On Wed, May 04, 2022 at 04:29:24PM +0100, Robin Murphy wrote:
> On 2022-05-04 15:54, Jason Gunthorpe wrote:
> > On Wed, May 04, 2022 at 03:42:09PM +0100, Robin Murphy wrote:
> >
> > > > This fixes an oops with VFIO and SMMUv3 because VFIO will call
> > > > iommu_detach_group() and then immediately iommu_domain_free(), but
> > > > SMMUv3 has no way to know that the domain it is holding a pointer to
> > > > has been freed. Now the iommu_detach_group() will assign the blocking
> > > > domain and SMMUv3 will no longer hold a stale domain reference.
> > >
> > > Thanks for taking this on! I do like the overall structure and naming much
> > > more than my initial sketch :)
> >
> > Thanks, no problem!
> > > > /*
> > > > - * If the group has been claimed already, do not re-attach the
> > > > default
> > > > - * domain.
> > > > + * A NULL domain means to call the detach_dev() op. New drivers
> > > > should
> > > > + * use a IOMMU_DOMAIN_IDENTITY domain instead of a NULL
> > > > default_domain
> > >
> > > Nit: IOMMU_DOMAIN_DMA is the baseline of default domain support,
> > > passthrough
> > > is more of an optional extra.
> >
> > Can you elaborate on this a bit more for the comment, I'm not sure I
> > understand all the historical stuff here.
>
> Well, the comment could effectively just be "New drivers should support
> default domains."
I made it this:
/*
* New drivers should support default domains and so the detach_dev() op
* will never be called. Otheriwse the NULL domain indicates the
* translation for the group should be set so it will work with the
* platform DMA ops.
*/
It also seems clear to me we should delete a bunch of detach_dev ops
from drivers?
I naively see that these drivers have the word IOMMU_DOMAIN_DMA in
them and also define detach_dev:
amd iommu
apple-dart
qcom_iommu
exynos-iommu
intel iommu
ipmmu-vmsa
mtk_iommu
rockchip-iommu
sprd-iommu
sun50i-iommu
These ones have IOMMU_DOMAIN_DMA but don't define detach_dev:
arm-smmuv3
arm-smmu
virtio-iommu
And I suppose these are the 'old' drivers:
fsl_pamu
omap-iommu
tegra-gart
tegra-smmu
I can get a patch for this as well, I think it will be clarifying to
remove this cruft.
Thanks
Jason
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