linux-kernel - Re: [PATCH V2 2/2] powerpc/mm/autonuma: Switch ppc64 to its own implementeation of saved write

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Message-ID: <87y3x9kp8e.fsf@concordia.ellerman.id.au>
Date:   Tue, 14 Feb 2017 22:04:33 +1100
From:   Michael Ellerman <mpe@...erman.id.au>
To:     "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
        akpm@...ux-foundation.org, Rik van Riel <riel@...riel.com>,
        Mel Gorman <mgorman@...hsingularity.net>, paulus@...abs.org,
        benh@...nel.crashing.org
Cc:     linux-mm@...ck.org, linuxppc-dev@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org,
        "Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
Subject: Re: [PATCH V2 2/2] powerpc/mm/autonuma: Switch ppc64 to its own implementeation of saved write

"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com> writes:
> diff --git a/arch/powerpc/include/asm/book3s/64/mmu-hash.h b/arch/powerpc/include/asm/book3s/64/mmu-hash.h
> index 0735d5a8049f..8720a406bbbe 100644
> --- a/arch/powerpc/include/asm/book3s/64/mmu-hash.h
> +++ b/arch/powerpc/include/asm/book3s/64/mmu-hash.h
> @@ -16,6 +16,9 @@
>  #include <asm/page.h>
>  #include <asm/bug.h>
>  
> +#ifndef __ASSEMBLY__
> +#include <linux/mmdebug.h>
> +#endif

I assume that's for the VM_BUG_ON() you add below. But if so wouldn't
the #include be better placed in book3s/64/pgtable.h also?

> diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h b/arch/powerpc/include/asm/book3s/64/pgtable.h
> index fef738229a68..c684ef6cbd10 100644
> --- a/arch/powerpc/include/asm/book3s/64/pgtable.h
> +++ b/arch/powerpc/include/asm/book3s/64/pgtable.h
> @@ -512,6 +512,32 @@ static inline pte_t pte_mkhuge(pte_t pte)
>  	return pte;
>  }
>  
> +#define pte_mk_savedwrite pte_mk_savedwrite
> +static inline pte_t pte_mk_savedwrite(pte_t pte)
> +{
> +	/*
> +	 * Used by Autonuma subsystem to preserve the write bit
> +	 * while marking the pte PROT_NONE. Only allow this
> +	 * on PROT_NONE pte
> +	 */
> +	VM_BUG_ON((pte_raw(pte) & cpu_to_be64(_PAGE_PRESENT | _PAGE_RWX | _PAGE_PRIVILEGED)) !=
> +		  cpu_to_be64(_PAGE_PRESENT | _PAGE_PRIVILEGED));
> +	return __pte(pte_val(pte) & ~_PAGE_PRIVILEGED);
> +}
> +


cheers