Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752385AbcLFEE1 (ORCPT ); Mon, 5 Dec 2016 23:04:27 -0500 Received: from hqemgate15.nvidia.com ([216.228.121.64]:15676 "EHLO hqemgate15.nvidia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751567AbcLFEEX (ORCPT ); Mon, 5 Dec 2016 23:04:23 -0500 X-PGP-Universal: processed; by hqnvupgp07.nvidia.com on Mon, 05 Dec 2016 08:02:17 -0800 Subject: Re: [PATCH 1/1] vfio iommu type1: set size to PAGE_SIZE while looking for iova in dma list To: Alex Williamson References: <1480972081-773-1-git-send-email-kwankhede@nvidia.com> <20161205155421.075bbec5@t450s.home> CC: , , , , , X-Nvconfidentiality: public From: Kirti Wankhede Message-ID: <130cf141-d9a0-4730-2a99-46eeb5dae664@nvidia.com> Date: Tue, 6 Dec 2016 09:26:36 +0530 MIME-Version: 1.0 In-Reply-To: <20161205155421.075bbec5@t450s.home> X-Originating-IP: [10.24.71.15] X-ClientProxiedBy: DRUKMAIL102.nvidia.com (10.25.59.20) To bgmail102.nvidia.com (10.25.59.11) Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3535 Lines: 93 On 12/6/2016 4:24 AM, Alex Williamson wrote: > On Tue, 6 Dec 2016 02:38:01 +0530 > Kirti Wankhede wrote: > >> In the functions of pin_pages/unpin_pages from mdev vendor driver, >> vfio_find_dma() should be called with size as PAGE_SIZE instead of 0. >> vfio_find_dma() searches for the range in dma_list. >> >> In vfio_dma_do_unmap(), vfio_find_dma() when used to look for start >> address of unmap->iova, size should be 1, not 0. Otherwise vfio_find_dma() >> returns NULL. > > Hi Kirti, > > I'd prefer to fix the preexisting case of this issue as a separate > patch, we might want to backport it for stable trees separately from the > new cases introduced with mdev. It would also be great if we could go > into some detail about why size=0 doesn't work in these cases, ie. > vfio_find_dma() accounting for the end address of the range makes it > fall through at the wrong branch point. For the case of the > preexisting issue, it would also be useful to mention that the other > case of passing size=0 works correctly due to the -1 in the start > address calculation. Finally, I think I agree with your choice to use > PAGE_SIZE in one case and 1 in the preexisting case, but perhaps we > could spell that out as one is related to a page size interface and the > other is trying to test boundary conditions. Thanks, > Thanks Alex, Actual problem here is: vfio_dma keeps track of address range from (dma->iova + 0) to (dma->iova + dma->size - 1), while vfio_find_dma() search logic looks for range from (dma->iova + 1) to (dma->iova + dma->size). So either we have to fix the size argument send to vfio_find_dma() or we have to fix rb-tree creation and search logic. I took the former path here. I'll add this detail in commit description and split it as you mentioned above. Thanks, Kirti > Alex > >> Signed-off-by: Kirti Wankhede >> Signed-off-by: Neo Jia >> Change-Id: Iee6fd45441c342b5e8626087046b2e0075d19a08 >> --- >> drivers/vfio/vfio_iommu_type1.c | 8 ++++---- >> 1 file changed, 4 insertions(+), 4 deletions(-) >> >> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c >> index a28fbddb505c..023fba7b8d5a 100644 >> --- a/drivers/vfio/vfio_iommu_type1.c >> +++ b/drivers/vfio/vfio_iommu_type1.c >> @@ -581,7 +581,7 @@ static int vfio_iommu_type1_pin_pages(void *iommu_data, >> struct vfio_pfn *vpfn; >> >> iova = user_pfn[i] << PAGE_SHIFT; >> - dma = vfio_find_dma(iommu, iova, 0); >> + dma = vfio_find_dma(iommu, iova, PAGE_SIZE); >> if (!dma) { >> ret = -EINVAL; >> goto pin_unwind; >> @@ -622,7 +622,7 @@ pin_unwind: >> dma_addr_t iova; >> >> iova = user_pfn[j] << PAGE_SHIFT; >> - dma = vfio_find_dma(iommu, iova, 0); >> + dma = vfio_find_dma(iommu, iova, PAGE_SIZE); >> vfio_unpin_page_external(dma, iova, do_accounting); >> phys_pfn[j] = 0; >> } >> @@ -659,7 +659,7 @@ static int vfio_iommu_type1_unpin_pages(void *iommu_data, >> dma_addr_t iova; >> >> iova = user_pfn[i] << PAGE_SHIFT; >> - dma = vfio_find_dma(iommu, iova, 0); >> + dma = vfio_find_dma(iommu, iova, PAGE_SIZE); >> if (!dma) >> goto unpin_exit; >> vfio_unpin_page_external(dma, iova, do_accounting); >> @@ -826,7 +826,7 @@ again: >> * mappings within the range. >> */ >> if (iommu->v2) { >> - dma = vfio_find_dma(iommu, unmap->iova, 0); >> + dma = vfio_find_dma(iommu, unmap->iova, 1); >> if (dma && dma->iova != unmap->iova) { >> ret = -EINVAL; >> goto unlock; >