Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751759AbdIAJnJ (ORCPT ); Fri, 1 Sep 2017 05:43:09 -0400 Received: from foss.arm.com ([217.140.101.70]:37276 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751558AbdIAJnI (ORCPT ); Fri, 1 Sep 2017 05:43:08 -0400 Subject: Re: [PATCH] iommu/dma: limit the IOVA allocated to dma-ranges region To: Joerg Roedel , Krishna Reddy Cc: iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org References: <1504217301-17216-1-git-send-email-vdumpa@nvidia.com> <20170901092609.GL19533@8bytes.org> From: Robin Murphy Message-ID: <3aeeb13e-045f-4cde-2cfb-62d4a879d207@arm.com> Date: Fri, 1 Sep 2017 10:43:05 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.1 MIME-Version: 1.0 In-Reply-To: <20170901092609.GL19533@8bytes.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2027 Lines: 52 On 01/09/17 10:26, Joerg Roedel wrote: > Adding Robin for review. > > On Thu, Aug 31, 2017 at 03:08:21PM -0700, Krishna Reddy wrote: >> Limit the IOVA allocated to dma-ranges specified for the device. >> This is necessary to ensure that IOVA allocated is addressable >> by device. Why? IOVA allocation is already constrained as much as it should be - if the device's DMA mask is wrong that's another problem, and this isn't the right place to fix it. dma_32bit_pfn means nothing more than an internal detail of IOVA allocator caching, which is subject to change[1]. As-is, on some platforms this patch will effectively force all allocations to fail already. Robin. [1]:https://www.mail-archive.com/iommu@lists.linux-foundation.org/msg19694.html >> Signed-off-by: Krishna Reddy >> --- >> drivers/iommu/dma-iommu.c | 5 +++++ >> 1 file changed, 5 insertions(+) >> >> diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c >> index 9d1cebe7f6cb..e8a8320b571b 100644 >> --- a/drivers/iommu/dma-iommu.c >> +++ b/drivers/iommu/dma-iommu.c >> @@ -364,6 +364,7 @@ static dma_addr_t iommu_dma_alloc_iova(struct iommu_domain *domain, >> struct iommu_dma_cookie *cookie = domain->iova_cookie; >> struct iova_domain *iovad = &cookie->iovad; >> unsigned long shift, iova_len, iova = 0; >> + dma_addr_t dma_end_addr; >> >> if (cookie->type == IOMMU_DMA_MSI_COOKIE) { >> cookie->msi_iova += size; >> @@ -381,6 +382,10 @@ static dma_addr_t iommu_dma_alloc_iova(struct iommu_domain *domain, >> if (iova_len < (1 << (IOVA_RANGE_CACHE_MAX_SIZE - 1))) >> iova_len = roundup_pow_of_two(iova_len); >> >> + /* Limit IOVA allocated to device addressable dma-ranges region. */ >> + dma_end_addr = (dma_addr_t)iovad->dma_32bit_pfn << shift; >> + dma_limit = dma_limit > dma_end_addr ? dma_end_addr : dma_limit; > > This looks like a good use-case for min(). > >> + >> if (domain->geometry.force_aperture) >> dma_limit = min(dma_limit, domain->geometry.aperture_end); >> >> -- >> 2.1.4