linux-kernel - Re: [PATCH V2] arm64/hugetlb: Consistently use pud_sect

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <0ad8b31e-f1f1-426d-89e8-a21cf72814d1@arm.com>
Date: Tue, 18 Feb 2025 14:01:58 +0000
From: Ryan Roberts <ryan.roberts@....com>
To: Anshuman Khandual <anshuman.khandual@....com>,
 linux-arm-kernel@...ts.infradead.org
Cc: Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH V2] arm64/hugetlb: Consistently use pud_sect_supported()

On 18/02/2025 11:36, Anshuman Khandual wrote:
> Let's be consistent in using pud_sect_supported() for PUD_SIZE sized pages.
> Hence change hugetlb_mask_last_page() and arch_make_huge_pte() as required.
> 
> Cc: Catalin Marinas <catalin.marinas@....com>
> Cc: Will Deacon <will@...nel.org>
> Cc: linux-arm-kernel@...ts.infradead.org
> Cc: linux-kernel@...r.kernel.org
> Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>
> ---
> This patch applies on v6.14-rc3
> 
> Changes in V2:
> 
> - Added an warning when PUD_SIZE is requested but not supported per Ryan
> 
> Changes in V1:
> 
> https://lore.kernel.org/all/20250217065414.49489-1-anshuman.khandual@arm.com/
> 
>  arch/arm64/mm/hugetlbpage.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c
> index 98a2a0e64e25..1d89599a20d7 100644
> --- a/arch/arm64/mm/hugetlbpage.c
> +++ b/arch/arm64/mm/hugetlbpage.c
> @@ -342,7 +342,9 @@ unsigned long hugetlb_mask_last_page(struct hstate *h)
>  	switch (hp_size) {
>  #ifndef __PAGETABLE_PMD_FOLDED
>  	case PUD_SIZE:
> -		return PGDIR_SIZE - PUD_SIZE;
> +		if (pud_sect_supported())
> +			return PGDIR_SIZE - PUD_SIZE;
> +		break;
>  #endif
>  	case CONT_PMD_SIZE:
>  		return PUD_SIZE - CONT_PMD_SIZE;
> @@ -364,7 +366,10 @@ pte_t arch_make_huge_pte(pte_t entry, unsigned int shift, vm_flags_t flags)
>  	switch (pagesize) {
>  #ifndef __PAGETABLE_PMD_FOLDED
>  	case PUD_SIZE:
> -		entry = pud_pte(pud_mkhuge(pte_pud(entry)));
> +		if (pud_sect_supported())
> +			entry = pud_pte(pud_mkhuge(pte_pud(entry)));
> +		else
> +			pr_warn("%s: pud huge page not supported\n", __func__);
>  		break;
>  #endif
>  	case CONT_PMD_SIZE:

Personally, I think something like this is cleaner than having 2 warnings:

pte_t arch_make_huge_pte(pte_t entry, unsigned int shift, vm_flags_t flags)
{
	size_t pagesize = 1UL << shift;

	switch (pagesize) {
#ifndef __PAGETABLE_PMD_FOLDED
	case PUD_SIZE:
		if (pud_sect_supported())
			return pud_pte(pud_mkhuge(pte_pud(entry)));
		break;
#endif
	case CONT_PMD_SIZE:
		return pmd_pte(pmd_mkhuge(pmd_mkcont(pte_pmd(entry))));
	case PMD_SIZE:
		return pmd_pte(pmd_mkhuge(pte_pmd(entry)));
	case CONT_PTE_SIZE:
		return pte_mkcont(entry);
	}

	pr_warn("%s: unrecognized huge page size 0x%lx\n",
		__func__, pagesize);
	return entry;
}

Thanks,
Ryan