[PATCH V3] arm64/mm: Re-organise setting up FEAT_S1PIE registers PIRE0_EL1 and PIR_EL1

[PATCH V3] arm64/mm: Re-organise setting up FEAT_S1PIE registers PIRE0_EL1 and PIR_EL1

[Anshuman Khandual]

mov_q cannot really move PIE_E[0|1] macros into a general purpose register
as expected if those macro constants contain some 128 bit layout elements,
that are required for D128 page tables. The primary issue is that for D128,
PIE_E[0|1] are defined in terms of 128-bit types with shifting and masking,
which the assembler can't accommodate.

Instead pre-calculate these PIRE0_EL1/PIR_EL1 constants into asm-offsets.h
based PIE_E0_ASM/PIE_E1_ASM which can then be used in arch/arm64/mm/proc.S.

While here also drop PTE_MAYBE_NG/PTE_MAYBE_SHARED assembly overrides which
are not required any longer, as the compiler toolchains are smart enough to
compute both the PIE_[E0|E1]_ASM constants in all scenarios.

Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
---
This patch applies on v6.15-rc4

Changes in V3:

- Dropped off macros PTE_MAYBE_NG and PTE_MAYBE_SHARED as per Ryan

Changes in V2:

https://lore.kernel.org/all/20250416035604.2717188-1-anshuman.khandual@arm.com/

- Added asm-offsets.c based PIE_E0_ASM and PIE_E1_ASM symbols as per Ard
- Moved PTE_MAYBE_NG and PTE_MAYBE_SHARED overrides inside asm-offsets.c
  along with the corresponding comment as per Ard

Changes in V1:

https://lore.kernel.org/linux-arm-kernel/20250410074024.1545768-1-anshuman.khandual@arm.com/

 arch/arm64/kernel/asm-offsets.c |  2 ++
 arch/arm64/mm/proc.S            | 19 ++-----------------
 2 files changed, 4 insertions(+), 17 deletions(-)

diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
index eb1a840e4110..30d4bbe68661 100644
--- a/arch/arm64/kernel/asm-offsets.c
+++ b/arch/arm64/kernel/asm-offsets.c
@@ -182,5 +182,7 @@ int main(void)
 #ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
   DEFINE(FTRACE_OPS_DIRECT_CALL,	offsetof(struct ftrace_ops, direct_call));
 #endif
+  DEFINE(PIE_E0_ASM, PIE_E0);
+  DEFINE(PIE_E1_ASM, PIE_E1);
   return 0;
 }
diff --git a/arch/arm64/mm/proc.S b/arch/arm64/mm/proc.S
index fb30c8804f87..80d470aa469d 100644
--- a/arch/arm64/mm/proc.S
+++ b/arch/arm64/mm/proc.S
@@ -512,26 +512,11 @@ alternative_else_nop_endif
 	ubfx	x1, x1, #ID_AA64MMFR3_EL1_S1PIE_SHIFT, #4
 	cbz	x1, .Lskip_indirection
 
-	/*
-	 * The PROT_* macros describing the various memory types may resolve to
-	 * C expressions if they include the PTE_MAYBE_* macros, and so they
-	 * can only be used from C code. The PIE_E* constants below are also
-	 * defined in terms of those macros, but will mask out those
-	 * PTE_MAYBE_* constants, whether they are set or not. So #define them
-	 * as 0x0 here so we can evaluate the PIE_E* constants in asm context.
-	 */
-
-#define PTE_MAYBE_NG		0
-#define PTE_MAYBE_SHARED	0
-
-	mov_q	x0, PIE_E0
+	mov_q	x0, PIE_E0_ASM
 	msr	REG_PIRE0_EL1, x0
-	mov_q	x0, PIE_E1
+	mov_q	x0, PIE_E1_ASM
 	msr	REG_PIR_EL1, x0
 
-#undef PTE_MAYBE_NG
-#undef PTE_MAYBE_SHARED
-
 	orr	tcr2, tcr2, TCR2_EL1_PIE
 	msr	REG_TCR2_EL1, x0
 
-- 
2.25.1

Re: [PATCH V3] arm64/mm: Re-organise setting up FEAT_S1PIE registers PIRE0_EL1 and PIR_EL1

[Anshuman Khandual]

On 4/29/25 10:35, Anshuman Khandual wrote:
> mov_q cannot really move PIE_E[0|1] macros into a general purpose register
> as expected if those macro constants contain some 128 bit layout elements,
> that are required for D128 page tables. The primary issue is that for D128,
> PIE_E[0|1] are defined in terms of 128-bit types with shifting and masking,
> which the assembler can't accommodate.
> 
> Instead pre-calculate these PIRE0_EL1/PIR_EL1 constants into asm-offsets.h
> based PIE_E0_ASM/PIE_E1_ASM which can then be used in arch/arm64/mm/proc.S.
> 
> While here also drop PTE_MAYBE_NG/PTE_MAYBE_SHARED assembly overrides which
> are not required any longer, as the compiler toolchains are smart enough to
> compute both the PIE_[E0|E1]_ASM constants in all scenarios.
> 
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Will Deacon <will@kernel.org>
> Cc: Mark Rutland <mark.rutland@arm.com>
> Cc: Ard Biesheuvel <ardb@kernel.org>
> Cc: Ryan Roberts <ryan.roberts@arm.com>
> Cc: linux-arm-kernel@lists.infradead.org
> Cc: linux-kernel@vger.kernel.org
> Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
> ---
> This patch applies on v6.15-rc4

Gentle ping, any updates on this.

> 
> Changes in V3:
> 
> - Dropped off macros PTE_MAYBE_NG and PTE_MAYBE_SHARED as per Ryan
> 
> Changes in V2:
> 
> https://lore.kernel.org/all/20250416035604.2717188-1-anshuman.khandual@arm.com/
> 
> - Added asm-offsets.c based PIE_E0_ASM and PIE_E1_ASM symbols as per Ard
> - Moved PTE_MAYBE_NG and PTE_MAYBE_SHARED overrides inside asm-offsets.c
>   along with the corresponding comment as per Ard
> 
> Changes in V1:
> 
> https://lore.kernel.org/linux-arm-kernel/20250410074024.1545768-1-anshuman.khandual@arm.com/
> 
>  arch/arm64/kernel/asm-offsets.c |  2 ++
>  arch/arm64/mm/proc.S            | 19 ++-----------------
>  2 files changed, 4 insertions(+), 17 deletions(-)
> 
> diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
> index eb1a840e4110..30d4bbe68661 100644
> --- a/arch/arm64/kernel/asm-offsets.c
> +++ b/arch/arm64/kernel/asm-offsets.c
> @@ -182,5 +182,7 @@ int main(void)
>  #ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
>    DEFINE(FTRACE_OPS_DIRECT_CALL,	offsetof(struct ftrace_ops, direct_call));
>  #endif
> +  DEFINE(PIE_E0_ASM, PIE_E0);
> +  DEFINE(PIE_E1_ASM, PIE_E1);
>    return 0;
>  }
> diff --git a/arch/arm64/mm/proc.S b/arch/arm64/mm/proc.S
> index fb30c8804f87..80d470aa469d 100644
> --- a/arch/arm64/mm/proc.S
> +++ b/arch/arm64/mm/proc.S
> @@ -512,26 +512,11 @@ alternative_else_nop_endif
>  	ubfx	x1, x1, #ID_AA64MMFR3_EL1_S1PIE_SHIFT, #4
>  	cbz	x1, .Lskip_indirection
>  
> -	/*
> -	 * The PROT_* macros describing the various memory types may resolve to
> -	 * C expressions if they include the PTE_MAYBE_* macros, and so they
> -	 * can only be used from C code. The PIE_E* constants below are also
> -	 * defined in terms of those macros, but will mask out those
> -	 * PTE_MAYBE_* constants, whether they are set or not. So #define them
> -	 * as 0x0 here so we can evaluate the PIE_E* constants in asm context.
> -	 */
> -
> -#define PTE_MAYBE_NG		0
> -#define PTE_MAYBE_SHARED	0
> -
> -	mov_q	x0, PIE_E0
> +	mov_q	x0, PIE_E0_ASM
>  	msr	REG_PIRE0_EL1, x0
> -	mov_q	x0, PIE_E1
> +	mov_q	x0, PIE_E1_ASM
>  	msr	REG_PIR_EL1, x0
>  
> -#undef PTE_MAYBE_NG
> -#undef PTE_MAYBE_SHARED
> -
>  	orr	tcr2, tcr2, TCR2_EL1_PIE
>  	msr	REG_TCR2_EL1, x0
>  

Re: [PATCH V3] arm64/mm: Re-organise setting up FEAT_S1PIE registers PIRE0_EL1 and PIR_EL1

[Ryan Roberts]

On 29/04/2025 06:05, Anshuman Khandual wrote:
> mov_q cannot really move PIE_E[0|1] macros into a general purpose register
> as expected if those macro constants contain some 128 bit layout elements,
> that are required for D128 page tables. The primary issue is that for D128,
> PIE_E[0|1] are defined in terms of 128-bit types with shifting and masking,
> which the assembler can't accommodate.
> 
> Instead pre-calculate these PIRE0_EL1/PIR_EL1 constants into asm-offsets.h
> based PIE_E0_ASM/PIE_E1_ASM which can then be used in arch/arm64/mm/proc.S.
> 
> While here also drop PTE_MAYBE_NG/PTE_MAYBE_SHARED assembly overrides which
> are not required any longer, as the compiler toolchains are smart enough to
> compute both the PIE_[E0|E1]_ASM constants in all scenarios.
> 
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Will Deacon <will@kernel.org>
> Cc: Mark Rutland <mark.rutland@arm.com>
> Cc: Ard Biesheuvel <ardb@kernel.org>
> Cc: Ryan Roberts <ryan.roberts@arm.com>
> Cc: linux-arm-kernel@lists.infradead.org
> Cc: linux-kernel@vger.kernel.org
> Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>

Reviewed-by: Ryan Roberts <ryan.roberts@arm.com>

> ---
> This patch applies on v6.15-rc4
> 
> Changes in V3:
> 
> - Dropped off macros PTE_MAYBE_NG and PTE_MAYBE_SHARED as per Ryan
> 
> Changes in V2:
> 
> https://lore.kernel.org/all/20250416035604.2717188-1-anshuman.khandual@arm.com/
> 
> - Added asm-offsets.c based PIE_E0_ASM and PIE_E1_ASM symbols as per Ard
> - Moved PTE_MAYBE_NG and PTE_MAYBE_SHARED overrides inside asm-offsets.c
>   along with the corresponding comment as per Ard
> 
> Changes in V1:
> 
> https://lore.kernel.org/linux-arm-kernel/20250410074024.1545768-1-anshuman.khandual@arm.com/
> 
>  arch/arm64/kernel/asm-offsets.c |  2 ++
>  arch/arm64/mm/proc.S            | 19 ++-----------------
>  2 files changed, 4 insertions(+), 17 deletions(-)
> 
> diff --git a/arch/arm64/kernel/asm-offsets.c b/arch/arm64/kernel/asm-offsets.c
> index eb1a840e4110..30d4bbe68661 100644
> --- a/arch/arm64/kernel/asm-offsets.c
> +++ b/arch/arm64/kernel/asm-offsets.c
> @@ -182,5 +182,7 @@ int main(void)
>  #ifdef CONFIG_DYNAMIC_FTRACE_WITH_DIRECT_CALLS
>    DEFINE(FTRACE_OPS_DIRECT_CALL,	offsetof(struct ftrace_ops, direct_call));
>  #endif
> +  DEFINE(PIE_E0_ASM, PIE_E0);
> +  DEFINE(PIE_E1_ASM, PIE_E1);
>    return 0;
>  }
> diff --git a/arch/arm64/mm/proc.S b/arch/arm64/mm/proc.S
> index fb30c8804f87..80d470aa469d 100644
> --- a/arch/arm64/mm/proc.S
> +++ b/arch/arm64/mm/proc.S
> @@ -512,26 +512,11 @@ alternative_else_nop_endif
>  	ubfx	x1, x1, #ID_AA64MMFR3_EL1_S1PIE_SHIFT, #4
>  	cbz	x1, .Lskip_indirection
>  
> -	/*
> -	 * The PROT_* macros describing the various memory types may resolve to
> -	 * C expressions if they include the PTE_MAYBE_* macros, and so they
> -	 * can only be used from C code. The PIE_E* constants below are also
> -	 * defined in terms of those macros, but will mask out those
> -	 * PTE_MAYBE_* constants, whether they are set or not. So #define them
> -	 * as 0x0 here so we can evaluate the PIE_E* constants in asm context.
> -	 */
> -
> -#define PTE_MAYBE_NG		0
> -#define PTE_MAYBE_SHARED	0
> -
> -	mov_q	x0, PIE_E0
> +	mov_q	x0, PIE_E0_ASM
>  	msr	REG_PIRE0_EL1, x0
> -	mov_q	x0, PIE_E1
> +	mov_q	x0, PIE_E1_ASM
>  	msr	REG_PIR_EL1, x0
>  
> -#undef PTE_MAYBE_NG
> -#undef PTE_MAYBE_SHARED
> -
>  	orr	tcr2, tcr2, TCR2_EL1_PIE
>  	msr	REG_TCR2_EL1, x0
>  

Re: [PATCH V3] arm64/mm: Re-organise setting up FEAT_S1PIE registers PIRE0_EL1 and PIR_EL1

[Will Deacon]

On Tue, 29 Apr 2025 10:35:11 +0530, Anshuman Khandual wrote:
> mov_q cannot really move PIE_E[0|1] macros into a general purpose register
> as expected if those macro constants contain some 128 bit layout elements,
> that are required for D128 page tables. The primary issue is that for D128,
> PIE_E[0|1] are defined in terms of 128-bit types with shifting and masking,
> which the assembler can't accommodate.
> 
> Instead pre-calculate these PIRE0_EL1/PIR_EL1 constants into asm-offsets.h
> based PIE_E0_ASM/PIE_E1_ASM which can then be used in arch/arm64/mm/proc.S.
> 
> [...]

Applied to arm64 (for-next/entry), thanks!

[1/1] arm64/mm: Re-organise setting up FEAT_S1PIE registers PIRE0_EL1 and PIR_EL1
      https://git.kernel.org/arm64/c/29e31da4ed26

Cheers,
-- 
Will

https://fixes.arm64.dev
https://next.arm64.dev
https://will.arm64.dev