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

[Qi Zheng <qi.zheng@linux.dev>]

On 1/28/26 4:46 AM, Andrew Morton wrote:
> On Tue, 27 Jan 2026 20:12:53 +0800 Qi Zheng <qi.zheng@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.
> _
>