From: Catalin Marinas <catalin.marinas@arm.com>
To: David Hildenbrand <david@redhat.com>
Cc: x86@kernel.org, Jan Kara <jack@suse.cz>,
Yang Shi <shy828301@gmail.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
Peter Xu <peterx@redhat.com>, Michal Hocko <mhocko@kernel.org>,
linux-mm@kvack.org, Donald Dutile <ddutile@redhat.com>,
Liang Zhang <zhangliang5@huawei.com>,
Borislav Petkov <bp@alien8.de>,
Alexander Gordeev <agordeev@linux.ibm.com>,
Will Deacon <will@kernel.org>, Christoph Hellwig <hch@lst.de>,
Paul Mackerras <paulus@samba.org>,
Andrea Arcangeli <aarcange@redhat.com>,
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Mike Rapoport <rppt@linux.ibm.com>,
Ingo Molnar <mingo@redhat.com>,
linux-arm-kernel@lists.infradead.org,
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Shakeel Butt <shakeelb@google.com>,
Oleg Nesterov <oleg@redhat.com>,
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Oded Gabbay <oded.gabbay@gmail.com>,
linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org,
Nadav Amit <namit@vmware.com>,
Andrew Morton <akpm@linux-foundation.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
Roman Gushchin <guro@fb.com>,
"Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
Mike Kravetz <mike.kravetz@oracle.com>
Subject: Re: [PATCH v1 4/7] arm64/pgtable: support __HAVE_ARCH_PTE_SWP_EXCLUSIVE
Date: Wed, 16 Mar 2022 18:27:01 +0000 [thread overview]
Message-ID: <YjIr9f9qaz4xITVd@arm.com> (raw)
In-Reply-To: <20220315141837.137118-5-david@redhat.com>
On Tue, Mar 15, 2022 at 03:18:34PM +0100, David Hildenbrand wrote:
> diff --git a/arch/arm64/include/asm/pgtable-prot.h b/arch/arm64/include/asm/pgtable-prot.h
> index b1e1b74d993c..62e0ebeed720 100644
> --- a/arch/arm64/include/asm/pgtable-prot.h
> +++ b/arch/arm64/include/asm/pgtable-prot.h
> @@ -14,6 +14,7 @@
> * Software defined PTE bits definition.
> */
> #define PTE_WRITE (PTE_DBM) /* same as DBM (51) */
> +#define PTE_SWP_EXCLUSIVE (_AT(pteval_t, 1) << 2) /* only for swp ptes */
I think we can use bit 1 here.
> @@ -909,12 +925,13 @@ static inline pmd_t pmdp_establish(struct vm_area_struct *vma,
> /*
> * Encode and decode a swap entry:
> * bits 0-1: present (must be zero)
> - * bits 2-7: swap type
> + * bits 2: remember PG_anon_exclusive
> + * bits 3-7: swap type
> * bits 8-57: swap offset
> * bit 58: PTE_PROT_NONE (must be zero)
I don't remember exactly why we reserved bits 0 and 1 when, from the
hardware perspective, it's sufficient for bit 0 to be 0 and the whole
pte becomes invalid. We use bit 1 as the 'table' bit (when 0 at pmd
level, it's a huge page) but we shouldn't check for this on a swap
entry.
--
Catalin
next prev parent reply other threads:[~2022-03-16 18:27 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-15 14:18 [PATCH v1 0/7] mm: COW fixes part 3: reliable GUP R/W FOLL_GET of anonymous pages David Hildenbrand
2022-03-15 14:18 ` [PATCH v1 1/7] mm/swap: remember PG_anon_exclusive via a swp pte bit David Hildenbrand
2022-03-15 14:18 ` [PATCH v1 2/7] mm/debug_vm_pgtable: add tests for __HAVE_ARCH_PTE_SWP_EXCLUSIVE David Hildenbrand
2022-03-15 14:18 ` [PATCH v1 3/7] x86/pgtable: support __HAVE_ARCH_PTE_SWP_EXCLUSIVE David Hildenbrand
2022-03-15 14:18 ` [PATCH v1 4/7] arm64/pgtable: " David Hildenbrand
2022-03-16 18:27 ` Catalin Marinas [this message]
2022-03-17 10:04 ` David Hildenbrand
2022-03-17 17:58 ` Catalin Marinas
2022-03-18 9:59 ` David Hildenbrand
2022-03-18 11:33 ` Catalin Marinas
2022-03-18 14:14 ` David Hildenbrand
2022-03-21 14:38 ` Will Deacon
2022-03-21 14:39 ` Will Deacon
2022-03-21 15:07 ` David Hildenbrand
2022-03-21 17:44 ` Will Deacon
2022-03-21 18:27 ` Catalin Marinas
2022-03-22 9:46 ` David Hildenbrand
2022-03-15 14:18 ` [PATCH v1 5/7] s390/pgtable: " David Hildenbrand
2022-03-15 16:21 ` Gerald Schaefer
2022-03-15 16:37 ` David Hildenbrand
2022-03-15 16:58 ` David Hildenbrand
2022-03-15 17:12 ` David Hildenbrand
2022-03-15 17:14 ` David Hildenbrand
2022-03-16 10:56 ` Gerald Schaefer
2022-03-16 11:06 ` David Hildenbrand
2022-03-16 13:01 ` Christian Borntraeger
2022-03-16 13:27 ` Gerald Schaefer
2022-03-16 14:00 ` David Hildenbrand
2022-03-15 14:18 ` [PATCH v1 6/7] powerpc/pgtable: remove _PAGE_BIT_SWAP_TYPE for book3s David Hildenbrand
2022-03-15 14:18 ` [PATCH v1 7/7] powerpc/pgtable: support __HAVE_ARCH_PTE_SWP_EXCLUSIVE " David Hildenbrand
2022-03-18 23:48 ` [PATCH v1 0/7] mm: COW fixes part 3: reliable GUP R/W FOLL_GET of anonymous pages Jason Gunthorpe
2022-03-19 11:17 ` David Hildenbrand
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