Re: [PATCH] iommu/intel-iommu: set as DUMMY_DEVICE_DOMAIN_INFO if no IOMMU

[Lu Baolu]

Hi,

On 2020/2/3 17:10, Jian-Hong Pan wrote:
> If the device has no IOMMU, it still invokes iommu_need_mapping during
> intel_alloc_coherent. However, iommu_need_mapping can only check the
> device is DUMMY_DEVICE_DOMAIN_INFO or not. This patch marks the device
> is a DUMMY_DEVICE_DOMAIN_INFO if the device has no IOMMU.
>
> Signed-off-by: Jian-Hong Pan <jian-hong@xxxxxxxxxxxx>
> ---
>   drivers/iommu/intel-iommu.c | 4 +++-
>   1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
> index 35a4a3abedc6..878bc986a015 100644
> --- a/drivers/iommu/intel-iommu.c
> +++ b/drivers/iommu/intel-iommu.c
> @@ -5612,8 +5612,10 @@ static int intel_iommu_add_device(struct device *dev)
>   	int ret;
>   
>   	iommu = device_to_iommu(dev, &bus, &devfn);
> -	if (!iommu)
> +	if (!iommu) {
> +		dev->archdata.iommu = DUMMY_DEVICE_DOMAIN_INFO;

Is this a DMA capable device? I am afraid some real bugs might be
covered up if we marking the device as IOMMU dummy here.

Best regards,
baolu

>   		return -ENODEV;
> +	}
>   
>   	iommu_device_link(&iommu->iommu, dev);
>