Re: [PATCH] iommu/arm-smmu-v3: Add default domain quirk for Arm Fast Models

[Andre Przywara <andre.przywara@arm.com>]

On Fri, 18 Jun 2021 17:24:49 +0100
Robin Murphy <robin.murphy@arm.com> wrote:

Hi Robin,

> Arm Fast Models are still implementing legacy virtio-pci devices behind
> the SMMU, which continue to be problematic as "real hardware" devices
> (from the point of view of the simulated system) without the mitigating
> VIRTIO_F_ACCESS_PLATFORM feature.
> 
> Since we now have the ability to force passthrough on a device-specific
> basis, let's use it to work around this particular oddity so that people
> who just want to boot Linux on a model don't have to fiddle around with
> things to avoid the SMMU getting in the way by default (and I don't have
> to keep telling them which things...)
> 
> Signed-off-by: Robin Murphy <robin.murphy@arm.com>

So it looks somewhat quirky, but it indeed fixes the boot problems on
the RevC model for me.
And given that currently an out-of-the-box kernel build fails booting
(with the kernel DT), I'd like to see that merged.

Tested-by: Andre Przywara <andre.przywara@arm.com>

Thanks,
Andre

> ---
>  drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)
> 
> diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> index 54b2f27b81d4..13cf16e8f45b 100644
> --- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> +++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
> @@ -2649,6 +2649,20 @@ static int arm_smmu_dev_disable_feature(struct device *dev,
>  	}
>  }
>  
> +static int arm_smmu_def_domain_type(struct device *dev)
> +{
> +	if (dev_is_pci(dev)) {
> +		struct pci_dev *pdev = to_pci_dev(dev);
> +
> +		/* Legacy virtio-block devices on Arm Fast Models */
> +		if (pdev->vendor == 0x1af4 && pdev->device == 0x1001 &&
> +		    pdev->subsystem_vendor == 0x00ff && pdev->subsystem_device == 0x0002)
> +			return IOMMU_DOMAIN_IDENTITY;
> +	}
> +
> +	return 0;
> +}
> +
>  static struct iommu_ops arm_smmu_ops = {
>  	.capable		= arm_smmu_capable,
>  	.domain_alloc		= arm_smmu_domain_alloc,
> @@ -2673,6 +2687,7 @@ static struct iommu_ops arm_smmu_ops = {
>  	.sva_bind		= arm_smmu_sva_bind,
>  	.sva_unbind		= arm_smmu_sva_unbind,
>  	.sva_get_pasid		= arm_smmu_sva_get_pasid,
> +	.def_domain_type	= arm_smmu_def_domain_type,
>  	.pgsize_bitmap		= -1UL, /* Restricted during device attach */
>  	.owner			= THIS_MODULE,
>  };

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