From: Eric Auger Date: Thu, 29 Oct 2015 17:49:42 +0000 (+0000) Subject: vfio/type1: handle case where IOMMU does not support PAGE_SIZE size X-Git-Url: http://drtracing.org/?a=commitdiff_plain;h=4644321fd3c119a819ab24fd2bc2d1f9bca4a695;p=deliverable%2Flinux.git 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 Acked-by: Will Deacon Signed-off-by: Alex Williamson --- diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c index 57d8c37a002b..59d47cb638d5 100644 --- a/drivers/vfio/vfio_iommu_type1.c +++ b/drivers/vfio/vfio_iommu_type1.c @@ -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; }