Re: [PATCH v4 0/8] enable PT_RECLAIM on more 64-bit architectures

[Qi Zheng]

On 1/28/26 4:46 AM, Andrew Morton wrote:

On Tue, 27 Jan 2026 20:12:53 +0800 Qi Zheng <qi.zh...@linux.dev> wrote:

This series aims to enable PT_RECLAIM on more 64-bit architectures.

Thanks, I updated mm.git's mm-unstable branch to v4.

Changes in v4:
  - convert __HAVE_ARCH_TLB_REMOVE_TABLE to CONFIG_HAVE_ARCH_TLB_REMOVE_TABLE 
config
  - fix a WARN_ON_ONCE() on sparc64 (and on ppc)
    (reported by Andreas Larsson)
  - collect Acked-by (Hi David, I've kept your Acked-by, feel free to drop it)
  - rebase onto the v6.19-rc7

Below is how v4 altered mm.git.

I'm not seeing the WARN_ON_ONCE() fix.  I assume that was due to the
Kconfig alterations?

Yes, sparc64 and ppc will select HAVE_ARCH_TLB_REMOVE_TABLE, so
PT_RECLAIM will not be enabled. This means it won't affect
sparc64 and ppc, and will not trigger WARN_ON_ONCE().

I don't have a testing environment for sparc64 and ppc, but I
expect it should be able to fix the WARN_ON_ONCE().

Thanks,
Qi

--- a/arch/powerpc/include/asm/tlb.h~b
+++ a/arch/powerpc/include/asm/tlb.h
@@ -37,7 +37,6 @@ extern void tlb_flush(struct mmu_gather
   */
  #define tlb_needs_table_invalidate()  radix_enabled()

-#define __HAVE_ARCH_TLB_REMOVE_TABLE

  /* Get the generic bits... */
  #include <asm-generic/tlb.h>

--- a/arch/powerpc/Kconfig~b

+++ a/arch/powerpc/Kconfig
@@ -305,6 +305,7 @@ config PPC
        select LOCK_MM_AND_FIND_VMA
        select MMU_GATHER_PAGE_SIZE
        select MMU_GATHER_RCU_TABLE_FREE
+       select HAVE_ARCH_TLB_REMOVE_TABLE
        select MMU_GATHER_MERGE_VMAS
        select MMU_LAZY_TLB_SHOOTDOWN           if PPC_BOOK3S_64
        select MODULES_USE_ELF_RELA
--- a/arch/sparc/include/asm/tlb_64.h~b
+++ a/arch/sparc/include/asm/tlb_64.h
@@ -33,7 +33,6 @@ void flush_tlb_pending(void);
  #define tlb_needs_table_invalidate()  (false)
  #endif

-#define __HAVE_ARCH_TLB_REMOVE_TABLE

  #include <asm-generic/tlb.h>

#endif /* _SPARC64_TLB_H */

--- a/arch/sparc/Kconfig~b
+++ a/arch/sparc/Kconfig
@@ -74,6 +74,7 @@ config SPARC64
        select HAVE_KRETPROBES
        select HAVE_KPROBES
        select MMU_GATHER_RCU_TABLE_FREE if SMP
+       select HAVE_ARCH_TLB_REMOVE_TABLE if SMP
        select MMU_GATHER_MERGE_VMAS
        select MMU_GATHER_NO_FLUSH_CACHE
        select HAVE_ARCH_TRANSPARENT_HUGEPAGE
--- a/include/asm-generic/tlb.h~b
+++ a/include/asm-generic/tlb.h
@@ -213,7 +213,7 @@ struct mmu_table_batch {
  #define MAX_TABLE_BATCH               \
        ((PAGE_SIZE - sizeof(struct mmu_table_batch)) / sizeof(void *))

-#ifndef __HAVE_ARCH_TLB_REMOVE_TABLE

+#ifndef CONFIG_HAVE_ARCH_TLB_REMOVE_TABLE
  static inline void __tlb_remove_table(void *table)
  {
        struct ptdesc *ptdesc = (struct ptdesc *)table;
--- a/mm/Kconfig~b
+++ a/mm/Kconfig
@@ -1448,9 +1448,12 @@ config ARCH_HAS_USER_SHADOW_STACK
          The architecture has hardware support for userspace shadow call
            stacks (eg, x86 CET, arm64 GCS or RISC-V Zicfiss).

+config HAVE_ARCH_TLB_REMOVE_TABLE

+       def_bool n
+
  config PT_RECLAIM
        def_bool y
-       depends on MMU_GATHER_RCU_TABLE_FREE
+       depends on MMU_GATHER_RCU_TABLE_FREE && !HAVE_ARCH_TLB_REMOVE_TABLE
        help
          Try to reclaim empty user page table pages in paths other than munmap
          and exit_mmap path.
_