linux-kernel - Re: 答复: [PATCH] drm/amdkfd: use vma_lookup() instead of find

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Date:   Wed, 19 Oct 2022 10:21:13 -0400
From:   Felix Kuehling <felix.kuehling@....com>
To:     tomorrow Wang (王德明) 
        <wangdeming@...pur.com>
Cc:     "airlied@...il.com" <airlied@...il.com>,
        "daniel@...ll.ch" <daniel@...ll.ch>,
        "alexander.deucher@....com" <alexander.deucher@....com>,
        "christian.koenig@....com" <christian.koenig@....com>,
        "Xinhui.Pan@....com" <Xinhui.Pan@....com>,
        "amd-gfx@...ts.freedesktop.org" <amd-gfx@...ts.freedesktop.org>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: 答复: [PATCH] drm/amdkfd: use vma_lookup() instead of find_vma()


Am 2022-10-17 um 20:47 schrieb tomorrow Wang (王德明):
> Hi,
> The function vma_lookup show below.  Vma valid check is included in it. Or, What other questions do you have?

My question is, why did you leave the find_vma call in 
svm_range_is_valid unchanged? I don't see a technical reason, but maybe 
I'm missing something. If there is a reason, please explain. If there is 
no reason, please fix that place as well for consistency.

Thanks,
   Felix


>
> static inline
> struct vm_area_struct *vma_lookup(struct mm_struct *mm, unsigned long addr)
>   {
>           struct vm_area_struct *vma = find_vma(mm, addr);
>
>           if (vma && addr < vma->vm_start)
>                   vma = NULL;
>
>           return vma;
>   }
>
>
>> from: Felix Kuehling <felix.kuehling@....com>
>> time: 2022年10月18日 3:35
>> to: tomorrow Wang (王德明) <wangdeming@...pur.com>;
>> airlied@...il.com; daniel@...ll.ch; alexander.deucher@....com;
>> christian.koenig@....com; Xinhui.Pan@....com
>> linux-kernel@...r.kernel.org
>> sub: Re: [PATCH] drm/amdkfd: use vma_lookup() instead of find_vma()
>>
>>
>> On 2022-10-06 22:48, Deming Wang wrote:
>>> Using vma_lookup() verifies the start address is contained in the
>>> found vma.  This results in easier to read the code.
>> Thank you for the patches. This and your other patch look good to me.
>> However, you missed one use of find_vma in svm_range_is_valid. Is that an
>> oversight or is there a reason why we need to use find_vma there?
>>
>> If you're going to respin it, you may also squash the two patches into one.
>>
>> Thanks,
>>     Felix
>>
>>
>>> Signed-off-by: Deming Wang <wangdeming@...pur.com>
>>> ---
>>>    drivers/gpu/drm/amd/amdkfd/kfd_svm.c | 12 ++++++------
>>>    1 file changed, 6 insertions(+), 6 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
>>> b/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
>>> index 64fdf63093a0..cabcc2ca3c23 100644
>>> --- a/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
>>> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_svm.c
>>> @@ -1586,8 +1586,8 @@ static int svm_range_validate_and_map(struct
>> mm_struct *mm,
>>>    		unsigned long npages;
>>>    		bool readonly;
>>>
>>> -		vma = find_vma(mm, addr);
>>> -		if (!vma || addr < vma->vm_start) {
>>> +		vma = vma_lookup(mm, addr);
>>> +		if (!vma) {
>>>    			r = -EFAULT;
>>>    			goto unreserve_out;
>>>    		}
>>> @@ -2542,8 +2542,8 @@ svm_range_get_range_boundaries(struct
>> kfd_process *p, int64_t addr,
>>>    	struct interval_tree_node *node;
>>>    	unsigned long start_limit, end_limit;
>>>
>>> -	vma = find_vma(p->mm, addr << PAGE_SHIFT);
>>> -	if (!vma || (addr << PAGE_SHIFT) < vma->vm_start) {
>>> +	vma = vma_lookup(p->mm, addr << PAGE_SHIFT);
>>> +	if (!vma) {
>>>    		pr_debug("VMA does not exist in address [0x%llx]\n", addr);
>>>    		return -EFAULT;
>>>    	}
>>> @@ -2871,8 +2871,8 @@ svm_range_restore_pages(struct amdgpu_device
>> *adev, unsigned int pasid,
>>>    	/* __do_munmap removed VMA, return success as we are handling stale
>>>    	 * retry fault.
>>>    	 */
>>> -	vma = find_vma(mm, addr << PAGE_SHIFT);
>>> -	if (!vma || (addr << PAGE_SHIFT) < vma->vm_start) {
>>> +	vma = vma_lookup(mm, addr << PAGE_SHIFT);
>>> +	if (!vma) {
>>>    		pr_debug("address 0x%llx VMA is removed\n", addr);
>>>    		r = 0;
>>>    		goto out_unlock_range;