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([2a02:908:1252:fb60:8415:4d1c:ad0a:e8fd]) by smtp.gmail.com with ESMTPSA id v8sm9586002edq.76.2021.03.29.11.10.45 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 29 Mar 2021 11:10:46 -0700 (PDT) Subject: Re: [PATCH] drm/amdgpu: fix an underflow on non-4KB-page systems To: Xi Ruoyao , Alex Deucher , =?UTF-8?Q?Christian_K=c3=b6nig?= Cc: David Airlie , Felix Kuehling , linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, =?UTF-8?Q?Dan_Hor=c3=a1k?= , amd-gfx@lists.freedesktop.org, Daniel Vetter , stable@vger.kernel.org References: <20210329175348.26859-1-xry111@mengyan1223.wang> From: =?UTF-8?Q?Christian_K=c3=b6nig?= Message-ID: <9a11c873-a362-b5d1-6d9c-e937034e267d@gmail.com> Date: Mon, 29 Mar 2021 20:10:45 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.7.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Am 29.03.21 um 20:08 schrieb Xi Ruoyao: > On 2021-03-29 20:04 +0200, Christian König wrote: >> Am 29.03.21 um 19:53 schrieb Xℹ Ruoyao: >>> If the initial value of `num_entires` (calculated at line 1654) is not >>> an integral multiple of `AMDGPU_GPU_PAGES_IN_CPU_PAGE`, in line 1681 a >>> value greater than the initial value will be assigned to it.  That causes >>> `start > last + 1` after line 1708.  Then in the next iteration an >>> underflow happens at line 1654.  It causes message >>> >>>      *ERROR* Couldn't update BO_VA (-12) >>> >>> printed in kernel log, and GPU hanging. >>> >>> Fortify the criteria of the loop to fix this issue. >> NAK the value of num_entries must always be a multiple of >> AMDGPU_GPU_PAGES_IN_CPU_PAGE or otherwise we corrupt the page tables. >> >> How do you trigger that? > Simply run "OpenGL area" from gtk3-demo (which just renders a triangle with GL) > under Xorg, on MIPS64. See the BugLink. You need to identify the root cause of this, most likely start or last are not a multiple of AMDGPU_GPU_PAGES_IN_CPU_PAGE. Christian. > >> Christian. >> >>> BugLink: https://gitlab.freedesktop.org/drm/amd/-/issues/1549 >>> Fixes: a39f2a8d7066 ("drm/amdgpu: nuke amdgpu_vm_bo_split_mapping v2") >>> Reported-by: Xi Ruoyao >>> Reported-by: Dan Horák >>> Cc: stable@vger.kernel.org >>> Signed-off-by: Xi Ruoyao >>> --- >>>   drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c | 2 +- >>>   1 file changed, 1 insertion(+), 1 deletion(-) >>> >>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c >>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c >>> index ad91c0c3c423..cee0cc9c8085 100644 >>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c >>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c >>> @@ -1707,7 +1707,7 @@ static int amdgpu_vm_bo_update_mapping(struct >>> amdgpu_device *adev, >>>                 } >>>                 start = tmp; >>> >>> -       } while (unlikely(start != last + 1)); >>> +       } while (unlikely(start < last + 1)); >>> >>>         r = vm->update_funcs->commit(¶ms, fence); >>> >>> >>> base-commit: a5e13c6df0e41702d2b2c77c8ad41677ebb065b3