From: "Christian König" <ckoenig.leichtzumerken@gmail.com>
To: "Xi Ruoyao" <xry111@mengyan1223.wang>,
"Alex Deucher" <alexander.deucher@amd.com>,
"Christian König" <christian.koenig@amd.com>
Cc: "David Airlie" <airlied@linux.ie>,
"Felix Kuehling" <Felix.Kuehling@amd.com>,
linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org,
"Dan Horák" <dan@danny.cz>,
amd-gfx@lists.freedesktop.org, "Daniel Vetter" <daniel@ffwll.ch>,
stable@vger.kernel.org
Subject: Re: [PATCH] drm/amdgpu: fix an underflow on non-4KB-page systems
Date: Mon, 29 Mar 2021 21:36:46 +0200 [thread overview]
Message-ID: <7701fb71-9243-2d90-e1e1-d347a53b7d77@gmail.com> (raw)
In-Reply-To: <97c520ce107aa4d5fd96e2c380c8acdb63d45c37.camel@mengyan1223.wang>
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outdated.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: [<ffffffff83c90750>]
>>> amdgpu_vm_bo_update_mapping.constprop.0+0x218/0xae8
>>> Mar 30 02:28:27 xry111-A1901 kernel: [<ffffffff83c922b8>]
>>> amdgpu_vm_bo_update+0x270/0x4c0
>>> Mar 30 02:28:27 xry111-A1901 kernel: [<ffffffff83c823ec>]
>>> amdgpu_gem_va_ioctl+0x40c/0x430
>>> Mar 30 02:28:27 xry111-A1901 kernel: [<ffffffff83c1cae4>]
>>> drm_ioctl_kernel+0xcc/0x120
>>> Mar 30 02:28:27 xry111-A1901 kernel: [<ffffffff83c1cfd8>]
>>> drm_ioctl+0x220/0x408
>>> Mar 30 02:28:27 xry111-A1901 kernel: [<ffffffff83c5ea48>]
>>> amdgpu_drm_ioctl+0x58/0x98
>>> Mar 30 02:28:27 xry111-A1901 kernel: [<ffffffff838feac4>] sys_ioctl+0xcc/0xe8
>>> Mar 30 02:28:27 xry111-A1901 kernel: [<ffffffff836e74f0>]
>>> 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 <xry111@mengyan1223.wang>
>>>>>>> Reported-by: Dan Horák <dan@danny.cz>
>>>>>>> Cc: stable@vger.kernel.org
>>>>>>> Signed-off-by: Xi Ruoyao <xry111@mengyan1223.wang>
>>>>>>> ---
>>>>>>> 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
next prev parent reply other threads:[~2021-03-29 19:37 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-29 17:53 [PATCH] drm/amdgpu: fix an underflow on non-4KB-page systems Xℹ Ruoyao
2021-03-29 18:04 ` Christian König
2021-03-29 18:08 ` Xi Ruoyao
2021-03-29 18:10 ` Christian König
2021-03-29 18:21 ` Xi Ruoyao
2021-03-29 18:30 ` Xi Ruoyao
2021-03-29 19:27 ` Xi Ruoyao
2021-03-29 19:36 ` Christian König [this message]
2021-03-29 19:40 ` Xi Ruoyao
2021-03-30 12:04 ` Xi Ruoyao
2021-03-30 12:55 ` Christian König
2021-03-30 13:00 ` Dan Horák
2021-03-30 13:02 ` Christian König
2021-03-30 13:02 ` Xi Ruoyao
2021-03-30 13:09 ` Xi Ruoyao
2021-03-30 13:23 ` Dan Horák
2021-03-30 13:24 ` Christian König
2021-03-30 15:46 ` Xi Ruoyao
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