RE: [PATCH] Netvsc: Call hv_unmap_memory() in the netvsc_device_remove()

[Haiyang Zhang]

> -----Original Message-----
> From: Tianyu Lan <ltykernel@xxxxxxxxx>
> Sent: Tuesday, February 1, 2022 11:32 AM
> To: KY Srinivasan <kys@xxxxxxxxxxxxx>; Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>; Stephen
> Hemminger <sthemmin@xxxxxxxxxxxxx>; wei.liu@xxxxxxxxxx; Dexuan Cui <decui@xxxxxxxxxxxxx>;
> tglx@xxxxxxxxxxxxx; mingo@xxxxxxxxxx; bp@xxxxxxxxx; dave.hansen@xxxxxxxxxxxxxxx;
> x86@xxxxxxxxxx; hpa@xxxxxxxxx; davem@xxxxxxxxxxxxx; kuba@xxxxxxxxxx; hch@xxxxxxxxxxxxx;
> m.szyprowski@xxxxxxxxxxx; robin.murphy@xxxxxxx; Michael Kelley (LINUX)
> <mikelley@xxxxxxxxxxxxx>
> Cc: Tianyu Lan <Tianyu.Lan@xxxxxxxxxxxxx>; iommu@xxxxxxxxxxxxxxxxxxxxxxxxxx; linux-
> hyperv@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; netdev@xxxxxxxxxxxxxxx
> Subject: [PATCH] Netvsc: Call hv_unmap_memory() in the netvsc_device_remove()
> 
> From: Tianyu Lan <Tianyu.Lan@xxxxxxxxxxxxx>
> 
> netvsc_device_remove() calls vunmap() inside which should not be
> called in the interrupt context. Current code calls hv_unmap_memory()
> in the free_netvsc_device() which is rcu callback and maybe called
> in the interrupt context. This will trigger BUG_ON(in_interrupt())
> in the vunmap(). Fix it via moving hv_unmap_memory() to netvsc_device_
> remove().
> 
> Fixes: 846da38de0e8 ("net: netvsc: Add Isolation VM support for netvsc driver")
> Signed-off-by: Tianyu Lan <Tianyu.Lan@xxxxxxxxxxxxx>
> ---
>  drivers/net/hyperv/netvsc.c | 18 ++++++++++--------
>  1 file changed, 10 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/net/hyperv/netvsc.c b/drivers/net/hyperv/netvsc.c
> index afa81a9480cc..f989f920d4ce 100644
> --- a/drivers/net/hyperv/netvsc.c
> +++ b/drivers/net/hyperv/netvsc.c
> @@ -154,19 +154,15 @@ static void free_netvsc_device(struct rcu_head *head)
> 
>  	kfree(nvdev->extension);
> 
> -	if (nvdev->recv_original_buf) {
> -		hv_unmap_memory(nvdev->recv_buf);
> +	if (nvdev->recv_original_buf)
>  		vfree(nvdev->recv_original_buf);
> -	} else {
> +	else
>  		vfree(nvdev->recv_buf);
> -	}
> 
> -	if (nvdev->send_original_buf) {
> -		hv_unmap_memory(nvdev->send_buf);
> +	if (nvdev->send_original_buf)
>  		vfree(nvdev->send_original_buf);
> -	} else {
> +	else
>  		vfree(nvdev->send_buf);
> -	}
> 
>  	bitmap_free(nvdev->send_section_map);
> 
> @@ -765,6 +761,12 @@ void netvsc_device_remove(struct hv_device *device)
>  		netvsc_teardown_send_gpadl(device, net_device, ndev);
>  	}
> 
> +	if (net_device->recv_original_buf)
> +		hv_unmap_memory(net_device->recv_buf);
> +
> +	if (net_device->send_original_buf)
> +		hv_unmap_memory(net_device->send_buf);
> +
>  	/* Release all resources */
>  	free_netvsc_device_rcu(net_device);
>  }

Reviewed-by: Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>