linux-kernel - Re: [PATCH v1 03/16] arm64: hugetlb: Fix flush_hugetlb_tlb

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Message-ID: <e2809c59-6453-4a90-88ad-0b22e82f869f@arm.com>
Date: Thu, 6 Feb 2025 12:16:02 +0530
From: Anshuman Khandual <anshuman.khandual@....com>
To: Ryan Roberts <ryan.roberts@....com>,
 Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>,
 Muchun Song <muchun.song@...ux.dev>,
 Pasha Tatashin <pasha.tatashin@...een.com>,
 Andrew Morton <akpm@...ux-foundation.org>,
 Uladzislau Rezki <urezki@...il.com>, Christoph Hellwig <hch@...radead.org>,
 Mark Rutland <mark.rutland@....com>, Ard Biesheuvel <ardb@...nel.org>,
 Dev Jain <dev.jain@....com>, Alexandre Ghiti <alexghiti@...osinc.com>,
 Steve Capper <steve.capper@...aro.org>, Kevin Brodsky <kevin.brodsky@....com>
Cc: linux-arm-kernel@...ts.infradead.org, linux-mm@...ck.org,
 linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH v1 03/16] arm64: hugetlb: Fix flush_hugetlb_tlb_range()
 invalidation level



On 2/5/25 20:39, Ryan Roberts wrote:
> commit c910f2b65518 ("arm64/mm: Update tlb invalidation routines for
> FEAT_LPA2") changed the "invalidation level unknown" hint from 0 to
> TLBI_TTL_UNKNOWN (INT_MAX). But the fallback "unknown level" path in
> flush_hugetlb_tlb_range() was not updated. So as it stands, when trying
> to invalidate CONT_PMD_SIZE or CONT_PTE_SIZE hugetlb mappings, we will
> spuriously try to invalidate at level 0 on LPA2-enabled systems.
> 
> Fix this so that the fallback passes TLBI_TTL_UNKNOWN, and while we are
> at it, explicitly use the correct stride and level for CONT_PMD_SIZE and
> CONT_PTE_SIZE, which should provide a minor optimization.
> 
> Cc: <stable@...r.kernel.org>
> Fixes: c910f2b65518 ("arm64/mm: Update tlb invalidation routines for FEAT_LPA2")
> Signed-off-by: Ryan Roberts <ryan.roberts@....com>
> ---
>  arch/arm64/include/asm/hugetlb.h | 20 ++++++++++++++------
>  1 file changed, 14 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/hugetlb.h b/arch/arm64/include/asm/hugetlb.h
> index 03db9cb21ace..8ab9542d2d22 100644
> --- a/arch/arm64/include/asm/hugetlb.h
> +++ b/arch/arm64/include/asm/hugetlb.h
> @@ -76,12 +76,20 @@ static inline void flush_hugetlb_tlb_range(struct vm_area_struct *vma,
>  {
>  	unsigned long stride = huge_page_size(hstate_vma(vma));
>  
> -	if (stride == PMD_SIZE)
> -		__flush_tlb_range(vma, start, end, stride, false, 2);
> -	else if (stride == PUD_SIZE)
> -		__flush_tlb_range(vma, start, end, stride, false, 1);
> -	else
> -		__flush_tlb_range(vma, start, end, PAGE_SIZE, false, 0);
> +	switch (stride) {
> +	case PUD_SIZE:
> +		__flush_tlb_range(vma, start, end, PUD_SIZE, false, 1);
> +		break;

Just wondering - should not !__PAGETABLE_PMD_FOLDED and pud_sect_supported()
checks also be added here for this PUD_SIZE case ?

> +	case CONT_PMD_SIZE:
> +	case PMD_SIZE:
> +		__flush_tlb_range(vma, start, end, PMD_SIZE, false, 2);
> +		break;
> +	case CONT_PTE_SIZE:
> +		__flush_tlb_range(vma, start, end, PAGE_SIZE, false, 3);
> +		break;
> +	default:
> +		__flush_tlb_range(vma, start, end, PAGE_SIZE, false, TLBI_TTL_UNKNOWN);
> +	}
>  }
>  
>  #endif /* __ASM_HUGETLB_H */