From: Jason Gunthorpe <jgg@ziepe.ca>
To: Peter Xu <peterx@redhat.com>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
Mike Rapoport <rppt@linux.vnet.ibm.com>,
Mike Kravetz <mike.kravetz@oracle.com>,
Jerome Glisse <jglisse@redhat.com>,
"Kirill A . Shutemov" <kirill@shutemov.name>,
Hugh Dickins <hughd@google.com>,
Axel Rasmussen <axelrasmussen@google.com>,
Matthew Wilcox <willy@infradead.org>,
Andrew Morton <akpm@linux-foundation.org>,
Andrea Arcangeli <aarcange@redhat.com>,
Nadav Amit <nadav.amit@gmail.com>
Subject: Re: [PATCH RFC 07/30] mm/swap: Introduce the idea of special swap ptes
Date: Mon, 18 Jan 2021 15:40:13 -0400 [thread overview]
Message-ID: <20210118194013.GM4605@ziepe.ca> (raw)
In-Reply-To: <20210115170907.24498-8-peterx@redhat.com>
On Fri, Jan 15, 2021 at 12:08:44PM -0500, Peter Xu wrote:
> We used to have special swap entries, like migration entries, hw-poison
> entries, device private entries, etc.
>
> Those "special swap entries" reside in the range that they need to be at least
> swap entries first, and their types are decided by swp_type(entry).
>
> This patch introduces another idea called "special swap ptes".
>
> It's very easy to get confused against "special swap entries", but a speical
> swap pte should never contain a swap entry at all. It means, it's illegal to
> call pte_to_swp_entry() upon a special swap pte.
>
> Make the uffd-wp special pte to be the first special swap pte.
>
> Before this patch, is_swap_pte()==true means one of the below:
>
> (a.1) The pte has a normal swap entry (non_swap_entry()==false). For
> example, when an anonymous page got swapped out.
>
> (a.2) The pte has a special swap entry (non_swap_entry()==true). For
> example, a migration entry, a hw-poison entry, etc.
>
> After this patch, is_swap_pte()==true means one of the below, where case (b) is
> added:
>
> (a) The pte contains a swap entry.
>
> (a.1) The pte has a normal swap entry (non_swap_entry()==false). For
> example, when an anonymous page got swapped out.
>
> (a.2) The pte has a special swap entry (non_swap_entry()==true). For
> example, a migration entry, a hw-poison entry, etc.
>
> (b) The pte does not contain a swap entry at all (so it cannot be passed
> into pte_to_swp_entry()). For example, uffd-wp special swap pte.
Does the stuff in hmm.c need updating too?
if (!pte_present(pte)) {
swp_entry_t entry = pte_to_swp_entry(pte);
Jason
next prev parent reply other threads:[~2021-01-18 19:40 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-15 17:08 [PATCH RFC 00/30] userfaultfd-wp: Support shmem and hugetlbfs Peter Xu
2021-01-15 17:08 ` [PATCH RFC 01/30] mm/thp: Simplify copying of huge zero page pmd when fork Peter Xu
2021-01-15 17:08 ` [PATCH RFC 02/30] mm/userfaultfd: Fix uffd-wp special cases for fork() Peter Xu
2021-01-15 17:08 ` [PATCH RFC 03/30] mm/userfaultfd: Fix a few thp pmd missing uffd-wp bit Peter Xu
2021-01-15 17:08 ` [PATCH RFC 04/30] shmem/userfaultfd: Take care of UFFDIO_COPY_MODE_WP Peter Xu
2021-01-15 17:08 ` [PATCH RFC 05/30] mm: Clear vmf->pte after pte_unmap_same() returns Peter Xu
2021-01-15 17:08 ` [PATCH RFC 06/30] mm/userfaultfd: Introduce special pte for unmapped file-backed mem Peter Xu
2021-01-15 17:08 ` [PATCH RFC 07/30] mm/swap: Introduce the idea of special swap ptes Peter Xu
2021-01-18 19:40 ` Jason Gunthorpe [this message]
2021-01-19 14:24 ` Peter Xu
2021-01-15 17:08 ` [PATCH RFC 08/30] shmem/userfaultfd: Handle uffd-wp special pte in page fault handler Peter Xu
2021-01-15 17:08 ` [PATCH RFC 09/30] mm: Drop first_index/last_index in zap_details Peter Xu
2021-01-15 17:08 ` [PATCH RFC 10/30] mm: Introduce zap_details.zap_flags Peter Xu
2021-01-15 17:08 ` [PATCH RFC 11/30] mm: Introduce ZAP_FLAG_SKIP_SWAP Peter Xu
2021-01-15 17:08 ` [PATCH RFC 12/30] mm: Pass zap_flags into unmap_mapping_pages() Peter Xu
2021-01-15 17:08 ` [PATCH RFC 13/30] shmem/userfaultfd: Persist uffd-wp bit across zapping for file-backed Peter Xu
2021-01-15 17:08 ` [PATCH RFC 14/30] shmem/userfaultfd: Allow wr-protect none pte for file-backed mem Peter Xu
2021-01-15 17:08 ` [PATCH RFC 15/30] shmem/userfaultfd: Allows file-back mem to be uffd wr-protected on thps Peter Xu
2021-01-15 17:08 ` [PATCH RFC 16/30] shmem/userfaultfd: Handle the left-overed special swap ptes Peter Xu
2021-01-15 17:08 ` [PATCH RFC 17/30] shmem/userfaultfd: Pass over uffd-wp special swap pte when fork() Peter Xu
2021-01-15 17:08 ` [PATCH RFC 18/30] hugetlb/userfaultfd: Hook page faults for uffd write protection Peter Xu
2021-01-15 17:08 ` [PATCH RFC 19/30] hugetlb/userfaultfd: Take care of UFFDIO_COPY_MODE_WP Peter Xu
2021-01-15 17:08 ` [PATCH RFC 20/30] hugetlb/userfaultfd: Handle UFFDIO_WRITEPROTECT Peter Xu
2021-01-15 17:08 ` [PATCH RFC 21/30] hugetlb: Pass vma into huge_pte_alloc() Peter Xu
2021-01-28 22:59 ` Axel Rasmussen
2021-01-29 22:31 ` Peter Xu
2021-01-30 8:08 ` Axel Rasmussen
2021-01-15 17:08 ` [PATCH RFC 22/30] hugetlb/userfaultfd: Forbid huge pmd sharing when uffd enabled Peter Xu
2021-01-15 17:09 ` [PATCH RFC 23/30] mm/hugetlb: Introduce huge version of special swap pte helpers Peter Xu
2021-01-15 17:09 ` [PATCH RFC 24/30] mm/hugetlb: Move flush_hugetlb_tlb_range() into hugetlb.h Peter Xu
2021-01-15 17:09 ` [PATCH RFC 25/30] hugetlb/userfaultfd: Unshare all pmds for hugetlbfs when register wp Peter Xu
2021-01-15 17:09 ` [PATCH RFC 26/30] hugetlb/userfaultfd: Handle uffd-wp special pte in hugetlb pf handler Peter Xu
2021-01-15 17:09 ` [PATCH RFC 27/30] hugetlb/userfaultfd: Allow wr-protect none ptes Peter Xu
2021-01-15 17:09 ` [PATCH RFC 28/30] hugetlb/userfaultfd: Only drop uffd-wp special pte if required Peter Xu
2021-01-15 17:09 ` [PATCH RFC 29/30] userfaultfd: Enable write protection for shmem & hugetlbfs Peter Xu
2021-01-15 17:12 ` [PATCH RFC 30/30] userfaultfd/selftests: Enable uffd-wp for shmem/hugetlbfs Peter Xu
2021-01-29 22:49 ` [PATCH RFC 00/30] userfaultfd-wp: Support shmem and hugetlbfs Peter Xu
2021-02-05 21:53 ` Mike Kravetz
2021-02-06 2:36 ` Peter Xu
2021-02-09 19:29 ` Mike Kravetz
2021-02-09 22:00 ` Peter Xu
2021-02-05 22:21 ` Hugh Dickins
2021-02-06 2:47 ` Peter Xu
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