From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1) server-digest SHA256) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1D53B606A31A for ; Sun, 1 Nov 2026 01:42:52 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key, unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=CY7CxXIM Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 374EF10E025; Sun, 1 Nov 2026 01:42:46 +0000 (UTC) Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by gabe.freedesktop.org (Postfix) with ESMTPS id E230310E025 for ; Sun, 1 Nov 2026 01:42:39 +0000 (UTC) Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id 29933400D8; Sun, 1 Nov 2026 01:42:39 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id C4DFB1F000C1; Sun, 1 Nov 2026 01:42:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1793497359; bh=Y3wAkSULnghY3p9q0qChnuIgIwOMmMN+2gBezIZ1ISI=; h=From:Subject:Reply-To:To:Cc:In-Reply-To:References:Date; b=CY7CxXIM+MUu+50YgLU4vggsjWxa1X5RUs+nWLUvmAO8/23hpJF2PwkFozcdxLbfX ha5ZCsZ7BLM/VgNfbxHZuhP4rHbe8q/SndRijSWlQZ91KLNhsQEE8TOxjmXJHd+J/h o7d3dvDwtrG0xfi1y8mdQi+ltbZs7vD0x249tdEas+eiNRwdg0Lr+4mRMvoU1JIvT2 zpNjPw65JV/sj+18zrHr9Om/UrHpTDlmKpzkb+tihAEz9cSzqPpCJx1Gu4k4Amkug7 4zDrk2WWFpewKWJo8MSfufc4sotEf/+Y5lkIDux69Ms8cYbh6R1Qya1FoOIh/cROXP lYIUamc3mwHIw== Message-ID: From: sashiko-bot@kernel.org Subject: Re: [PATCH] drm/amdkfd: Only take the VRAM path for KFD device pages in svm_range_dma_map_dev To: "Matthew Krebs" Cc: dri-devel@lists.freedesktop.org In-Reply-To: <20261101012500.7048-1-matthewkrebs8@gmail.com> References: <20261101012500.7048-1-matthewkrebs8@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Date: Sun, 01 Nov 2026 01:42:38 +0000 X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: sashiko-reviews@lists.linux.dev Sender: "dri-devel" X-Spam-Status: No, score=-10.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=4.0.1 X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 X-Archived-By: Thank you for your contribution! Sashiko AI review found 1 potential issue(= s) to consider: - [Medium] drm/amdkfd: dma_map_page() fails on DAX ZONE_DEVICE pages with D= MA_API_DEBUG -- commit 0eacef2f328edc8a87aa6b82601cf66a9676e3be Author: Matthew Krebs drm/amdkfd: Only take the VRAM path for KFD device pages in svm_range_dma_m= ap_dev This commit restricts the VRAM mapping branch in svm_range_dma_map_dev() to device-private and device-coherent pages so that other ZONE_DEVICE pages, s= uch as fsdax and device-dax mappings, are DMA mapped instead of dereferencing a potentially NULL prange->svm_bo. > diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_svm.c b/drivers/gpu/drm/amd/a= mdkfd/kfd_svm.c > index ed5e3318877be..354184829e1d6 100644 > --- a/drivers/gpu/drm/amd/amdkfd/kfd_svm.c > +++ b/drivers/gpu/drm/amd/amdkfd/kfd_svm.c > @@ -180,7 +180,12 @@ svm_range_dma_map_dev(struct amdgpu_device *adev, st= ruct svm_range *prange, > dma_unmap_page(dev, addr[i], PAGE_SIZE, dir); > =20 > page =3D hmm_pfn_to_page(hmm_pfns[i]); > - if (is_zone_device_page(page)) { > + /* > + * Only KFD's own VRAM pages (device private or device coherent) > + * take the VRAM path. Other ZONE_DEVICE pages, such as fsdax or > + * device-dax memory, are system memory and are DMA mapped below. > + */ > + if (is_device_private_page(page) || is_device_coherent_page(page)) { [Severity: Medium] When fsdax (MEMORY_DEVICE_FS_DAX) or device-dax (MEMORY_DEVICE_GENERIC) pag= es skip this branch in drivers/gpu/drm/amd/amdkfd/kfd_svm.c:svm_range_dma_map_dev()= , they fall through to dma_map_page(): drivers/gpu/drm/amd/amdkfd/kfd_svm.c:svm_range_dma_map_dev() { ... if (is_device_private_page(page) || is_device_coherent_page(page)) { ... continue; } addr[i] =3D dma_map_page(dev, page, 0, PAGE_SIZE, dir); ... } In kernel/dma/mapping.c:dma_map_page_attrs(), all ZONE_DEVICE pages are rej= ected when CONFIG_DMA_API_DEBUG is enabled: kernel/dma/mapping.c:dma_map_page_attrs() { ... if (IS_ENABLED(CONFIG_DMA_API_DEBUG) && WARN_ON_ONCE(is_zone_device_page(page))) return DMA_MAPPING_ERROR; ... } Won't mapping a fsdax or device-dax range through the KFD SVM ioctl (kfd_ioctl_svm() -> svm_ioctl() -> svm_range_set_attr() -> svm_range_validate_and_map() -> svm_range_dma_map() -> svm_range_dma_map_de= v()) trigger this WARN_ON_ONCE() and fail with -ENOMEM when CONFIG_DMA_API_DEBUG= is enabled? Should svm_range_dma_map_dev() and its unmap path use dma_map_phys() and dma_unmap_phys() (similar to hmm_dma_map_pfn() in mm/hmm.c) instead of dma_map_page() and dma_unmap_page() when mapping non-VRAM ZONE_DEVICE pages? --=20 Sashiko AI review =C2=B7 https://sashiko.dev/#/patchset/20261101012500.7048= -1-matthewkrebs8@gmail.com?part=3D1