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

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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: Eric Auger <eric.auger@linaro.org>
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
This commit is contained in:
Eric Auger 2015-10-29 17:49:42 +00:00 committed by Alex Williamson
parent 1276ece32c
commit 4644321fd3
1 changed files with 14 additions and 1 deletions
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15
drivers/vfio/vfio_iommu_type1.c
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@ -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)
{
struct vfio_domain *domain;
unsigned long bitmap = PAGE_MASK;
unsigned long bitmap = ULONG_MAX;
mutex_lock(&iommu->lock);
list_for_each_entry(domain, &iommu->domain_list, next)
bitmap &= domain->domain->ops->pgsize_bitmap;
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;
}