On Wed, 2015-10-28 at 18:10 +0100, Eric Auger wrote: > Hi Alex, > On 10/28/2015 05:27 PM, Alex Williamson wrote: > > On Wed, 2015-10-28 at 13:12 +0000, Eric Auger wrote: > >> 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. > >> > >> vfio_pgsize_bitmap is modified to expose the IOMMU page sizes, > >> supported by all domains, even those smaller than PAGE_SIZE. The > >> alignment check on map is performed against PAGE_SIZE if the minimum > >> IOMMU size is less than PAGE_SIZE or against the min page size greater > >> than PAGE_SIZE. > >> > >> Signed-off-by: Eric Auger <eric.au...@linaro.org> > >> > >> --- > >> > >> This was tested on AMD Seattle with 64kB page host. ARM MMU 401 > >> currently expose 4kB, 2MB and 1GB page support. With a 64kB page host, > >> the map/unmap check is done against 2MB. Some alignment check fail > >> so VFIO_IOMMU_MAP_DMA fail while we could map using 4kB IOMMU page > >> size. > >> --- > >> drivers/vfio/vfio_iommu_type1.c | 25 +++++++++++-------------- > >> 1 file changed, 11 insertions(+), 14 deletions(-) > >> > >> diff --git a/drivers/vfio/vfio_iommu_type1.c > >> b/drivers/vfio/vfio_iommu_type1.c > >> index 57d8c37..13fb974 100644 > >> --- a/drivers/vfio/vfio_iommu_type1.c > >> +++ b/drivers/vfio/vfio_iommu_type1.c > >> @@ -403,7 +403,7 @@ 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; > > > > Isn't this and removing the WARN_ON()s the only real change in this > > patch? The rest looks like conversion to use IS_ALIGNED and the > > following test, that I don't really understand... > Yes basically you're right.
Ok, so with hopefully correcting my understand of what this does, isn't this effectively the same: diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c index 57d8c37..7db4f5a 100644 --- a/drivers/vfio/vfio_iommu_type1.c +++ b/drivers/vfio/vfio_iommu_type1.c @@ -403,13 +403,19 @@ static void vfio_remove_dma(struct vfio_iommu *iommu, stru 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); + /* Some comment about how the IOMMU API splits requests */ + if (bitmap & ~PAGE_MASK) { + bitmap &= PAGE_MASK; + bitmap |= PAGE_SIZE; + } + return bitmap; } This would also expose to the user that we're accepting PAGE_SIZE, which we weren't before, so it was not quite right to just let them do it anyway. I don't think we even need to get rid of the WARN_ONs, do we? Thanks, Alex > > > >> > >> mutex_lock(&iommu->lock); > >> list_for_each_entry(domain, &iommu->domain_list, next) > >> @@ -416,20 +416,18 @@ static unsigned long vfio_pgsize_bitmap(struct > >> vfio_iommu *iommu) > >> static int vfio_dma_do_unmap(struct vfio_iommu *iommu, > >> struct vfio_iommu_type1_dma_unmap *unmap) > >> { > >> - uint64_t mask; > >> struct vfio_dma *dma; > >> size_t unmapped = 0; > >> int ret = 0; > >> + unsigned int min_pagesz = __ffs(vfio_pgsize_bitmap(iommu)); > >> + unsigned int requested_alignment = (min_pagesz < PAGE_SIZE) ? > >> + PAGE_SIZE : min_pagesz; > > > > This one. If we're going to support sub-PAGE_SIZE mappings, why do we > > care to cap alignment at PAGE_SIZE? > My intent in this patch isn't to allow the user-space to map/unmap > sub-PAGE_SIZE buffers. The new test makes sure the mapped area is bigger > or equal than a host page whatever the supported page sizes. > > I noticed that chunk construction, pinning and other many things are > based on PAGE_SIZE and far be it from me to change that code! I want to > keep that minimal granularity for all those computation. > > However on iommu side, I would like to rely on the fact the iommu driver > is clever enough to choose the right page size and even to choose a size > that is smaller than PAGE_SIZE if this latter is not supported. > > > >> - mask = ((uint64_t)1 << __ffs(vfio_pgsize_bitmap(iommu))) - 1; > >> - > >> - if (unmap->iova & mask) > >> + if (!IS_ALIGNED(unmap->iova, requested_alignment)) > >> return -EINVAL; > >> - if (!unmap->size || unmap->size & mask) > >> + if (!unmap->size || !IS_ALIGNED(unmap->size, requested_alignment)) > >> return -EINVAL; > >> > >> - WARN_ON(mask & PAGE_MASK); > >> - > >> mutex_lock(&iommu->lock); > >> > >> /* > >> @@ -553,25 +551,24 @@ static int vfio_dma_do_map(struct vfio_iommu *iommu, > >> size_t size = map->size; > >> long npage; > >> int ret = 0, prot = 0; > >> - uint64_t mask; > >> struct vfio_dma *dma; > >> unsigned long pfn; > >> + unsigned int min_pagesz = __ffs(vfio_pgsize_bitmap(iommu)); > >> + unsigned int requested_alignment = (min_pagesz < PAGE_SIZE) ? > >> + PAGE_SIZE : min_pagesz; > >> > >> /* Verify that none of our __u64 fields overflow */ > >> if (map->size != size || map->vaddr != vaddr || map->iova != iova) > >> return -EINVAL; > >> > >> - mask = ((uint64_t)1 << __ffs(vfio_pgsize_bitmap(iommu))) - 1; > >> - > >> - WARN_ON(mask & PAGE_MASK); > >> - > >> /* READ/WRITE from device perspective */ > >> if (map->flags & VFIO_DMA_MAP_FLAG_WRITE) > >> prot |= IOMMU_WRITE; > >> if (map->flags & VFIO_DMA_MAP_FLAG_READ) > >> prot |= IOMMU_READ; > >> > >> - if (!prot || !size || (size | iova | vaddr) & mask) > >> + if (!prot || !size || > >> + !IS_ALIGNED(size | iova | vaddr, requested_alignment)) > >> return -EINVAL; > >> > >> /* Don't allow IOVA or virtual address wrap */ > > > > This is mostly ignoring the problems with sub-PAGE_SIZE mappings. For > > instance, we can only pin on PAGE_SIZE and therefore we only do > > accounting on PAGE_SIZE, so if the user does 4K mappings across your 64K > > page, that page gets pinned and accounted 16 times. Are we going to > > tell users that their locked memory limit needs to be 16x now? The rest > > of the code would need an audit as well to see what other sub-page bugs > > might be hiding. Thanks, > So if the user is not allowed to map sub-PAGE_SIZE buffers, accounting > still is based on PAGE_SIZE while iommu mapping can be based on > sub-PAGE_SIZE pages. I am misunderstanding something? > > Best Regards > > Eric > > > > Alex > > > > > > > -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html