iov = vq->log_iov;
int i, ret;
  
  	if (!vq->iotlb)

diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
index 9032d3c..5fe4b47
--- a/drivers/vhost/vhost.h
+++ b/drivers/vhost/vhost.h
@@ -123,6 +123,7 @@ struct vhost_virtqueue {
/* Log write descriptors */
void __user *log_base;
struct vhost_log *log;
+   struct iovec log_iov[64];
  
  	/* Ring endianness. Defaults to legacy native endianness.

 * Set to true when starting a modern virtio device. */



Acked-by: Jason Wang 


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Re: [PATCH] vhost: reduce stack usage in log_used

[Jason Wang]

- Original Message -
> Fix the warning: [-Werror=-Wframe-larger-than=]
> 
> drivers/vhost/vhost.c: In function log_used:
> drivers/vhost/vhost.c:1906:1:
> warning: the frame size of 1040 bytes is larger than 1024 bytes
> 
> Signed-off-by: Li Wang 
> ---
>  drivers/vhost/vhost.c | 14 ++
>  1 file changed, 10 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
> index b45519c..41769de 100644
> --- a/drivers/vhost/vhost.c
> +++ b/drivers/vhost/vhost.c
> @@ -1884,25 +1884,31 @@ static int log_write_hva(struct vhost_virtqueue *vq,
> u64 hva, u64 len)
>  
>  static int log_used(struct vhost_virtqueue *vq, u64 used_offset, u64 len)
>  {
> - struct iovec iov[64];
> + struct iovec *iov;
>   int i, ret;
>  
>   if (!vq->iotlb)
>   return log_write(vq->log_base, vq->log_addr + used_offset, len);
>  
> + iov = kcalloc(64, sizeof(*iov), GFP_KERNEL);
> + if (!iov)
> + return -ENOMEM;

Let's preallocate it in e.g vhost_net_open().

We don't want to fail the log due to -ENOMEM.

Thanks

> +
>   ret = translate_desc(vq, (uintptr_t)vq->used + used_offset,
>len, iov, 64, VHOST_ACCESS_WO);
>   if (ret < 0)
> - return ret;
> + goto out;
>  
>   for (i = 0; i < ret; i++) {
>   ret = log_write_hva(vq, (uintptr_t)iov[i].iov_base,
>   iov[i].iov_len);
>   if (ret)
> - return ret;
> + goto out;
>   }
>  
> - return 0;
> +out:
> + kfree(iov);
> + return ret;
>  }
>  
>  int vhost_log_write(struct vhost_virtqueue *vq, struct vhost_log *log,
> --
> 2.7.4
> 
> 

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