From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id ECF98ECE587 for ; Mon, 14 Oct 2019 15:46:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D1487217D9 for ; Mon, 14 Oct 2019 15:46:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387832AbfJNPqo (ORCPT ); Mon, 14 Oct 2019 11:46:44 -0400 Received: from foss.arm.com ([217.140.110.172]:47392 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2387802AbfJNPql (ORCPT ); Mon, 14 Oct 2019 11:46:41 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id CCF6C28; Mon, 14 Oct 2019 08:46:40 -0700 (PDT) Received: from [10.1.197.57] (e110467-lin.cambridge.arm.com [10.1.197.57]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id C04823F718; Mon, 14 Oct 2019 08:46:39 -0700 (PDT) Subject: Re: [PATCH] drm/panfrost: DMA map all pages shared with the GPU To: Steven Price , Daniel Vetter , David Airlie , Rob Herring , Tomeu Vizoso Cc: linux-kernel@vger.kernel.org, Alyssa Rosenzweig , dri-devel@lists.freedesktop.org References: <20191014151616.14099-1-steven.price@arm.com> From: Robin Murphy Message-ID: <99f279c5-e93d-ade6-cd97-56b3078da755@arm.com> Date: Mon, 14 Oct 2019 16:46:37 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <20191014151616.14099-1-steven.price@arm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-GB Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 14/10/2019 16:16, Steven Price wrote: > Pages shared with the GPU are (often) not cache coherent with the CPU so > cache maintenance is required to flush the CPU's caches. This was > already done when mapping pages on fault, but wasn't previously done > when mapping a freshly allocated page. > > Fix this by moving the call to dma_map_sg() into mmu_map_sg() ensuring > that it is always called when pages are mapped onto the GPU. Since > mmu_map_sg() can now fail the code also now has to handle an error > return. > > Not performing this cache maintenance can cause errors in the GPU output > (CPU caches are later flushed and overwrite the GPU output). In theory > it also allows the GPU (and by extension user space) to observe the > memory contents prior to sanitization. For the non-heap case, aren't the pages already supposed to be mapped by drm_gem_shmem_get_pages_sgt()? (Hmm, maybe I should try hooking up the GPU SMMU on my Juno to serve as a cheeky DMA-API-mishap detector...) Robin. > Fixes: f3ba91228e8e ("drm/panfrost: Add initial panfrost driver") > Signed-off-by: Steven Price > --- > drivers/gpu/drm/panfrost/panfrost_mmu.c | 20 ++++++++++++-------- > 1 file changed, 12 insertions(+), 8 deletions(-) > > diff --git a/drivers/gpu/drm/panfrost/panfrost_mmu.c b/drivers/gpu/drm/panfrost/panfrost_mmu.c > index bdd990568476..0495e48c238d 100644 > --- a/drivers/gpu/drm/panfrost/panfrost_mmu.c > +++ b/drivers/gpu/drm/panfrost/panfrost_mmu.c > @@ -248,6 +248,9 @@ static int mmu_map_sg(struct panfrost_device *pfdev, struct panfrost_mmu *mmu, > struct io_pgtable_ops *ops = mmu->pgtbl_ops; > u64 start_iova = iova; > > + if (!dma_map_sg(pfdev->dev, sgt->sgl, sgt->nents, DMA_BIDIRECTIONAL)) > + return -EINVAL; > + > for_each_sg(sgt->sgl, sgl, sgt->nents, count) { > unsigned long paddr = sg_dma_address(sgl); > size_t len = sg_dma_len(sgl); > @@ -275,6 +278,7 @@ int panfrost_mmu_map(struct panfrost_gem_object *bo) > struct panfrost_device *pfdev = to_panfrost_device(obj->dev); > struct sg_table *sgt; > int prot = IOMMU_READ | IOMMU_WRITE; > + int ret; > > if (WARN_ON(bo->is_mapped)) > return 0; > @@ -286,10 +290,12 @@ int panfrost_mmu_map(struct panfrost_gem_object *bo) > if (WARN_ON(IS_ERR(sgt))) > return PTR_ERR(sgt); > > - mmu_map_sg(pfdev, bo->mmu, bo->node.start << PAGE_SHIFT, prot, sgt); > - bo->is_mapped = true; > + ret = mmu_map_sg(pfdev, bo->mmu, bo->node.start << PAGE_SHIFT, > + prot, sgt); > + if (ret == 0) > + bo->is_mapped = true; > > - return 0; > + return ret; > } > > void panfrost_mmu_unmap(struct panfrost_gem_object *bo) > @@ -503,12 +509,10 @@ int panfrost_mmu_map_fault_addr(struct panfrost_device *pfdev, int as, u64 addr) > if (ret) > goto err_pages; > > - if (!dma_map_sg(pfdev->dev, sgt->sgl, sgt->nents, DMA_BIDIRECTIONAL)) { > - ret = -EINVAL; > + ret = mmu_map_sg(pfdev, bo->mmu, addr, > + IOMMU_WRITE | IOMMU_READ | IOMMU_NOEXEC, sgt); > + if (ret) > goto err_map; > - } > - > - mmu_map_sg(pfdev, bo->mmu, addr, IOMMU_WRITE | IOMMU_READ | IOMMU_NOEXEC, sgt); > > bo->is_mapped = true; > >