linux-kernel - Re: [PATCH v17 06/23] powerpc: mm: Add p?d

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Message-ID: <877e2smt6r.fsf@mpe.ellerman.id.au>
Date:   Thu, 19 Dec 2019 22:49:16 +1100
From:   Michael Ellerman <mpe@...erman.id.au>
To:     Steven Price <steven.price@....com>,
        Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org
Cc:     Steven Price <steven.price@....com>,
        Andy Lutomirski <luto@...nel.org>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        Arnd Bergmann <arnd@...db.de>, Borislav Petkov <bp@...en8.de>,
        Catalin Marinas <catalin.marinas@....com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Ingo Molnar <mingo@...hat.com>,
        James Morse <james.morse@....com>,
        Jérôme Glisse <jglisse@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Will Deacon <will@...nel.org>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Mark Rutland <Mark.Rutland@....com>,
        "Liang\, Kan" <kan.liang@...ux.intel.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        linuxppc-dev@...ts.ozlabs.org, kvm-ppc@...r.kernel.org
Subject: Re: [PATCH v17 06/23] powerpc: mm: Add p?d_leaf() definitions

Steven Price <steven.price@....com> writes:
> walk_page_range() is going to be allowed to walk page tables other than
> those of user space. For this it needs to know when it has reached a
> 'leaf' entry in the page tables. This information is provided by the
> p?d_leaf() functions/macros.
>
> For powerpc p?d_is_leaf() functions already exist. Export them using the
> new p?d_leaf() name.
>
> CC: Benjamin Herrenschmidt <benh@...nel.crashing.org>
> CC: Paul Mackerras <paulus@...ba.org>
> CC: Michael Ellerman <mpe@...erman.id.au>
> CC: linuxppc-dev@...ts.ozlabs.org
> CC: kvm-ppc@...r.kernel.org
> Signed-off-by: Steven Price <steven.price@....com>
> ---
>  arch/powerpc/include/asm/book3s/64/pgtable.h | 3 +++
>  1 file changed, 3 insertions(+)

We have fallback versions of our pmd_is_leaf() etc. in
arch/powerpc/include/asm/pgtable.h, eg:

#ifndef pmd_is_leaf
#define pmd_is_leaf pmd_is_leaf
static inline bool pmd_is_leaf(pmd_t pmd)
{
	return false;
}
#endif

Because we support several different MMUs and most of them don't need to
do anything.

So we could put the compatibility #defines to your names along with the
fallback versions in asm/pgtable.h, rather than in
asm/book3s/64/pgtable.h

But I see you also have fallbacks for your versions, so it probably
doesn't matter either way.

So I'm OK with this version, unless you think there's a compelling
reason to do the compatibility #defines in our asm/pgtable.h

Acked-by: Michael Ellerman <mpe@...erman.id.au>

cheers


> diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h b/arch/powerpc/include/asm/book3s/64/pgtable.h
> index b01624e5c467..201a69e6a355 100644
> --- a/arch/powerpc/include/asm/book3s/64/pgtable.h
> +++ b/arch/powerpc/include/asm/book3s/64/pgtable.h
> @@ -1355,18 +1355,21 @@ static inline bool is_pte_rw_upgrade(unsigned long old_val, unsigned long new_va
>   * Like pmd_huge() and pmd_large(), but works regardless of config options
>   */
>  #define pmd_is_leaf pmd_is_leaf
> +#define pmd_leaf pmd_is_leaf
>  static inline bool pmd_is_leaf(pmd_t pmd)
>  {
>  	return !!(pmd_raw(pmd) & cpu_to_be64(_PAGE_PTE));
>  }
>  
>  #define pud_is_leaf pud_is_leaf
> +#define pud_leaf pud_is_leaf
>  static inline bool pud_is_leaf(pud_t pud)
>  {
>  	return !!(pud_raw(pud) & cpu_to_be64(_PAGE_PTE));
>  }
>  
>  #define pgd_is_leaf pgd_is_leaf
> +#define pgd_leaf pgd_is_leaf
>  static inline bool pgd_is_leaf(pgd_t pgd)
>  {
>  	return !!(pgd_raw(pgd) & cpu_to_be64(_PAGE_PTE));
> -- 
> 2.20.1