Commit 4644321f authored Oct 29, 2015 by Eric Auger Committed by Alex Williamson Nov 03, 2015

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: Eric Auger <eric.auger@linaro.org>
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

parent 1276ece3

drivers/vfio/vfio_iommu_type1.c

+14 −1

Original line number	Diff line number	Diff line
		@@ -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;
		}