mm/mglru: add CONFIG_ARCH_HAS_HW_PTE_YOUNG

Patch series "mm/mglru: Kconfig cleanup", v4.

This series is the result of the following discussion:
https://lore.kernel.org/47066176-bd93-55dd-c2fa-002299d9e034@linux.ibm.com/

It mainly avoids building the code that walks page tables on CPUs that
use it, i.e., those don't support hardware accessed bit. Specifically,
it introduces a new Kconfig to guard some of functions added by
commit bd74fdaea146 ("mm: multi-gen LRU: support page table walks")
on CPUs like POWER9, on which the series was tested.

This patch (of 5):

Some architectures are able to set the accessed bit in PTEs when PTEs
are used as part of linear address translations.

Add CONFIG_ARCH_HAS_HW_PTE_YOUNG for such architectures to be able to
override arch_has_hw_pte_young().

Link: https://lkml.kernel.org/r/20231227141205.2200125-1-kinseyho@google.com
Link: https://lkml.kernel.org/r/20231227141205.2200125-2-kinseyho@google.com
Signed-off-by: Kinsey Ho <kinseyho@google.com>
Co-developed-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Tested-by: Donet Tom <donettom@linux.vnet.ibm.com>
Acked-by: Yu Zhao <yuzhao@google.com>
Cc: kernel test robot <lkp@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/arch/Kconfig b/arch/Kconfig
index f4b210a..8c8901f 100644 (file)
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -1470,6 +1470,14 @@ config DYNAMIC_SIGFRAME
 config HAVE_ARCH_NODE_DEV_GROUP
        bool
 
+config ARCH_HAS_HW_PTE_YOUNG
+       bool
+       help
+         Architectures that select this option are capable of setting the
+         accessed bit in PTE entries when using them as part of linear address
+         translations. Architectures that require runtime check should select
+         this option and override arch_has_hw_pte_young().
+
 config ARCH_HAS_NONLEAF_PMD_YOUNG
        bool
        help

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 7b071a0..12d611f 100644 (file)
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -36,6 +36,7 @@ config ARM64
        select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
        select ARCH_HAS_PTE_DEVMAP
        select ARCH_HAS_PTE_SPECIAL
+       select ARCH_HAS_HW_PTE_YOUNG
        select ARCH_HAS_SETUP_DMA_OPS
        select ARCH_HAS_SET_DIRECT_MAP
        select ARCH_HAS_SET_MEMORY

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 1566748..04941a1 100644 (file)
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -88,6 +88,7 @@ config X86
        select ARCH_HAS_PMEM_API                if X86_64
        select ARCH_HAS_PTE_DEVMAP              if X86_64
        select ARCH_HAS_PTE_SPECIAL
+       select ARCH_HAS_HW_PTE_YOUNG
        select ARCH_HAS_NONLEAF_PMD_YOUNG       if PGTABLE_LEVELS > 2
        select ARCH_HAS_UACCESS_FLUSHCACHE      if X86_64
        select ARCH_HAS_COPY_MC                 if X86_64

diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
index 57bab91..08b5cb2 100644 (file)
--- a/arch/x86/include/asm/pgtable.h
+++ b/arch/x86/include/asm/pgtable.h
@@ -1679,12 +1679,6 @@ static inline bool arch_has_pfn_modify_check(void)
        return boot_cpu_has_bug(X86_BUG_L1TF);
 }
 
-#define arch_has_hw_pte_young arch_has_hw_pte_young
-static inline bool arch_has_hw_pte_young(void)
-{
-       return true;
-}
-
 #define arch_check_zapped_pte arch_check_zapped_pte
 void arch_check_zapped_pte(struct vm_area_struct *vma, pte_t pte);
 

diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
index af7639c..9ecc20f 100644 (file)
--- a/include/linux/pgtable.h
+++ b/include/linux/pgtable.h
@@ -375,7 +375,7 @@ static inline bool arch_has_hw_nonleaf_pmd_young(void)
  */
 static inline bool arch_has_hw_pte_young(void)
 {
-       return false;
+       return IS_ENABLED(CONFIG_ARCH_HAS_HW_PTE_YOUNG);
 }
 #endif