linux-kernel - Re: [PATCH] x86/mm: fix pg_level_to

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Message-ID: <ZSpVtZhks7Wm5Upc@gmail.com>
Date:   Sat, 14 Oct 2023 10:47:49 +0200
From:   Ingo Molnar <mingo@...nel.org>
To:     Ashish Kalra <Ashish.Kalra@....com>
Cc:     dave.hansen@...ux.intel.com, luto@...nel.org, tglx@...utronix.de,
        mingo@...hat.com, bp@...en8.de, x86@...nel.org, hpa@...or.com,
        thomas.lendacky@....com, linux-kernel@...r.kernel.org,
        peterz@...radead.org
Subject: Re: [PATCH] x86/mm: fix pg_level_to_pfn for 5-level paging mode.


* Ashish Kalra <Ashish.Kalra@....com> wrote:

> From: Ashish Kalra <ashish.kalra@....com>
> 
> Add support for 5-level paging in pg_level_to_pfn().
> 
> Signed-off-by: Ashish Kalra <ashish.kalra@....com>
> ---
>  arch/x86/mm/mem_encrypt_amd.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/arch/x86/mm/mem_encrypt_amd.c b/arch/x86/mm/mem_encrypt_amd.c
> index 6faea41e99b6..45914568596a 100644
> --- a/arch/x86/mm/mem_encrypt_amd.c
> +++ b/arch/x86/mm/mem_encrypt_amd.c
> @@ -267,6 +267,10 @@ static unsigned long pg_level_to_pfn(int level, pte_t *kpte, pgprot_t *ret_prot)
>  		pfn = pud_pfn(*(pud_t *)kpte);
>  		prot = pud_pgprot(*(pud_t *)kpte);
>  		break;
> +	case PG_LEVEL_512G:
> +		pfn = p4d_pfn(*(p4d_t *)kpte);
> +		prot = p4d_pgprot(*(p4d_t *)kpte);
> +		break;

Mind explaining what happens if we don't have this fix, how you found it, 
which users are expected to be affected by it, whether that's the full 
known extent of 5-level paging support deficiencies in mem_encrypt_amd.c, 
etc?

In addition to such patches being much easier on the eyes, it also helps 
maintainers prioritize patches.

Thanks,

	Ingo