linux-kernel - Re: [PATCH] x86/memory: Drop pud

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Message-ID: <20200323013732.GC3039@MiWiFi-R3L-srv>
Date:   Mon, 23 Mar 2020 09:37:32 +0800
From:   Baoquan He <bhe@...hat.com>
To:     Anshuman Khandual <anshuman.khandual@....com>
Cc:     linux-mm@...ck.org, jhubbard@...dia.com,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        Dave Hansen <dave.hansen@...el.com>,
        "Kirill A . Shutemov" <kirill@...temov.name>,
        Dan Williams <dan.j.williams@...el.com>,
        Andrew Morton <akpm@...ux-foundation.org>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86/memory: Drop pud_mknotpresent()

On 03/23/20 at 06:35am, Anshuman Khandual wrote:
> There is an inconsistency between PMD and PUD based THP page table helpers
> like the following, as pud_present() does not test for _PAGE_PSE.
> 
> pmd_present(pmd_mknotpresent(pmd)) : True
> pud_present(pud_mknotpresent(pud)) : False
> 
> This drops pud_mknotpresent() as there are no current users. If/when needed
> back later, pud_present() will also have to fixed to accommodate _PAGE_PSE.
> 
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: Borislav Petkov <bp@...en8.de>
> Cc: "H. Peter Anvin" <hpa@...or.com>
> Cc: Dave Hansen <dave.hansen@...el.com>
> Cc: Kirill A. Shutemov <kirill@...temov.name>
> Cc: Dan Williams <dan.j.williams@...el.com>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: x86@...nel.org
> Cc: linux-mm@...ck.org
> Cc: linux-kernel@...r.kernel.org
> Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>
> ---
> This has been build and boot tested on x86.
> 
> Changes in V2:
> 
> - Dropped pud_mknotpresent() instead per Kirill
> 
> Changes in V1: (https://patchwork.kernel.org/patch/11444529/)
> 
>  arch/x86/include/asm/pgtable.h | 6 ------
>  1 file changed, 6 deletions(-)
> 
> diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h
> index 7e118660bbd9..d74dc560e3ab 100644
> --- a/arch/x86/include/asm/pgtable.h
> +++ b/arch/x86/include/asm/pgtable.h
> @@ -595,12 +595,6 @@ static inline pmd_t pmd_mknotpresent(pmd_t pmd)
>  		      __pgprot(pmd_flags(pmd) & ~(_PAGE_PRESENT|_PAGE_PROTNONE)));
>  }
>  
> -static inline pud_t pud_mknotpresent(pud_t pud)
> -{
> -	return pfn_pud(pud_pfn(pud),
> -	      __pgprot(pud_flags(pud) & ~(_PAGE_PRESENT|_PAGE_PROTNONE)));
> -}
> -
>  static inline u64 flip_protnone_guard(u64 oldval, u64 val, u64 mask);
>  
>  static inline pte_t pte_modify(pte_t pte, pgprot_t newprot)

Reviewed-by: Baoquan He <bhe@...hat.com>