linux-kernel - Re: [PATCH v1 03/13] arm64: mm: Implicitly invalidate user ASID based on TLBI operation

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Message-ID: <aUOfnXnGVROEXH4r@a079125.arm.com>
Date: Thu, 18 Dec 2025 12:00:53 +0530
From: Linu Cherian <linu.cherian@....com>
To: Ryan Roberts <ryan.roberts@....com>
Cc: Will Deacon <will@...nel.org>, Ard Biesheuvel <ardb@...nel.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Mark Rutland <mark.rutland@....com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Oliver Upton <oliver.upton@...ux.dev>,
	Marc Zyngier <maz@...nel.org>, Dev Jain <dev.jain@....com>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 03/13] arm64: mm: Implicitly invalidate user ASID
 based on TLBI operation

Ryan,

On Tue, Dec 16, 2025 at 02:45:48PM +0000, Ryan Roberts wrote:
> When kpti is enabled, separate ASIDs are used for userspace and
> kernelspace, requiring ASID-qualified TLB invalidation by virtual
> address to invalidate both of them.
> 
> Push the logic for invalidating the two ASIDs down into the low-level
> tlbi-op-specific functions and remove the burden from the caller to
> handle the kpti-specific behaviour.
> 
> Co-developed-by: Will Deacon <will@...nel.org>
> Signed-off-by: Will Deacon <will@...nel.org>
> Signed-off-by: Ryan Roberts <ryan.roberts@....com>
> ---
>  arch/arm64/include/asm/tlbflush.h | 27 ++++++++++-----------------
>  1 file changed, 10 insertions(+), 17 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/tlbflush.h b/arch/arm64/include/asm/tlbflush.h
> index c5111d2afc66..31f43d953ce2 100644
> --- a/arch/arm64/include/asm/tlbflush.h
> +++ b/arch/arm64/include/asm/tlbflush.h
> @@ -110,6 +110,7 @@ typedef void (*tlbi_op)(u64 arg);
>  static __always_inline void vae1is(u64 arg)
>  {
>  	__tlbi(vae1is, arg);
> +	__tlbi_user(vae1is, arg);
>  }
>  
>  static __always_inline void vae2is(u64 arg)
> @@ -126,6 +127,7 @@ static __always_inline void vale1(u64 arg)
>  static __always_inline void vale1is(u64 arg)
>  {
>  	__tlbi(vale1is, arg);
> +	__tlbi_user(vale1is, arg);
>  }
>  
>  static __always_inline void vale2is(u64 arg)
> @@ -162,11 +164,6 @@ static __always_inline void __tlbi_level(tlbi_op op, u64 addr, u32 level)
>  	op(arg);
>  }
>  
> -#define __tlbi_user_level(op, arg, level) do {				\
> -	if (arm64_kernel_unmapped_at_el0())				\
> -		__tlbi_level(op, (arg | USER_ASID_FLAG), level);	\
> -} while (0)
> -
>  /*
>   * This macro creates a properly formatted VA operand for the TLB RANGE. The
>   * value bit assignments are:
> @@ -435,8 +432,6 @@ static inline void arch_tlbbatch_flush(struct arch_tlbflush_unmap_batch *batch)
>   * @stride:	Flush granularity
>   * @asid:	The ASID of the task (0 for IPA instructions)
>   * @tlb_level:	Translation Table level hint, if known
> - * @tlbi_user:	If 'true', call an additional __tlbi_user()
> - *              (typically for user ASIDs). 'flase' for IPA instructions
>   * @lpa2:	If 'true', the lpa2 scheme is used as set out below
>   *
>   * When the CPU does not support TLB range operations, flush the TLB
> @@ -462,6 +457,7 @@ static inline void arch_tlbbatch_flush(struct arch_tlbflush_unmap_batch *batch)
>  static __always_inline void rvae1is(u64 arg)
>  {
>  	__tlbi(rvae1is, arg);
> +	__tlbi_user(rvae1is, arg);
>  }
>  
>  static __always_inline void rvale1(u64 arg)
> @@ -473,6 +469,7 @@ static __always_inline void rvale1(u64 arg)
>  static __always_inline void rvale1is(u64 arg)
>  {
>  	__tlbi(rvale1is, arg);
> +	__tlbi_user(rvale1is, arg);
>  }
>  
>  static __always_inline void rvaale1is(u64 arg)
> @@ -491,7 +488,7 @@ static __always_inline void __tlbi_range(tlbi_op op, u64 arg)
>  }
>  
>  #define __flush_tlb_range_op(op, start, pages, stride,			\
> -				asid, tlb_level, tlbi_user, lpa2)	\
> +				asid, tlb_level, lpa2)			\
>  do {									\
>  	typeof(start) __flush_start = start;				\
>  	typeof(pages) __flush_pages = pages;				\
> @@ -506,8 +503,6 @@ do {									\
>  		    (lpa2 && __flush_start != ALIGN(__flush_start, SZ_64K))) {	\
>  			addr = __TLBI_VADDR(__flush_start, asid);	\
>  			__tlbi_level(op, addr, tlb_level);		\
> -			if (tlbi_user)					\
> -				__tlbi_user_level(op, addr, tlb_level);	\
>  			__flush_start += stride;			\
>  			__flush_pages -= stride >> PAGE_SHIFT;		\
>  			continue;					\
> @@ -518,8 +513,6 @@ do {									\
>  			addr = __TLBI_VADDR_RANGE(__flush_start >> shift, asid, \
>  						scale, num, tlb_level);	\
>  			__tlbi_range(r##op, addr);			\
> -			if (tlbi_user)					\
> -				__tlbi_user(r##op, addr);		\
>  			__flush_start += __TLBI_RANGE_PAGES(num, scale) << PAGE_SHIFT; \
>  			__flush_pages -= __TLBI_RANGE_PAGES(num, scale);\


There are more __tlbi_user invocations in __flush_tlb_mm, __local_flush_tlb_page_nonotify_nosync
and __flush_tlb_page_nosync in this file. Should we not address them as well as 
part of this ?

--
Linu Cherian.