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([2a02:908:1252:fb60:8415:4d1c:ad0a:e8fd]) by smtp.gmail.com with ESMTPSA id u14sm8747191ejx.60.2021.03.29.12.36.47 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 29 Mar 2021 12:36:47 -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> <9a11c873-a362-b5d1-6d9c-e937034e267d@gmail.com> <84b3911173ad6beb246ba0a77f93d888ee6b393e.camel@mengyan1223.wang> <97c520ce107aa4d5fd96e2c380c8acdb63d45c37.camel@mengyan1223.wang> From: =?UTF-8?Q?Christian_K=c3=b6nig?= Message-ID: <7701fb71-9243-2d90-e1e1-d347a53b7d77@gmail.com> Date: Mon, 29 Mar 2021 21:36:46 +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: <97c520ce107aa4d5fd96e2c380c8acdb63d45c37.camel@mengyan1223.wang> 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 21:27 schrieb Xi Ruoyao: > Hi Christian, > > I don't think there is any constraint implemented to ensure `num_entries % > AMDGPU_GPU_PAGES_IN_CPU_PAGE == 0`. For example, in `amdgpu_vm_bo_map()`: > > /* validate the parameters */ > if (saddr & AMDGPU_GPU_PAGE_MASK || offset & AMDGPU_GPU_PAGE_MASK || > size == 0 || size & AMDGPU_GPU_PAGE_MASK) > return -EINVAL; > > /* snip */ > > saddr /= AMDGPU_GPU_PAGE_SIZE; > eaddr /= AMDGPU_GPU_PAGE_SIZE; > > /* snip */ > > mapping->start = saddr; > mapping->last = eaddr; > > > If we really want to ensure (mapping->last - mapping->start + 1) % > AMDGPU_GPU_PAGES_IN_CPU_PAGE == 0, then we should replace "AMDGPU_GPU_PAGE_MASK" > in "validate the parameters" with "PAGE_MASK". Yeah, good point. > I tried it and it broke userspace: Xorg startup fails with EINVAL with this > change. Well in theory it is possible that we always fill the GPUVM on a 4k basis while the native page size of the CPU is larger. Let me double check the code. BTW: What code base are you based on? The code your post here is quite outdated. Christian. > > On 2021-03-30 02:30 +0800, Xi Ruoyao wrote: >> On 2021-03-30 02:21 +0800, Xi Ruoyao wrote: >>> On 2021-03-29 20:10 +0200, Christian König wrote: >>>> 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. >>> I printk'ed the value of start & last, they are all a multiple of 4 >>> (AMDGPU_GPU_PAGES_IN_CPU_PAGE). >>> >>> However... `num_entries = last - start + 1` so it became some irrational >>> thing...  Either this line is wrong, or someone called >>> amdgpu_vm_bo_update_mapping with [start, last) instead of [start, last], which >>> is unexpected. >> I added BUG_ON(num_entries % AMDGPU_GPU_PAGES_IN_CPU_PAGE != 0), get: >> >>> Mar 30 02:28:27 xry111-A1901 kernel: [] >>> amdgpu_vm_bo_update_mapping.constprop.0+0x218/0xae8 >>> Mar 30 02:28:27 xry111-A1901 kernel: [] >>> amdgpu_vm_bo_update+0x270/0x4c0 >>> Mar 30 02:28:27 xry111-A1901 kernel: [] >>> amdgpu_gem_va_ioctl+0x40c/0x430 >>> Mar 30 02:28:27 xry111-A1901 kernel: [] >>> drm_ioctl_kernel+0xcc/0x120 >>> Mar 30 02:28:27 xry111-A1901 kernel: [] >>> drm_ioctl+0x220/0x408 >>> Mar 30 02:28:27 xry111-A1901 kernel: [] >>> amdgpu_drm_ioctl+0x58/0x98 >>> Mar 30 02:28:27 xry111-A1901 kernel: [] sys_ioctl+0xcc/0xe8 >>> Mar 30 02:28:27 xry111-A1901 kernel: [] >>> syscall_common+0x34/0x58 >>> >>>>>>> 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