[PATCH 2/2] mm/hmm: Only set FAULT_FLAG_ALLOW_RETRY for non-blocking

[Alex Deucher]

On Tue, May 14, 2019 at 5:12 PM Kuehling, Felix <Felix.Kuehling at amd.com> wrote:
>
>
> On 2019-05-13 4:21 p.m., Deucher, Alexander wrote:
> > [CAUTION: External Email]
> > I reverted all the amdgpu HMM patches for 5.2 because they also
> > depended on this patch:
> > https://cgit.freedesktop.org/~agd5f/linux/commit/?h=drm-next-5.2-wip&id=ce05ef71564f7cbe270cd4337c36ee720ea534db
> > which did not have a clear line of sight for 5.2 either.
>
> When was that? I saw "Use HMM for userptr" in Dave's 5.2-rc1 pull
> request to Linus.

https://patchwork.kernel.org/patch/10875587/

Alex



>
>
> Regards,
>    Felix
>
>
> >
> > Alex
> > ------------------------------------------------------------------------
> > *From:* amd-gfx <amd-gfx-bounces at lists.freedesktop.org> on behalf of
> > Kuehling, Felix <Felix.Kuehling at amd.com>
> > *Sent:* Monday, May 13, 2019 3:36 PM
> > *To:* Jerome Glisse
> > *Cc:* linux-mm at kvack.org; airlied at gmail.com;
> > amd-gfx at lists.freedesktop.org; dri-devel at lists.freedesktop.org;
> > alex.deucher at amd.com
> > *Subject:* Re: [PATCH 2/2] mm/hmm: Only set FAULT_FLAG_ALLOW_RETRY for
> > non-blocking
> > [CAUTION: External Email]
> >
> > Hi Jerome,
> >
> > Do you want me to push the patches to your branch? Or are you going to
> > apply them yourself?
> >
> > Is your hmm-5.2-v3 branch going to make it into Linux 5.2? If so, do you
> > know when? I'd like to coordinate with Dave Airlie so that we can also
> > get that update into a drm-next branch soon.
> >
> > I see that Linus merged Dave's pull request for Linux 5.2, which
> > includes the first changes in amdgpu using HMM. They're currently broken
> > without these two patches.
> >
> > Thanks,
> >    Felix
> >
> > On 2019-05-10 4:14 p.m., Jerome Glisse wrote:
> > > [CAUTION: External Email]
> > >
> > > On Fri, May 10, 2019 at 07:53:24PM +0000, Kuehling, Felix wrote:
> > >> Don't set this flag by default in hmm_vma_do_fault. It is set
> > >> conditionally just a few lines below. Setting it unconditionally
> > >> can lead to handle_mm_fault doing a non-blocking fault, returning
> > >> -EBUSY and unlocking mmap_sem unexpectedly.
> > >>
> > >> Signed-off-by: Felix Kuehling <Felix.Kuehling at amd.com>
> > > Reviewed-by: Jérôme Glisse <jglisse at redhat.com>
> > >
> > >> ---
> > >>   mm/hmm.c | 2 +-
> > >>   1 file changed, 1 insertion(+), 1 deletion(-)
> > >>
> > >> diff --git a/mm/hmm.c b/mm/hmm.c
> > >> index b65c27d5c119..3c4f1d62202f 100644
> > >> --- a/mm/hmm.c
> > >> +++ b/mm/hmm.c
> > >> @@ -339,7 +339,7 @@ struct hmm_vma_walk {
> > >>   static int hmm_vma_do_fault(struct mm_walk *walk, unsigned long addr,
> > >>                            bool write_fault, uint64_t *pfn)
> > >>   {
> > >> -     unsigned int flags = FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_REMOTE;
> > >> +     unsigned int flags = FAULT_FLAG_REMOTE;
> > >>        struct hmm_vma_walk *hmm_vma_walk = walk->private;
> > >>        struct hmm_range *range = hmm_vma_walk->range;
> > >>        struct vm_area_struct *vma = walk->vma;
> > >> --
> > >> 2.17.1
> > >>
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