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Message-ID: <1487044759.21048.24.camel@neuling.org>
Date: Tue, 14 Feb 2017 14:59:19 +1100
From: Michael Neuling <mikey@...ling.org>
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
Subject: Re: [PATCH 2/2] powerpc/mm/autonuma: Switch ppc64 to its own
implementeation of saved write
On Thu, 2017-02-09 at 08:30 +0530, Aneesh Kumar K.V wrote:
> With this our protnone becomes a present pte with READ/WRITE/EXEC bit cleared.
> By default we also set _PAGE_PRIVILEGED on such pte. This is now used to help
> us identify a protnone pte that as saved write bit. For such pte, we will
> clear
> the _PAGE_PRIVILEGED bit. The pte still remain non-accessible from both user
> and kernel.
>
> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@...ux.vnet.ibm.com>
FWIW I've tested this, so:
Acked-By: Michael Neuling <mikey@...ling.org>
> ---
> arch/powerpc/include/asm/book3s/64/mmu-hash.h | 3 +++
> arch/powerpc/include/asm/book3s/64/pgtable.h | 32 +++++++++++++++++++++++++-
> -
> 2 files changed, 33 insertions(+), 2 deletions(-)
>
> 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
> /*
> * This is necessary to get the definition of PGTABLE_RANGE which we
> * need for various slices related matters. Note that this isn't the
> diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h
> b/arch/powerpc/include/asm/book3s/64/pgtable.h
> index e91ada786d48..efff910a84b1 100644
> --- a/arch/powerpc/include/asm/book3s/64/pgtable.h
> +++ b/arch/powerpc/include/asm/book3s/64/pgtable.h
> @@ -443,8 +443,8 @@ static inline pte_t pte_clear_soft_dirty(pte_t pte)
> */
> static inline int pte_protnone(pte_t pte)
> {
> - return (pte_raw(pte) & cpu_to_be64(_PAGE_PRESENT | _PAGE_PRIVILEGED))
> ==
> - cpu_to_be64(_PAGE_PRESENT | _PAGE_PRIVILEGED);
> + return (pte_raw(pte) & cpu_to_be64(_PAGE_PRESENT | _PAGE_RWX)) ==
> + cpu_to_be64(_PAGE_PRESENT);
> }
> #endif /* CONFIG_NUMA_BALANCING */
>
> @@ -514,6 +514,32 @@ 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);
> +}
> +
> +#define pte_savedwrite pte_savedwrite
> +static inline bool pte_savedwrite(pte_t pte)
> +{
> + /*
> + * Saved write ptes are prot none ptes that doesn't have
> + * privileged bit sit. We mark prot none as one which has
> + * present and pviliged bit set and RWX cleared. To mark
> + * protnone which used to have _PAGE_WRITE set we clear
> + * the privileged bit.
> + */
> + return !(pte_raw(pte) & cpu_to_be64(_PAGE_RWX | _PAGE_PRIVILEGED));
> +}
> +
> static inline pte_t pte_mkdevmap(pte_t pte)
> {
> return __pte(pte_val(pte) | _PAGE_SPECIAL|_PAGE_DEVMAP);
> @@ -885,6 +911,7 @@ static inline pte_t *pmdp_ptep(pmd_t *pmd)
> #define pmd_mkclean(pmd) pte_pmd(pte_mkclean(pmd_pte(pmd)))
> #define pmd_mkyoung(pmd) pte_pmd(pte_mkyoung(pmd_pte(pmd)))
> #define pmd_mkwrite(pmd) pte_pmd(pte_mkwrite(pmd_pte(pmd)))
> +#define pmd_mk_savedwrite(pmd) pte_pmd(pte_mk_savedwrite(pmd_pte(pmd))
> )
>
> #ifdef CONFIG_HAVE_ARCH_SOFT_DIRTY
> #define pmd_soft_dirty(pmd) pte_soft_dirty(pmd_pte(pmd))
> @@ -901,6 +928,7 @@ static inline int pmd_protnone(pmd_t pmd)
>
> #define __HAVE_ARCH_PMD_WRITE
> #define pmd_write(pmd) pte_write(pmd_pte(pmd))
> +#define pmd_savedwrite(pmd) pte_savedwrite(pmd_pte(pmd))
>
> #ifdef CONFIG_TRANSPARENT_HUGEPAGE
> extern pmd_t pfn_pmd(unsigned long pfn, pgprot_t pgprot);
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