The patch titled
Subject: s390/pgtable: cleanup description of swp pte layout
has been added to the -mm tree. Its filename is
s390-pgtable-cleanup-description-of-swp-pte-layout.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/s390-pgtable-cleanup-description-of-swp-pte-layout.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/s390-pgtable-cleanup-description-of-swp-pte-layout.patch
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------------------------------------------------------
From: David Hildenbrand <david@xxxxxxxxxx>
Subject: s390/pgtable: cleanup description of swp pte layout
Bit 52 and bit 55 don't have to be zero: they only trigger a
translation-specifiation exception if the PTE is marked as valid, which is
not the case for swap ptes.
Document which bits are used for what, and which ones are unused.
Link: https://lkml.kernel.org/r/20220329164329.208407-6-david@xxxxxxxxxx
Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
Cc: Alexander Gordeev <agordeev@xxxxxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: Don Dutile <ddutile@xxxxxxxxxx>
Cc: Gerald Schaefer <gerald.schaefer@xxxxxxxxxxxxx>
Cc: Heiko Carstens <hca@xxxxxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Jan Kara <jack@xxxxxxx>
Cc: Jann Horn <jannh@xxxxxxxxxx>
Cc: Jason Gunthorpe <jgg@xxxxxxxxxx>
Cc: John Hubbard <jhubbard@xxxxxxxxxx>
Cc: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Liang Zhang <zhangliang5@xxxxxxxxxx>
Cc: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Cc: Mike Rapoport <rppt@xxxxxxxxxxxxx>
Cc: Nadav Amit <namit@xxxxxxxxxx>
Cc: Oded Gabbay <oded.gabbay@xxxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
Cc: Pedro Demarchi Gomes <pedrodemargomes@xxxxxxxxx>
Cc: Peter Xu <peterx@xxxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxxx>
Cc: Roman Gushchin <guro@xxxxxx>
Cc: Shakeel Butt <shakeelb@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Vasily Gorbik <gor@xxxxxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Will Deacon <will@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
arch/s390/include/asm/pgtable.h | 17 ++++++++---------
1 file changed, 8 insertions(+), 9 deletions(-)
--- a/arch/s390/include/asm/pgtable.h~s390-pgtable-cleanup-description-of-swp-pte-layout
+++ a/arch/s390/include/asm/pgtable.h
@@ -1712,18 +1712,17 @@ static inline int has_transparent_hugepa
/*
* 64 bit swap entry format:
* A page-table entry has some bits we have to treat in a special way.
- * Bits 52 and bit 55 have to be zero, otherwise a specification
- * exception will occur instead of a page translation exception. The
- * specification exception has the bad habit not to store necessary
- * information in the lowcore.
- * Bits 54 and 63 are used to indicate the page type.
+ * Bits 54 and 63 are used to indicate the page type. Bit 53 marks the pte
+ * as invalid.
* A swap pte is indicated by bit pattern (pte & 0x201) == 0x200
- * This leaves the bits 0-51 and bits 56-62 to store type and offset.
- * We use the 5 bits from 57-61 for the type and the 52 bits from 0-51
- * for the offset.
- * | offset |01100|type |00|
+ * | offset |X11XX|type |S0|
* |0000000000111111111122222222223333333333444444444455|55555|55566|66|
* |0123456789012345678901234567890123456789012345678901|23456|78901|23|
+ *
+ * Bits 0-51 store the offset.
+ * Bits 57-61 store the type.
+ * Bit 62 (S) is used for softdirty tracking.
+ * Bits 52, 55 and 56 (X) are unused.
*/
#define __SWP_OFFSET_MASK ((1UL << 52) - 1)
_
Patches currently in -mm which might be from david@xxxxxxxxxx are
mm-rmap-fix-missing-swap_free-in-try_to_unmap-after-arch_unmap_one-failed.patch
mm-hugetlb-take-src_mm-write_protect_seq-in-copy_hugetlb_page_range.patch
mm-memory-slightly-simplify-copy_present_pte.patch
mm-rmap-split-page_dup_rmap-into-page_dup_file_rmap-and-page_try_dup_anon_rmap.patch
mm-rmap-convert-rmap-flags-to-a-proper-distinct-rmap_t-type.patch
mm-rmap-remove-do_page_add_anon_rmap.patch
mm-rmap-pass-rmap-flags-to-hugepage_add_anon_rmap.patch
mm-rmap-drop-compound-parameter-from-page_add_new_anon_rmap.patch
mm-rmap-use-page_move_anon_rmap-when-reusing-a-mapped-pageanon-page-exclusively.patch
mm-huge_memory-remove-outdated-vm_warn_on_once_page-from-unmap_page.patch
mm-page-flags-reuse-pg_mappedtodisk-as-pg_anon_exclusive-for-pageanon-pages.patch
mm-remember-exclusively-mapped-anonymous-pages-with-pg_anon_exclusive.patch
mm-gup-disallow-follow_pagefoll_pin.patch
mm-support-gup-triggered-unsharing-of-anonymous-pages.patch
mm-gup-trigger-fault_flag_unshare-when-r-o-pinning-a-possibly-shared-anonymous-page.patch
mm-gup-sanity-check-with-config_debug_vm-that-anonymous-pages-are-exclusive-when-unpinning.patch
mm-swap-remember-pg_anon_exclusive-via-a-swp-pte-bit.patch
mm-debug_vm_pgtable-add-tests-for-__have_arch_pte_swp_exclusive.patch
x86-pgtable-support-__have_arch_pte_swp_exclusive.patch
arm64-pgtable-support-__have_arch_pte_swp_exclusive.patch
s390-pgtable-cleanup-description-of-swp-pte-layout.patch
s390-pgtable-support-__have_arch_pte_swp_exclusive.patch
powerpc-pgtable-remove-_page_bit_swap_type-for-book3s.patch
powerpc-pgtable-support-__have_arch_pte_swp_exclusive-for-book3s.patch
