From: Jason Gunthorpe <jgg@nvidia.com>
To: "Kasireddy, Vivek" <vivek.kasireddy@intel.com>
Cc: "dri-devel@lists.freedesktop.org"
<dri-devel@lists.freedesktop.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
David Hildenbrand <david@redhat.com>,
Mike Kravetz <mike.kravetz@oracle.com>,
Hugh Dickins <hughd@google.com>, Peter Xu <peterx@redhat.com>,
Gerd Hoffmann <kraxel@redhat.com>,
"Kim, Dongwon" <dongwon.kim@intel.com>,
"Chang, Junxiao" <junxiao.chang@intel.com>
Subject: Re: [RFC v1 1/3] mm/mmu_notifier: Add a new notifier for mapping updates (new pages)
Date: Tue, 18 Jul 2023 21:24:36 -0300 [thread overview]
Message-ID: <ZLctRBcOySnJh3rs@nvidia.com> (raw)
In-Reply-To: <IA0PR11MB71852354956EA85210AE5350F839A@IA0PR11MB7185.namprd11.prod.outlook.com>
On Wed, Jul 19, 2023 at 12:05:29AM +0000, 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 handle_pte_fault()
> after shmem_fault() gets called and for hugetlbfs, this seems to
> happen in hugetlb_fault().
That sounds about right
> Instead of introducing a new notifier, I did think about reusing
> (or overloading) .change_pte() but I did not fully understand the impact
> it would have on KVM, the only user of .change_pte().
Yes, change_pte will be called, I think, but under various locks. Why
would you need to change it?
What you are doing here doesn't make any sense within the design of
mmu_notifiers, eg:
> @ -2164,8 +2165,12 @@ static vm_fault_t shmem_fault(struct vm_fault *vmf)
> gfp, vma, vmf, &ret);
> if (err)
> return vmf_error(err);
> - if (folio)
> + if (folio) {
> vmf->page = folio_file_page(folio, vmf->pgoff);
> + if (ret == VM_FAULT_LOCKED)
> + mmu_notifier_update_mapping(vma->vm_mm, vmf->address,
> + page_to_pfn(vmf->page));
> + }
> return ret;
Hasn't even updated the PTEs yet, but it is invoking a callback??
Jason
next prev parent reply other threads:[~2023-07-19 0:24 UTC|newest]
Thread overview: 64+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-07-18 8:28 [RFC v1 0/3] udmabuf: Replace pages when there is FALLOC_FL_PUNCH_HOLE in memfd Vivek Kasireddy
2023-07-18 8:28 ` [RFC v1 1/3] mm/mmu_notifier: Add a new notifier for mapping updates (new pages) Vivek Kasireddy
2023-07-18 15:36 ` Jason Gunthorpe
2023-07-19 0:05 ` Kasireddy, Vivek
2023-07-19 0:24 ` Jason Gunthorpe [this message]
2023-07-19 6:19 ` Kasireddy, Vivek
2023-07-19 2:08 ` Alistair Popple
2023-07-20 7:43 ` Kasireddy, Vivek
2023-07-20 9:00 ` Alistair Popple
2023-07-24 7:54 ` Kasireddy, Vivek
2023-07-24 13:35 ` Jason Gunthorpe
2023-07-24 20:32 ` Kasireddy, Vivek
2023-07-25 4:30 ` Hugh Dickins
2023-07-25 22:24 ` Kasireddy, Vivek
2023-07-27 21:43 ` Peter Xu
2023-07-29 0:08 ` Kasireddy, Vivek
2023-07-31 17:05 ` Peter Xu
2023-08-01 7:11 ` Kasireddy, Vivek
2023-08-01 21:57 ` Peter Xu
2023-08-03 8:08 ` Kasireddy, Vivek
2023-08-03 13:02 ` Peter Xu
2023-07-25 12:36 ` Jason Gunthorpe
2023-07-25 22:44 ` Kasireddy, Vivek
2023-07-25 22:53 ` Jason Gunthorpe
2023-07-27 7:34 ` Kasireddy, Vivek
2023-07-27 11:58 ` Jason Gunthorpe
2023-07-29 0:46 ` Kasireddy, Vivek
2023-07-30 23:09 ` Jason Gunthorpe
2023-08-01 5:32 ` Kasireddy, Vivek
2023-08-01 12:19 ` Jason Gunthorpe
2023-08-01 12:22 ` David Hildenbrand
2023-08-01 12:23 ` Jason Gunthorpe
2023-08-01 12:26 ` David Hildenbrand
2023-08-01 12:26 ` Jason Gunthorpe
2023-08-01 12:28 ` David Hildenbrand
2023-08-01 17:53 ` Kasireddy, Vivek
2023-08-01 18:19 ` Jason Gunthorpe
2023-08-03 7:35 ` Kasireddy, Vivek
2023-08-03 12:14 ` Jason Gunthorpe
2023-08-03 12:32 ` David Hildenbrand
2023-08-04 0:14 ` Alistair Popple
2023-08-04 6:39 ` Kasireddy, Vivek
2023-08-04 7:23 ` David Hildenbrand
2023-08-04 21:53 ` Kasireddy, Vivek
2023-08-04 12:49 ` Jason Gunthorpe
2023-08-08 7:37 ` Kasireddy, Vivek
2023-08-08 12:42 ` Jason Gunthorpe
2023-08-16 6:43 ` Kasireddy, Vivek
2023-08-21 9:02 ` Alistair Popple
2023-08-22 6:14 ` Kasireddy, Vivek
2023-08-22 8:15 ` Alistair Popple
2023-08-24 6:48 ` Kasireddy, Vivek
2023-08-28 4:38 ` Kasireddy, Vivek
2023-08-30 16:02 ` Jason Gunthorpe
2023-07-25 3:38 ` Alistair Popple
2023-07-24 13:36 ` Alistair Popple
2023-07-24 13:37 ` Jason Gunthorpe
2023-07-24 20:42 ` Kasireddy, Vivek
2023-07-25 3:14 ` Alistair Popple
2023-07-18 8:28 ` [RFC v1 2/3] udmabuf: Replace pages when there is FALLOC_FL_PUNCH_HOLE in memfd Vivek Kasireddy
2023-08-02 12:40 ` Daniel Vetter
2023-08-03 8:24 ` Kasireddy, Vivek
2023-08-03 8:32 ` Daniel Vetter
2023-07-18 8:28 ` [RFC v1 3/3] selftests/dma-buf/udmabuf: Add tests for huge pages and FALLOC_FL_PUNCH_HOLE Vivek Kasireddy
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