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

[Marc Zyngier <maz@kernel.org>]

On Tue, 29 Jun 2021 18:34:40 +0100,
Will Deacon <will@kernel.org> wrote:
> 
> On Fri, Jun 18, 2021 at 05:24:49PM +0100, Robin Murphy wrote:
> > 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>
> > ---
> >  drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 15 +++++++++++++++
> >  1 file changed, 15 insertions(+)
> 
> Any chance of getting the fastmodels updated instead? It feels like it
> has to happen *eventually*, and then there would be no need for this bodge.

That'd be ideal. What are the chances of that happening before the Sun
turns into a black hole?

> Will
> 
> > 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;
> > +}

Could this be expressed as a PCI quirk instead? It would at least keep
the ID matching out of the SMMU driver...

Thanks,

	M.

-- 
Without deviation from the norm, progress is not possible.
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