On Mon, Aug 28, 2023 at 04:38:01AM +, Kasireddy, Vivek wrote:
> Turns out, calling hmm_range_fault() from the invalidate callback was indeed
> a problem and the reason why new pages were not faulted-in. In other words,
> it looks like the invalidate callback is not the right place to invoke
Hi Alistair,
>
> > >
> > >> >> > > > No, adding HMM_PFN_REQ_WRITE still doesn't help in fixing the
> > >> issue.
> > >> >> > > > Although, I do not have THP enabled (or built-in), shmem does
> > not
> > >> evict
> > >> >> > > > the pages after hole punch as noted in the comment in
> > >> >>
Hi Alistair,
> >
> >> >> > > > No, adding HMM_PFN_REQ_WRITE still doesn't help in fixing the
> >> issue.
> >> >> > > > Although, I do not have THP enabled (or built-in), shmem does
> not
> >> evict
> >> >> > > > the pages after hole punch as noted in the comment in
> >> >> shmem_fallocate():
> >>
"Kasireddy, Vivek" writes:
> Hi Alistair,
>
>> >> > > > No, adding HMM_PFN_REQ_WRITE still doesn't help in fixing the
>> issue.
>> >> > > > Although, I do not have THP enabled (or built-in), shmem does not
>> evict
>> >> > > > the pages after hole punch as noted in the comment in
>> >>
Hi Alistair,
> >> > > > No, adding HMM_PFN_REQ_WRITE still doesn't help in fixing the
> issue.
> >> > > > Although, I do not have THP enabled (or built-in), shmem does not
> evict
> >> > > > the pages after hole punch as noted in the comment in
> >> shmem_fallocate():
> >> > >
> >> > > This is
"Kasireddy, Vivek" writes:
> Hi Jason,
>
>> > >
>> > > > No, adding HMM_PFN_REQ_WRITE still doesn't help in fixing the issue.
>> > > > Although, I do not have THP enabled (or built-in), shmem does not evict
>> > > > the pages after hole punch as noted in the comment in
>> shmem_fallocate():
>>
Hi Jason,
> > >
> > > > No, adding HMM_PFN_REQ_WRITE still doesn't help in fixing the issue.
> > > > Although, I do not have THP enabled (or built-in), shmem does not evict
> > > > the pages after hole punch as noted in the comment in
> shmem_fallocate():
> > >
> > > This is the source of all
On Tue, Aug 08, 2023 at 07:37:19AM +, Kasireddy, Vivek wrote:
> Hi Jason,
>
> >
> > > No, adding HMM_PFN_REQ_WRITE still doesn't help in fixing the issue.
> > > Although, I do not have THP enabled (or built-in), shmem does not evict
> > > the pages after hole punch as noted in the comment in
Hi Jason,
>
> > No, adding HMM_PFN_REQ_WRITE still doesn't help in fixing the issue.
> > Although, I do not have THP enabled (or built-in), shmem does not evict
> > the pages after hole punch as noted in the comment in shmem_fallocate():
>
> This is the source of all your problems.
>
> Things
Hi David,
> >
> Right, the "the zero pages are changed into writable pages" in your
> above comment just might not apply, because there won't be any
> >> page
> replacement (hopefully :) ).
> >>
> >>> If the page replacement does not happen when there are new
>
On Fri, Aug 04, 2023 at 06:39:22AM +, Kasireddy, Vivek wrote:
> No, adding HMM_PFN_REQ_WRITE still doesn't help in fixing the issue.
> Although, I do not have THP enabled (or built-in), shmem does not evict
> the pages after hole punch as noted in the comment in shmem_fallocate():
This is
On 04.08.23 08:39, Kasireddy, Vivek wrote:
Hi Alistair, David, Jason,
Right, the "the zero pages are changed into writable pages" in your
above comment just might not apply, because there won't be any
page
replacement (hopefully :) ).
If the page replacement does not happen when there are
Hi Alistair, David, Jason,
> >> Right, the "the zero pages are changed into writable pages" in your
> >> above comment just might not apply, because there won't be any
> page
> >> replacement (hopefully :) ).
>
> > If the page replacement does not happen when there are new
David Hildenbrand writes:
> On 03.08.23 14:14, Jason Gunthorpe wrote:
>> On Thu, Aug 03, 2023 at 07:35:51AM +, Kasireddy, Vivek wrote:
>>> Hi Jason,
>>>
>> Right, the "the zero pages are changed into writable pages" in your
>> above comment just might not apply, because there won't
Hi, Vivek,
On Thu, Aug 03, 2023 at 08:08:41AM +, Kasireddy, Vivek wrote:
> > Isn't it already too late though to wait that notification until page is
> > installed? Because here you pinned the page for DMA, I think it means
> > before a new page installed (but after the page is invalidated)
On 03.08.23 14:14, Jason Gunthorpe wrote:
On Thu, Aug 03, 2023 at 07:35:51AM +, Kasireddy, Vivek wrote:
Hi Jason,
Right, the "the zero pages are changed into writable pages" in your
above comment just might not apply, because there won't be any page
replacement (hopefully :) ).
If the
On Thu, Aug 03, 2023 at 07:35:51AM +, Kasireddy, Vivek wrote:
> Hi Jason,
>
> > > > Right, the "the zero pages are changed into writable pages" in your
> > > > above comment just might not apply, because there won't be any page
> > > > replacement (hopefully :) ).
> >
> > > If the page
Hi Peter,
> > Ok, I'll keep your use-case in mind but AFAICS, the process that creates
> > the udmabuf can be considered the owner. So, I think it makes sense that
> > the owner's VMA range can be registered (via mmu_notifiers) for updates.
>
> No need to have your special attention on this; my
Hi Jason,
> > > Right, the "the zero pages are changed into writable pages" in your
> > > above comment just might not apply, because there won't be any page
> > > replacement (hopefully :) ).
>
> > If the page replacement does not happen when there are new writes to the
> > area where the hole
On Tue, Aug 01, 2023 at 07:11:09AM +, Kasireddy, Vivek wrote:
> Ok, I'll keep your use-case in mind but AFAICS, the process that creates
> the udmabuf can be considered the owner. So, I think it makes sense that
> the owner's VMA range can be registered (via mmu_notifiers) for updates.
No
On Tue, Aug 01, 2023 at 05:53:32PM +, Kasireddy, Vivek wrote:
> > Right, the "the zero pages are changed into writable pages" in your
> > above comment just might not apply, because there won't be any page
> > replacement (hopefully :) ).
> If the page replacement does not happen when there
Hi David,
>
> On 01.08.23 14:26, Jason Gunthorpe wrote:
> > On Tue, Aug 01, 2023 at 02:26:03PM +0200, David Hildenbrand wrote:
> >> On 01.08.23 14:23, Jason Gunthorpe wrote:
> >>> On Tue, Aug 01, 2023 at 02:22:12PM +0200, David Hildenbrand wrote:
> On 01.08.23 14:19, Jason Gunthorpe wrote:
On 01.08.23 14:26, Jason Gunthorpe wrote:
On Tue, Aug 01, 2023 at 02:26:03PM +0200, David Hildenbrand wrote:
On 01.08.23 14:23, Jason Gunthorpe wrote:
On Tue, Aug 01, 2023 at 02:22:12PM +0200, David Hildenbrand wrote:
On 01.08.23 14:19, Jason Gunthorpe wrote:
On Tue, Aug 01, 2023 at
On Tue, Aug 01, 2023 at 02:26:03PM +0200, David Hildenbrand wrote:
> On 01.08.23 14:23, Jason Gunthorpe wrote:
> > On Tue, Aug 01, 2023 at 02:22:12PM +0200, David Hildenbrand wrote:
> > > On 01.08.23 14:19, Jason Gunthorpe wrote:
> > > > On Tue, Aug 01, 2023 at 05:32:38AM +, Kasireddy, Vivek
On 01.08.23 14:23, Jason Gunthorpe wrote:
On Tue, Aug 01, 2023 at 02:22:12PM +0200, David Hildenbrand wrote:
On 01.08.23 14:19, Jason Gunthorpe wrote:
On Tue, Aug 01, 2023 at 05:32:38AM +, Kasireddy, Vivek wrote:
You get another invalidate because the memfd removes the zero pages
that
On Tue, Aug 01, 2023 at 02:22:12PM +0200, David Hildenbrand wrote:
> On 01.08.23 14:19, Jason Gunthorpe wrote:
> > On Tue, Aug 01, 2023 at 05:32:38AM +, Kasireddy, Vivek wrote:
> >
> > > > You get another invalidate because the memfd removes the zero pages
> > > > that hmm_range_fault
On 01.08.23 14:19, Jason Gunthorpe wrote:
On Tue, Aug 01, 2023 at 05:32:38AM +, Kasireddy, Vivek wrote:
You get another invalidate because the memfd removes the zero pages
that hmm_range_fault installed in the PTEs before replacing them with
actual writable pages. Then you do the move, and
On Tue, Aug 01, 2023 at 05:32:38AM +, Kasireddy, Vivek wrote:
> > You get another invalidate because the memfd removes the zero pages
> > that hmm_range_fault installed in the PTEs before replacing them with
> > actual writable pages. Then you do the move, and another
> > hmm_range_fault, and
Hi Peter,
> >
> > > > > > > > > I'm not at all familiar with the udmabuf use case but that
> sounds
> > > > > > > > > brittle and effectively makes this notifier udmabuf specific
> right?
> > > > > > > > Oh, Qemu uses the udmabuf driver to provide Host Graphics
> > > > > components
> > > > > > >
Hi Jason,
>
> > > Later the importer decides it needs the memory again so it again asks
> > > for the dmabuf to be present, which does hmm_range_fault and gets
> > > whatever is appropriate at the time.
> > Unless I am missing something, I think just doing the above still won't
> > solve
> >
On Sat, Jul 29, 2023 at 12:08:25AM +, Kasireddy, Vivek wrote:
> Hi Peter,
>
> > > > > > > > I'm not at all familiar with the udmabuf use case but that
> > > > > > > > sounds
> > > > > > > > brittle and effectively makes this notifier udmabuf specific
> > > > > > > > right?
> > > > > > > Oh,
On Sat, Jul 29, 2023 at 12:46:59AM +, Kasireddy, Vivek wrote:
> > Later the importer decides it needs the memory again so it again asks
> > for the dmabuf to be present, which does hmm_range_fault and gets
> > whatever is appropriate at the time.
> Unless I am missing something, I think just
Hi Jason,
> > > > > If you still need the memory mapped then you re-call
> hmm_range_fault
> > > > > and re-obtain it. hmm_range_fault will resolve all the races and you
> > > > > get new pages.
> > >
> > > > IIUC, for my udmabuf use-case, it looks like calling hmm_range_fault
> > > > immediately
Hi Peter,
> > > > > > > I'm not at all familiar with the udmabuf use case but that sounds
> > > > > > > brittle and effectively makes this notifier udmabuf specific
> > > > > > > right?
> > > > > > Oh, Qemu uses the udmabuf driver to provide Host Graphics
> > > components
> > > > > > (such as
Hi, Vivek,
On Tue, Jul 25, 2023 at 10:24:21PM +, Kasireddy, Vivek wrote:
> Hi Hugh,
>
> >
> > On Mon, 24 Jul 2023, Kasireddy, Vivek wrote:
> > > Hi Jason,
> > > > On Mon, Jul 24, 2023 at 07:54:38AM +, Kasireddy, Vivek wrote:
> > > >
> > > > > > I'm not at all familiar with the udmabuf
On Thu, Jul 27, 2023 at 07:34:30AM +, Kasireddy, Vivek wrote:
> Hi Jason,
>
> >
> > On Tue, Jul 25, 2023 at 10:44:09PM +, Kasireddy, Vivek wrote:
> > > > If you still need the memory mapped then you re-call hmm_range_fault
> > > > and re-obtain it. hmm_range_fault will resolve all the
Hi Jason,
>
> On Tue, Jul 25, 2023 at 10:44:09PM +, Kasireddy, Vivek wrote:
> > > If you still need the memory mapped then you re-call hmm_range_fault
> > > and re-obtain it. hmm_range_fault will resolve all the races and you
> > > get new pages.
>
> > IIUC, for my udmabuf use-case, it
On Tue, Jul 25, 2023 at 10:44:09PM +, Kasireddy, Vivek wrote:
> > If you still need the memory mapped then you re-call hmm_range_fault
> > and re-obtain it. hmm_range_fault will resolve all the races and you
> > get new pages.
> IIUC, for my udmabuf use-case, it looks like calling
Hi Jason,
> > >
> > > > > I'm not at all familiar with the udmabuf use case but that sounds
> > > > > brittle and effectively makes this notifier udmabuf specific right?
> > > > Oh, Qemu uses the udmabuf driver to provide Host Graphics
> components
> > > > (such as Spice, Gstreamer, UI, etc)
Hi Hugh,
>
> On Mon, 24 Jul 2023, Kasireddy, Vivek wrote:
> > Hi Jason,
> > > On Mon, Jul 24, 2023 at 07:54:38AM +, Kasireddy, Vivek wrote:
> > >
> > > > > I'm not at all familiar with the udmabuf use case but that sounds
> > > > > brittle and effectively makes this notifier udmabuf specific
On Mon, Jul 24, 2023 at 08:32:45PM +, Kasireddy, Vivek wrote:
> Hi Jason,
>
> >
> > On Mon, Jul 24, 2023 at 07:54:38AM +, Kasireddy, Vivek wrote:
> >
> > > > I'm not at all familiar with the udmabuf use case but that sounds
> > > > brittle and effectively makes this notifier udmabuf
On Mon, 24 Jul 2023, Kasireddy, Vivek wrote:
> Hi Jason,
> > On Mon, Jul 24, 2023 at 07:54:38AM +, Kasireddy, Vivek wrote:
> >
> > > > I'm not at all familiar with the udmabuf use case but that sounds
> > > > brittle and effectively makes this notifier udmabuf specific right?
> > > Oh, Qemu
"Kasireddy, Vivek" writes:
> Hi Alistair,
Hi Vivek,
>> I wonder if we actually need the flag? IIUC it is already used for more
>> than just KSM. For example it can be called as part of fault handling by
>> set_pte_at_notify() in in wp_page_copy().
> Yes, I noticed that but what I really
Jason Gunthorpe writes:
> On Mon, Jul 24, 2023 at 07:54:38AM +, Kasireddy, Vivek wrote:
>> And replace mmu_notifier_update_mapping(vma->vm_mm, address, pte_pfn(*ptep))
>> in the current patch with
>> mmu_notifier_change_pte(vma->vm_mm, address, ptep, false));
>
> It isn't very useful
Hi Alistair,
> >>
> >> Yes, although obviously as I think you point out below you wouldn't be
> >> able to take any sleeping locks in mmu_notifier_update_mapping().
> > Yes, I understand that, but I am not sure how we can prevent any potential
> > notifier callback from taking sleeping locks
Hi Jason,
>
> On Mon, Jul 24, 2023 at 07:54:38AM +, Kasireddy, Vivek wrote:
>
> > > I'm not at all familiar with the udmabuf use case but that sounds
> > > brittle and effectively makes this notifier udmabuf specific right?
> > Oh, Qemu uses the udmabuf driver to provide Host Graphics
On Mon, Jul 24, 2023 at 11:36:47PM +1000, Alistair Popple wrote:
> My primary issue with this patch is the notifier is called without the
> PTL while providing a PTE value.
Right, this is no-go. The PTE value must be protected by the PTLs at
all times. We've made enough bugs already by being
On Mon, Jul 24, 2023 at 07:54:38AM +, Kasireddy, Vivek wrote:
> > I'm not at all familiar with the udmabuf use case but that sounds
> > brittle and effectively makes this notifier udmabuf specific right?
> Oh, Qemu uses the udmabuf driver to provide Host Graphics components
> (such as Spice,
"Kasireddy, Vivek" writes:
> Hi Alistair,
>
>>
>>
>> "Kasireddy, Vivek" writes:
>>
>> Yes, although obviously as I think you point out below you wouldn't be
>> able to take any sleeping locks in mmu_notifier_update_mapping().
> Yes, I understand that, but I am not sure how we can prevent
Hi Alistair,
>
>
> "Kasireddy, Vivek" writes:
>
> > Hi Alistair,
> >
> >>
> >> > diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> >> > index 64a3239b6407..1f2f0209101a 100644
> >> > --- a/mm/hugetlb.c
> >> > +++ b/mm/hugetlb.c
> >> > @@ -6096,8 +6096,12 @@ vm_fault_t hugetlb_fault(struct mm_struct
"Kasireddy, Vivek" writes:
> Hi Alistair,
>
>>
>> > diff --git a/mm/hugetlb.c b/mm/hugetlb.c
>> > index 64a3239b6407..1f2f0209101a 100644
>> > --- a/mm/hugetlb.c
>> > +++ b/mm/hugetlb.c
>> > @@ -6096,8 +6096,12 @@ vm_fault_t hugetlb_fault(struct mm_struct
>> *mm, struct vm_area_struct *vma,
Hi Alistair,
>
> > diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> > index 64a3239b6407..1f2f0209101a 100644
> > --- a/mm/hugetlb.c
> > +++ b/mm/hugetlb.c
> > @@ -6096,8 +6096,12 @@ vm_fault_t hugetlb_fault(struct mm_struct
> *mm, struct vm_area_struct *vma,
> > * hugetlb_no_page will
Hi Jason,
>
> On Wed, Jul 19, 2023 at 12:05:29AM +, Kasireddy, Vivek wrote:
>
> > > If there is no change to the PTEs then it is hard to see why this
> > > would be part of a mmu_notifier.
> > IIUC, the PTEs do get changed but only when a new page is faulted in.
> > For shmem, it looks like
Vivek Kasireddy writes:
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 64a3239b6407..1f2f0209101a 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -6096,8 +6096,12 @@ vm_fault_t hugetlb_fault(struct mm_struct *mm, struct
> vm_area_struct *vma,
>* hugetlb_no_page will
On Wed, Jul 19, 2023 at 12:05:29AM +, Kasireddy, Vivek wrote:
> > If there is no change to the PTEs then it is hard to see why this
> > would be part of a mmu_notifier.
> IIUC, the PTEs do get changed but only when a new page is faulted in.
> For shmem, it looks like the PTEs are updated in
Hi Jason,
>
> On Tue, Jul 18, 2023 at 01:28:56AM -0700, Vivek Kasireddy wrote:
> > Currently, there does not appear to be any mechanism for letting
> > drivers or other kernel entities know about updates made in a
> > mapping particularly when a new page is faulted in. Providing
> >
On Tue, Jul 18, 2023 at 01:28:56AM -0700, Vivek Kasireddy wrote:
> Currently, there does not appear to be any mechanism for letting
> drivers or other kernel entities know about updates made in a
> mapping particularly when a new page is faulted in. Providing
> notifications for such situations is
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