Hi Alex,
While trying to get VFIO-PCI working on AArch64 (with 64k page size), I
stumbled over the following piece of code:
> static unsigned long vfio_pgsize_bitmap(struct vfio_iommu *iommu)
> {
> struct vfio_domain *domain;
> unsigned long bitmap = PAGE_MASK;
>
> mutex_lock(&iommu->lock);
> list_for_each_entry(domain, &iommu->domain_list, next)
> bitmap &= domain->domain->ops->pgsize_bitmap;
> mutex_unlock(&iommu->lock);
>
> return bitmap;
> }
The SMMU page mask is
[ 3.054302] arm-smmu e0a00000.smmu: Supported page sizes: 0x40201000
but after this function, we end up supporting one 2MB pages and above.
The reason for that is simple: You restrict the bitmap to PAGE_MASK and
above.
Now the big question is why you're doing that. I don't see why it would
be a problem if the IOMMU maps a page in smaller chunks.
So I tried to patch the code above with s/PAGE_MASK/1UL/ and everything
seems to run fine. But maybe we're not lacking some sanity checks?
Alex
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