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From: "Michael S. Tsirkin" <mst@redhat.com>
To: Alvaro Karsz <alvaro.karsz@solid-run.com>
Cc: netdev@vger.kernel.org,
	Eugenio Perez Martin <eperezma@redhat.com>,
	kvm@vger.kernel.org, virtualization@lists.linux-foundation.org
Subject: Re: [PATCH] vhost-vdpa: print error when vhost_vdpa_alloc_domain fails
Date: Wed, 1 Feb 2023 10:52:35 -0500	[thread overview]
Message-ID: <20230201105200-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <20230201152018.1270226-1-alvaro.karsz@solid-run.com>

On Wed, Feb 01, 2023 at 05:20:18PM +0200, Alvaro Karsz wrote:
> Add a print explaining why vhost_vdpa_alloc_domain failed if the device
> is not IOMMU cache coherent capable.
> 
> Without this print, we have no hint why the operation failed.
> 
> For example:
> 
> $ virsh start <domain>
> 	error: Failed to start domain <domain>
> 	error: Unable to open '/dev/vhost-vdpa-<idx>' for vdpa device:
> 	       Unknown error 524
> 
> Suggested-by: Eugenio Perez Martin <eperezma@redhat.com>
> Signed-off-by: Alvaro Karsz <alvaro.karsz@solid-run.com>

I'm not sure this is a good idea. Userspace is not supposed to be
able to trigger dev_err.

> ---
>  drivers/vhost/vdpa.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
> index 23db92388393..56287506aa0d 100644
> --- a/drivers/vhost/vdpa.c
> +++ b/drivers/vhost/vdpa.c
> @@ -1151,8 +1151,11 @@ static int vhost_vdpa_alloc_domain(struct vhost_vdpa *v)
>  	if (!bus)
>  		return -EFAULT;
>  
> -	if (!device_iommu_capable(dma_dev, IOMMU_CAP_CACHE_COHERENCY))
> +	if (!device_iommu_capable(dma_dev, IOMMU_CAP_CACHE_COHERENCY)) {
> +		dev_err(&v->dev,
> +			"Failed to allocate domain, device is not IOMMU cache coherent capable\n");
>  		return -ENOTSUPP;
> +	}
>  
>  	v->domain = iommu_domain_alloc(bus);
>  	if (!v->domain)
> -- 
> 2.34.1

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WARNING: multiple messages have this Message-ID (diff)
From: "Michael S. Tsirkin" <mst@redhat.com>
To: Alvaro Karsz <alvaro.karsz@solid-run.com>
Cc: jasowang@redhat.com, virtualization@lists.linux-foundation.org,
	kvm@vger.kernel.org, netdev@vger.kernel.org,
	Eugenio Perez Martin <eperezma@redhat.com>
Subject: Re: [PATCH] vhost-vdpa: print error when vhost_vdpa_alloc_domain fails
Date: Wed, 1 Feb 2023 10:52:35 -0500	[thread overview]
Message-ID: <20230201105200-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <20230201152018.1270226-1-alvaro.karsz@solid-run.com>

On Wed, Feb 01, 2023 at 05:20:18PM +0200, Alvaro Karsz wrote:
> Add a print explaining why vhost_vdpa_alloc_domain failed if the device
> is not IOMMU cache coherent capable.
> 
> Without this print, we have no hint why the operation failed.
> 
> For example:
> 
> $ virsh start <domain>
> 	error: Failed to start domain <domain>
> 	error: Unable to open '/dev/vhost-vdpa-<idx>' for vdpa device:
> 	       Unknown error 524
> 
> Suggested-by: Eugenio Perez Martin <eperezma@redhat.com>
> Signed-off-by: Alvaro Karsz <alvaro.karsz@solid-run.com>

I'm not sure this is a good idea. Userspace is not supposed to be
able to trigger dev_err.

> ---
>  drivers/vhost/vdpa.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
> index 23db92388393..56287506aa0d 100644
> --- a/drivers/vhost/vdpa.c
> +++ b/drivers/vhost/vdpa.c
> @@ -1151,8 +1151,11 @@ static int vhost_vdpa_alloc_domain(struct vhost_vdpa *v)
>  	if (!bus)
>  		return -EFAULT;
>  
> -	if (!device_iommu_capable(dma_dev, IOMMU_CAP_CACHE_COHERENCY))
> +	if (!device_iommu_capable(dma_dev, IOMMU_CAP_CACHE_COHERENCY)) {
> +		dev_err(&v->dev,
> +			"Failed to allocate domain, device is not IOMMU cache coherent capable\n");
>  		return -ENOTSUPP;
> +	}
>  
>  	v->domain = iommu_domain_alloc(bus);
>  	if (!v->domain)
> -- 
> 2.34.1


  reply	other threads:[~2023-02-01 15:52 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-02-01 15:20 [PATCH] vhost-vdpa: print error when vhost_vdpa_alloc_domain fails Alvaro Karsz
2023-02-01 15:20 ` Alvaro Karsz
2023-02-01 15:52 ` Michael S. Tsirkin [this message]
2023-02-01 15:52   ` Michael S. Tsirkin
2023-02-01 15:54   ` Alvaro Karsz
2023-02-01 15:54     ` Alvaro Karsz
2023-02-01 16:03     ` Michael S. Tsirkin
2023-02-01 16:03       ` Michael S. Tsirkin
2023-02-01 16:51       ` Alvaro Karsz
2023-02-01 16:51         ` Alvaro Karsz
2023-02-02  8:42 ` [PATCH v2] vhost-vdpa: print warning " Alvaro Karsz
2023-02-02  8:42   ` Alvaro Karsz
2023-02-02 19:01   ` Eugenio Perez Martin

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