Re: 答复: [PATCH] drm/amdkfd: use vma_lookup() instead of find_vma()

[Felix Kuehling]

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@xxxxxxx>
> > time: 2022年10月18日 3:35
> > to: tomorrow Wang (王德明) <wangdeming@xxxxxxxxxx>;
> > airlied@xxxxxxxxx; daniel@xxxxxxxx; alexander.deucher@xxxxxxx;
> > christian.koenig@xxxxxxx; Xinhui.Pan@xxxxxxx
> > linux-kernel@xxxxxxxxxxxxxxx
> > 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@xxxxxxxxxx>
> > > ---
> > >    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;