Commit 4644321f authored by Eric Auger's avatar Eric Auger Committed by Alex Williamson

vfio/type1: handle case where IOMMU does not support PAGE_SIZE size

Current vfio_pgsize_bitmap code hides the supported IOMMU page
sizes smaller than PAGE_SIZE. As a result, in case the IOMMU
does not support PAGE_SIZE page, the alignment check on map/unmap
is done with larger page sizes, if any. This can fail although
mapping could be done with pages smaller than PAGE_SIZE.

This patch modifies vfio_pgsize_bitmap implementation so that,
in case the IOMMU supports page sizes smaller than PAGE_SIZE
we pretend PAGE_SIZE is supported and hide sub-PAGE_SIZE sizes.
That way the user will be able to map/unmap buffers whose size/
start address is aligned with PAGE_SIZE. Pinning code uses that
granularity while iommu driver can use the sub-PAGE_SIZE size
to map the buffer.
Signed-off-by: default avatarEric Auger <eric.auger@linaro.org>
Acked-by: default avatarWill Deacon <will.deacon@arm.com>
Signed-off-by: default avatarAlex Williamson <alex.williamson@redhat.com>
parent 1276ece3
...@@ -403,13 +403,26 @@ static void vfio_remove_dma(struct vfio_iommu *iommu, struct vfio_dma *dma) ...@@ -403,13 +403,26 @@ static void vfio_remove_dma(struct vfio_iommu *iommu, struct vfio_dma *dma)
static unsigned long vfio_pgsize_bitmap(struct vfio_iommu *iommu) static unsigned long vfio_pgsize_bitmap(struct vfio_iommu *iommu)
{ {
struct vfio_domain *domain; struct vfio_domain *domain;
unsigned long bitmap = PAGE_MASK; unsigned long bitmap = ULONG_MAX;
mutex_lock(&iommu->lock); mutex_lock(&iommu->lock);
list_for_each_entry(domain, &iommu->domain_list, next) list_for_each_entry(domain, &iommu->domain_list, next)
bitmap &= domain->domain->ops->pgsize_bitmap; bitmap &= domain->domain->ops->pgsize_bitmap;
mutex_unlock(&iommu->lock); mutex_unlock(&iommu->lock);
/*
* In case the IOMMU supports page sizes smaller than PAGE_SIZE
* we pretend PAGE_SIZE is supported and hide sub-PAGE_SIZE sizes.
* That way the user will be able to map/unmap buffers whose size/
* start address is aligned with PAGE_SIZE. Pinning code uses that
* granularity while iommu driver can use the sub-PAGE_SIZE size
* to map the buffer.
*/
if (bitmap & ~PAGE_MASK) {
bitmap &= PAGE_MASK;
bitmap |= PAGE_SIZE;
}
return bitmap; return bitmap;
} }
......
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