mm/mremap: allow arch runtime override

Patch series "Speedup mremap on ppc64", v8.

This patchset enables MOVE_PMD/MOVE_PUD support on power.  This requires
the platform to support updating higher-level page tables without updating
page table entries.  This also needs to invalidate the Page Walk Cache on
architecture supporting the same.

This patch (of 3):

Architectures like ppc64 support faster mremap only with radix
translation.  Hence allow a runtime check w.r.t support for fast mremap.

Link: https://lkml.kernel.org/r/20210616045735.374532-1-aneesh.kumar@linux.ibm.com
Link: https://lkml.kernel.org/r/20210616045735.374532-2-aneesh.kumar@linux.ibm.com
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Kalesh Singh <kaleshsingh@google.com>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Kirill A. Shutemov <kirill@shutemov.name>
Cc: "Aneesh Kumar K . V" <aneesh.kumar@linux.ibm.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/arch/powerpc/include/asm/tlb.h b/arch/powerpc/include/asm/tlb.h
index 160422a..09a9ae5 100644 (file)
--- a/arch/powerpc/include/asm/tlb.h
+++ b/arch/powerpc/include/asm/tlb.h
@@ -83,5 +83,11 @@ static inline int mm_is_thread_local(struct mm_struct *mm)
 }
 #endif
 
+#define arch_supports_page_table_move arch_supports_page_table_move
+static inline bool arch_supports_page_table_move(void)
+{
+       return radix_enabled();
+}
+
 #endif /* __KERNEL__ */
 #endif /* __ASM_POWERPC_TLB_H */

diff --git a/mm/mremap.c b/mm/mremap.c
index 5236913..5989d39 100644 (file)
--- a/mm/mremap.c
+++ b/mm/mremap.c
@@ -25,7 +25,7 @@
 #include <linux/userfaultfd_k.h>
 
 #include <asm/cacheflush.h>
-#include <asm/tlbflush.h>
+#include <asm/tlb.h>
 #include <asm/pgalloc.h>
 
 #include "internal.h"
@@ -210,6 +210,15 @@ static void move_ptes(struct vm_area_struct *vma, pmd_t *old_pmd,
                drop_rmap_locks(vma);
 }
 
+#ifndef arch_supports_page_table_move
+#define arch_supports_page_table_move arch_supports_page_table_move
+static inline bool arch_supports_page_table_move(void)
+{
+       return IS_ENABLED(CONFIG_HAVE_MOVE_PMD) ||
+               IS_ENABLED(CONFIG_HAVE_MOVE_PUD);
+}
+#endif
+
 #ifdef CONFIG_HAVE_MOVE_PMD
 static bool move_normal_pmd(struct vm_area_struct *vma, unsigned long old_addr,
                  unsigned long new_addr, pmd_t *old_pmd, pmd_t *new_pmd)
@@ -218,6 +227,8 @@ static bool move_normal_pmd(struct vm_area_struct *vma, unsigned long old_addr,
        struct mm_struct *mm = vma->vm_mm;
        pmd_t pmd;
 
+       if (!arch_supports_page_table_move())
+               return false;
        /*
         * The destination pmd shouldn't be established, free_pgtables()
         * should have released it.
@@ -284,6 +295,8 @@ static bool move_normal_pud(struct vm_area_struct *vma, unsigned long old_addr,
        struct mm_struct *mm = vma->vm_mm;
        pud_t pud;
 
+       if (!arch_supports_page_table_move())
+               return false;
        /*
         * The destination pud shouldn't be established, free_pgtables()
         * should have released it.