From mboxrd@z Thu Jan 1 00:00:00 1970 From: Robin Murphy Subject: Re: [PATCH] iommu/io-pgtable-arm: Fix iova_to_phys for block entries Date: Fri, 17 Jun 2016 15:07:36 +0100 Message-ID: <57640428.408@arm.com> References: <1466099078-3919-1-git-send-email-will.deacon@arm.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1466099078-3919-1-git-send-email-will.deacon-5wv7dgnIgG8@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: iommu-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: Will Deacon , linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org Cc: iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org List-Id: iommu@lists.linux-foundation.org On 16/06/16 18:44, Will Deacon wrote: > The implementation of iova_to_phys for the long-descriptor ARM > io-pgtable code always masks with the granule size when inserting the > low virtual address bits into the physical address determined from the > page tables. In cases where the leaf entry is found before the final > level of table (i.e. due to a block mapping), this results in rounding > down to the bottom page of the block mapping. Consequently, the physical > address range batching in the vfio_unmap_unpin is defeated and we end > up taking the long way home. > > This patch fixes the problem by masking the virtual address with the > appropriate mask for the level at which the leaf descriptor is located. > The short-descriptor code already gets this right, so no change is > needed there. With this, I now see VFIO unmapping at the same granularity as the initial mapping. To think of all the cumulative hours we've spent watching it split the blocks and go 4K at a time... *sigh* Tested-by: Robin Murphy > Reported-by: Robin Murphy > Signed-off-by: Will Deacon > --- > drivers/iommu/io-pgtable-arm.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/iommu/io-pgtable-arm.c b/drivers/iommu/io-pgtable-arm.c > index a1ed1b73fed4..f5c90e1366ce 100644 > --- a/drivers/iommu/io-pgtable-arm.c > +++ b/drivers/iommu/io-pgtable-arm.c > @@ -576,7 +576,7 @@ static phys_addr_t arm_lpae_iova_to_phys(struct io_pgtable_ops *ops, > return 0; > > found_translation: > - iova &= (ARM_LPAE_GRANULE(data) - 1); > + iova &= (ARM_LPAE_BLOCK_SIZE(lvl, data) - 1); > return ((phys_addr_t)iopte_to_pfn(pte,data) << data->pg_shift) | iova; > } > >