From mboxrd@z Thu Jan 1 00:00:00 1970 From: Will Deacon Subject: Re: [RFC] vfio/type1: handle case where IOMMU does not support PAGE_SIZE size Date: Wed, 28 Oct 2015 15:37:51 +0000 Message-ID: <20151028153750.GH18966@arm.com> References: <1446037965-2341-1-git-send-email-eric.auger@linaro.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: eric.auger@st.com, kvm@vger.kernel.org, patches@linaro.org, linux-kernel@vger.kernel.org, alex.williamson@redhat.com, kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org To: Eric Auger Return-path: Content-Disposition: inline In-Reply-To: <1446037965-2341-1-git-send-email-eric.auger@linaro.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu List-Id: kvm.vger.kernel.org On Wed, Oct 28, 2015 at 01:12:45PM +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 > > --- > > 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; > > 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; max_t ? > > - 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; Same code here. Perhaps you need another function to get the alignment? Otherwise, this looks pretty straightforward to me; iommu_map will take care of splitting up the requests to the IOMMU driver so they are in the right chunks. Will