[PATCH 0/2] arm64 lpa2 fixes

[PATCH 0/2] arm64 lpa2 fixes

[Ard Biesheuvel]

From: Ard Biesheuvel <ardb@kernel.org>

A couple of fixes for the LPA2 code queued up in arm64/for-next.


Ard Biesheuvel (2):
  arm64/mm: Use generic __pud_free() helper in pud_free() implementation
  arm64/mm: Avoid ID mapping of kpti flag if it is no longer needed

 arch/arm64/include/asm/pgalloc.h | 3 +--
 arch/arm64/mm/mmu.c              | 2 +-
 2 files changed, 2 insertions(+), 3 deletions(-)

-- 
2.44.0.278.ge034bb2e1d-goog


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[PATCH 1/2] arm64/mm: Use generic __pud_free() helper in pud_free() implementation

[Ard Biesheuvel]

From: Ard Biesheuvel <ardb@kernel.org>

Commit 0dd4f60a2c76 ("arm64: mm: Add support for folding PUDs at
runtime") implements specialized PUD alloc/free helpers to allow the
decision whether or not to fold PUDs to be made at runtime when the
number of paging levels is 4 or higher.

Its implementation of pud_free() is based on the generic version that
existed when the patch was first written, but in the meantime, the
freeing of a PUD has become a bit more involved, and so instead of
simply freeing the page, we should invoke the generic __pud_free() that
encapsulates whatever needs doing at this point.

This fixes a reported warning emitted by the page flags
self-diagnostics.

Reported-by: Ryan Roberts <ryan.roberts@arm.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 arch/arm64/include/asm/pgalloc.h | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/arch/arm64/include/asm/pgalloc.h b/arch/arm64/include/asm/pgalloc.h
index aeba2cf15a25..8ff5f2a2579e 100644
--- a/arch/arm64/include/asm/pgalloc.h
+++ b/arch/arm64/include/asm/pgalloc.h
@@ -60,8 +60,7 @@ static inline void pud_free(struct mm_struct *mm, pud_t *pud)
 {
 	if (!pgtable_l4_enabled())
 		return;
-	BUG_ON((unsigned long)pud & (PAGE_SIZE-1));
-	free_page((unsigned long)pud);
+	__pud_free(mm, pud);
 }
 #else
 static inline void __p4d_populate(p4d_t *p4dp, phys_addr_t pudp, p4dval_t prot)
-- 
2.44.0.278.ge034bb2e1d-goog


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[PATCH 2/2] arm64/mm: Avoid ID mapping of kpti flag if it is no longer needed

[Ard Biesheuvel]

From: Ard Biesheuvel <ardb@kernel.org>

arm64_use_ng_mappings will be set to 'true' by the early boot code if it
decides to use non-global (nG) attributes for all kernel mappings,
typically when enabling KASLR on a system that does not implement E0PD.

In this case, the G-to-nG update routines are never called, and so there
is no reason to create the writable mapping of the associated status
flag in the ID map.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
---
 arch/arm64/mm/mmu.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index b131ed31a6c8..bf5b1c426ad0 100644
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -777,7 +777,7 @@ static void __init create_idmap(void)
 		       IDMAP_ROOT_LEVEL, (pte_t *)idmap_pg_dir, false,
 		       __phys_to_virt(ptep) - ptep);
 
-	if (IS_ENABLED(CONFIG_UNMAP_KERNEL_AT_EL0)) {
+	if (IS_ENABLED(CONFIG_UNMAP_KERNEL_AT_EL0) && !arm64_use_ng_mappings) {
 		extern u32 __idmap_kpti_flag;
 		u64 pa = __pa_symbol(&__idmap_kpti_flag);
 
-- 
2.44.0.278.ge034bb2e1d-goog


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Re: [PATCH 1/2] arm64/mm: Use generic __pud_free() helper in pud_free() implementation

[Ryan Roberts]

On 01/03/2024 10:40, Ard Biesheuvel wrote:
> From: Ard Biesheuvel <ardb@kernel.org>
> 
> Commit 0dd4f60a2c76 ("arm64: mm: Add support for folding PUDs at
> runtime") implements specialized PUD alloc/free helpers to allow the
> decision whether or not to fold PUDs to be made at runtime when the
> number of paging levels is 4 or higher.
> 
> Its implementation of pud_free() is based on the generic version that
> existed when the patch was first written, but in the meantime, the
> freeing of a PUD has become a bit more involved, and so instead of
> simply freeing the page, we should invoke the generic __pud_free() that
> encapsulates whatever needs doing at this point.
> 
> This fixes a reported warning emitted by the page flags
> self-diagnostics.
> 
> Reported-by: Ryan Roberts <ryan.roberts@arm.com>
> Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

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

> ---
>  arch/arm64/include/asm/pgalloc.h | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/pgalloc.h b/arch/arm64/include/asm/pgalloc.h
> index aeba2cf15a25..8ff5f2a2579e 100644
> --- a/arch/arm64/include/asm/pgalloc.h
> +++ b/arch/arm64/include/asm/pgalloc.h
> @@ -60,8 +60,7 @@ static inline void pud_free(struct mm_struct *mm, pud_t *pud)
>  {
>  	if (!pgtable_l4_enabled())
>  		return;
> -	BUG_ON((unsigned long)pud & (PAGE_SIZE-1));
> -	free_page((unsigned long)pud);
> +	__pud_free(mm, pud);
>  }
>  #else
>  static inline void __p4d_populate(p4d_t *p4dp, phys_addr_t pudp, p4dval_t prot)


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Re: [PATCH 0/2] arm64 lpa2 fixes

[Catalin Marinas]

On Fri, 01 Mar 2024 11:40:47 +0100, Ard Biesheuvel wrote:
> A couple of fixes for the LPA2 code queued up in arm64/for-next.
> 
> 
> Ard Biesheuvel (2):
>   arm64/mm: Use generic __pud_free() helper in pud_free() implementation
>   arm64/mm: Avoid ID mapping of kpti flag if it is no longer needed
> 
> [...]

Applied to arm64 (for-next/stage1-lpa2), thanks!

[1/2] arm64/mm: Use generic __pud_free() helper in pud_free() implementation
      https://git.kernel.org/arm64/c/3137db4c66bf
[2/2] arm64/mm: Avoid ID mapping of kpti flag if it is no longer needed
      https://git.kernel.org/arm64/c/27f2b9fcddc7

-- 
Catalin


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