netdev - Re: [PATCH] vhost: Fix vhost_copy_to

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Date:   Wed, 11 Apr 2018 16:51:32 +0300
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     Eric Auger <eric.auger@...hat.com>
Cc:     eric.auger.pro@...il.com, linux-kernel@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
        kvm@...r.kernel.org, jasowang@...hat.com,
        kvmarm@...ts.cs.columbia.edu, stefanha@...hat.com
Subject: Re: [PATCH] vhost: Fix vhost_copy_to_user()

On Wed, Apr 11, 2018 at 03:30:38PM +0200, Eric Auger wrote:
> vhost_copy_to_user is used to copy vring used elements to userspace.
> We should use VHOST_ADDR_USED instead of VHOST_ADDR_DESC.
> 
> Fixes: f88949138058 ("vhost: introduce O(1) vq metadata cache")
> Signed-off-by: Eric Auger <eric.auger@...hat.com>

Acked-by: Michael S. Tsirkin <mst@...hat.com>

> ---
> 
> This fixes a stall observed when running an aarch64 guest with
> virtual smmu
> ---
>  drivers/vhost/vhost.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
> index bec722e..f44aead 100644
> --- a/drivers/vhost/vhost.c
> +++ b/drivers/vhost/vhost.c
> @@ -744,7 +744,7 @@ static int vhost_copy_to_user(struct vhost_virtqueue *vq, void __user *to,
>  		struct iov_iter t;
>  		void __user *uaddr = vhost_vq_meta_fetch(vq,
>  				     (u64)(uintptr_t)to, size,
> -				     VHOST_ADDR_DESC);
> +				     VHOST_ADDR_USED);
>  
>  		if (uaddr)
>  			return __copy_to_user(uaddr, from, size);
> -- 
> 2.5.5