The patch titled
Subject: mm: lift the x86_32 PAE version of gup_get_pte to common code
has been added to the -mm tree. Its filename is
mm-lift-the-x86_32-pae-version-of-gup_get_pte-to-common-code.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-lift-the-x86_32-pae-version-of-gup_get_pte-to-common-code.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-lift-the-x86_32-pae-version-of-gup_get_pte-to-common-code.patch
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------------------------------------------------------
From: Christoph Hellwig <hch@xxxxxx>
Subject: mm: lift the x86_32 PAE version of gup_get_pte to common code
The split low/high access is the only non-READ_ONCE version of gup_get_pte
that did show up in the various arch implemenations. Lift it to common
code and drop the ifdef based arch override.
Link: http://lkml.kernel.org/r/20190625143715.1689-4-hch@xxxxxx
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
Reviewed-by: Jason Gunthorpe <jgg@xxxxxxxxxxxx>
Cc: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
Cc: David Miller <davem@xxxxxxxxxxxxx>
Cc: James Hogan <jhogan@xxxxxxxxxx>
Cc: Khalid Aziz <khalid.aziz@xxxxxxxxxx>
Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Cc: Nicholas Piggin <npiggin@xxxxxxxxx>
Cc: Paul Burton <paul.burton@xxxxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
Cc: Ralf Baechle <ralf@xxxxxxxxxxxxxx>
Cc: Rich Felker <dalias@xxxxxxxx>
Cc: Yoshinori Sato <ysato@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
arch/x86/Kconfig | 1
arch/x86/include/asm/pgtable-3level.h | 47 ----------------------
arch/x86/kvm/mmu.c | 2
mm/Kconfig | 3 +
mm/gup.c | 51 ++++++++++++++++++++++--
5 files changed, 52 insertions(+), 52 deletions(-)
--- a/arch/x86/include/asm/pgtable-3level.h~mm-lift-the-x86_32-pae-version-of-gup_get_pte-to-common-code
+++ a/arch/x86/include/asm/pgtable-3level.h
@@ -285,53 +285,6 @@ static inline pud_t native_pudp_get_and_
#define __pte_to_swp_entry(pte) (__swp_entry(__pteval_swp_type(pte), \
__pteval_swp_offset(pte)))
-#define gup_get_pte gup_get_pte
-/*
- * WARNING: only to be used in the get_user_pages_fast() implementation.
- *
- * With get_user_pages_fast(), we walk down the pagetables without taking
- * any locks. For this we would like to load the pointers atomically,
- * but that is not possible (without expensive cmpxchg8b) on PAE. What
- * we do have is the guarantee that a PTE will only either go from not
- * present to present, or present to not present or both -- it will not
- * switch to a completely different present page without a TLB flush in
- * between; something that we are blocking by holding interrupts off.
- *
- * Setting ptes from not present to present goes:
- *
- * ptep->pte_high = h;
- * smp_wmb();
- * ptep->pte_low = l;
- *
- * And present to not present goes:
- *
- * ptep->pte_low = 0;
- * smp_wmb();
- * ptep->pte_high = 0;
- *
- * We must ensure here that the load of pte_low sees 'l' iff pte_high
- * sees 'h'. We load pte_high *after* loading pte_low, which ensures we
- * don't see an older value of pte_high. *Then* we recheck pte_low,
- * which ensures that we haven't picked up a changed pte high. We might
- * have gotten rubbish values from pte_low and pte_high, but we are
- * guaranteed that pte_low will not have the present bit set *unless*
- * it is 'l'. Because get_user_pages_fast() only operates on present ptes
- * we're safe.
- */
-static inline pte_t gup_get_pte(pte_t *ptep)
-{
- pte_t pte;
-
- do {
- pte.pte_low = ptep->pte_low;
- smp_rmb();
- pte.pte_high = ptep->pte_high;
- smp_rmb();
- } while (unlikely(pte.pte_low != ptep->pte_low));
-
- return pte;
-}
-
#include <asm/pgtable-invert.h>
#endif /* _ASM_X86_PGTABLE_3LEVEL_H */
--- a/arch/x86/Kconfig~mm-lift-the-x86_32-pae-version-of-gup_get_pte-to-common-code
+++ a/arch/x86/Kconfig
@@ -121,6 +121,7 @@ config X86
select GENERIC_STRNCPY_FROM_USER
select GENERIC_STRNLEN_USER
select GENERIC_TIME_VSYSCALL
+ select GUP_GET_PTE_LOW_HIGH if X86_PAE
select HARDLOCKUP_CHECK_TIMESTAMP if X86_64
select HAVE_ACPI_APEI if ACPI
select HAVE_ACPI_APEI_NMI if ACPI
--- a/arch/x86/kvm/mmu.c~mm-lift-the-x86_32-pae-version-of-gup_get_pte-to-common-code
+++ a/arch/x86/kvm/mmu.c
@@ -650,7 +650,7 @@ static u64 __update_clear_spte_slow(u64
/*
* The idea using the light way get the spte on x86_32 guest is from
- * gup_get_pte(arch/x86/mm/gup.c).
+ * gup_get_pte (mm/gup.c).
*
* An spte tlb flush may be pending, because kvm_set_pte_rmapp
* coalesces them and we are running out of the MMU lock. Therefore
--- a/mm/gup.c~mm-lift-the-x86_32-pae-version-of-gup_get_pte-to-common-code
+++ a/mm/gup.c
@@ -1684,17 +1684,60 @@ struct page *get_dump_page(unsigned long
* This code is based heavily on the PowerPC implementation by Nick Piggin.
*/
#ifdef CONFIG_HAVE_GENERIC_GUP
+#ifdef CONFIG_GUP_GET_PTE_LOW_HIGH
+/*
+ * WARNING: only to be used in the get_user_pages_fast() implementation.
+ *
+ * With get_user_pages_fast(), we walk down the pagetables without taking any
+ * locks. For this we would like to load the pointers atomically, but sometimes
+ * that is not possible (e.g. without expensive cmpxchg8b on x86_32 PAE). What
+ * we do have is the guarantee that a PTE will only either go from not present
+ * to present, or present to not present or both -- it will not switch to a
+ * completely different present page without a TLB flush in between; something
+ * that we are blocking by holding interrupts off.
+ *
+ * Setting ptes from not present to present goes:
+ *
+ * ptep->pte_high = h;
+ * smp_wmb();
+ * ptep->pte_low = l;
+ *
+ * And present to not present goes:
+ *
+ * ptep->pte_low = 0;
+ * smp_wmb();
+ * ptep->pte_high = 0;
+ *
+ * We must ensure here that the load of pte_low sees 'l' IFF pte_high sees 'h'.
+ * We load pte_high *after* loading pte_low, which ensures we don't see an older
+ * value of pte_high. *Then* we recheck pte_low, which ensures that we haven't
+ * picked up a changed pte high. We might have gotten rubbish values from
+ * pte_low and pte_high, but we are guaranteed that pte_low will not have the
+ * present bit set *unless* it is 'l'. Because get_user_pages_fast() only
+ * operates on present ptes we're safe.
+ */
+static inline pte_t gup_get_pte(pte_t *ptep)
+{
+ pte_t pte;
+
+ do {
+ pte.pte_low = ptep->pte_low;
+ smp_rmb();
+ pte.pte_high = ptep->pte_high;
+ smp_rmb();
+ } while (unlikely(pte.pte_low != ptep->pte_low));
-#ifndef gup_get_pte
+ return pte;
+}
+#else /* CONFIG_GUP_GET_PTE_LOW_HIGH */
/*
- * We assume that the PTE can be read atomically. If this is not the case for
- * your architecture, please provide the helper.
+ * We require that the PTE can be read atomically.
*/
static inline pte_t gup_get_pte(pte_t *ptep)
{
return READ_ONCE(*ptep);
}
-#endif
+#endif /* CONFIG_GUP_GET_PTE_LOW_HIGH */
static void undo_dev_pagemap(int *nr, int nr_start, struct page **pages)
{
--- a/mm/Kconfig~mm-lift-the-x86_32-pae-version-of-gup_get_pte-to-common-code
+++ a/mm/Kconfig
@@ -762,6 +762,9 @@ config GUP_BENCHMARK
See tools/testing/selftests/vm/gup_benchmark.c
+config GUP_GET_PTE_LOW_HIGH
+ bool
+
config ARCH_HAS_PTE_SPECIAL
bool
_
Patches currently in -mm which might be from hch@xxxxxx are
mm-remove-the-account_page_dirtied-export.patch
mm-fix-an-overly-long-line-in-read_cache_page.patch
mm-dont-cast-readpage-to-filler_t-for-do_read_cache_page.patch
jffs2-pass-the-correct-prototype-to-read_cache_page.patch
9p-pass-the-correct-prototype-to-read_cache_page.patch
mm-use-untagged_addr-for-get_user_pages_fast-addresses.patch
mm-simplify-gup_fast_permitted.patch
mm-lift-the-x86_32-pae-version-of-gup_get_pte-to-common-code.patch
mips-use-the-generic-get_user_pages_fast-code.patch
sh-add-the-missing-pud_page-definition.patch
sh-use-the-generic-get_user_pages_fast-code.patch
sparc64-add-the-missing-pgd_page-definition.patch
sparc64-define-untagged_addr.patch
sparc64-use-the-generic-get_user_pages_fast-code.patch
mm-rename-config_have_generic_gup-to-config_have_fast_gup.patch
mm-reorder-code-blocks-in-gupc.patch
mm-consolidate-the-get_user_pages-implementations.patch
mm-validate-get_user_pages_fast-flags.patch
mm-move-the-powerpc-hugepd-code-to-mm-gupc.patch
mm-switch-gup_hugepte-to-use-try_get_compound_head.patch
mm-mark-the-page-referenced-in-gup_hugepte.patch
