[Devel] [PATCH RHEL8 COMMIT] ms/mm: select HAVE_MOVE_PMD on x86 for faster mremap

[Konstantin Khorenko]

The commit is pushed to "branch-rh8-4.18.0-240.1.1.vz8.5.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh8-4.18.0-240.1.1.vz8.5.40
------>
commit 08468bdadbe7042787f9c2e8d6cbd6e2e266be90
Author: Joel Fernandes (Google) <joel at joelfernandes.org>
Date:   Fri Jun 11 15:08:02 2021 +0300

    ms/mm: select HAVE_MOVE_PMD on x86 for faster mremap
    
    Moving page-tables at the PMD-level on x86 is known to be safe.  Enable
    this option so that we can do fast mremap when possible.
    
    Link: http://lkml.kernel.org/r/20181108181201.88826-4-joelaf@google.com
    Signed-off-by: Joel Fernandes (Google) <joel at joelfernandes.org>
    Suggested-by: Kirill A. Shutemov <kirill at shutemov.name>
    Acked-by: Kirill A. Shutemov <kirill at shutemov.name>
    Cc: Julia Lawall <Julia.Lawall at lip6.fr>
    Cc: Michal Hocko <mhocko at kernel.org>
    Cc: William Kucharski <william.kucharski at oracle.com>
    Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
    Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
    
    (cherry picked from commit 9f132f7e145506efc0744426cb338b18a54afc3b)
    Signed-off-by: Kirill Tkhai <ktkhai at virtuozzo.com>
    
    Patchset description:
    
    Patch "mm: speed up mremap by 20x on large regions" introduces
    optimization: when a moved region has source and destination addresses
    and size equal to multiple of PMD_SIZE; PTEs are not really copyed.
    Instead of this, new PMD pointer is changed to point to old PTEs, while
    old PMD is cleared.
    
    This may be useful, when CRIU remaps large memory areas on restore (but
    really, alignment to PMD_SIZE is not very often, though possible).
    
    (cherry-picked from ms 9f132f7e145506efc0744426cb338b18a54afc3b)
    Signed-off-by: Andrey Zhadchenko <andrey.zhadchenko at virtuozzo.com>
---
 arch/x86/Kconfig | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index d90d31ecd054..fb2207657707 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -186,6 +186,7 @@ config X86
 	select HAVE_MEMBLOCK_NODE_MAP
 	select HAVE_MIXED_BREAKPOINTS_REGS
 	select HAVE_MOD_ARCH_SPECIFIC
+	select HAVE_MOVE_PMD
 	select HAVE_NMI
 	select HAVE_OPROFILE
 	select HAVE_OPTPROBES