Messages in this thread | | | From | Nico Pache <> | Date | Tue, 4 Jul 2023 05:58:13 -0400 | Subject | Re: [RFC] arm64: properly define SOFT_DIRTY for arm64 |
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Whoops I pulled but never actually rebased... commit e1fd09e3d1dd ("mm: x86, arm64: add arch_has_hw_pte_young()") changed arch_faults_on_old_pte() into !arch_has_hw_pte_young(). Following up with a V2 shortly.
-- Nico
On Mon, Jul 3, 2023 at 10:06 AM Nico Pache <npache@redhat.com> wrote: > > ARM64 has a soft-dirty bit (software dirty) but never properly defines > CONFIG_ARCH_HAS_SOFT_DIRTY or its necessary functions. This patch > introduces the ability to set/clear the soft dirty bit in a similar > manner as the other arches that utilize it. > > However, we must be careful... there are cases where the DBM bit is not > available and the software dirty bit plays a essential role in determining > whether or not a page is dirty. In these cases we must not allow the > user to clear the software dirty bit. We can test for these cases by > utilizing the arch_faults_on_old_pte() function which test the availability > of DBM. > > Cc: Andrew Morton <akpm@linux-foundation.org> > Cc: Anshuman Khandual <anshuman.khandual@arm.com> > Cc: Catalin Marinas <catalin.marinas@arm.com> > Cc: David Hildenbrand <david@redhat.com> > Cc: Gerald Schaefer <gerald.schaefer@linux.ibm.com> > Cc: Liu Shixin <liushixin2@huawei.com> > Cc: Will Deacon <will@kernel.org> > Cc: Yu Zhao <yuzhao@google.com> > Signed-off-by: Nico Pache <npache@redhat.com> > --- > arch/arm64/Kconfig | 1 + > arch/arm64/include/asm/pgtable.h | 77 +++++++++++++++++++++++++++++++- > 2 files changed, 76 insertions(+), 2 deletions(-) > > diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig > index 891ab530a665..4de491627f49 100644 > --- a/arch/arm64/Kconfig > +++ b/arch/arm64/Kconfig > @@ -173,6 +173,7 @@ config ARM64 > select HAVE_ARCH_PREL32_RELOCATIONS > select HAVE_ARCH_RANDOMIZE_KSTACK_OFFSET > select HAVE_ARCH_SECCOMP_FILTER > + select HAVE_ARCH_SOFT_DIRTY > select HAVE_ARCH_STACKLEAK > select HAVE_ARCH_THREAD_STRUCT_WHITELIST > select HAVE_ARCH_TRACEHOOK > diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h > index 0bd18de9fd97..a0a15ffa2417 100644 > --- a/arch/arm64/include/asm/pgtable.h > +++ b/arch/arm64/include/asm/pgtable.h > @@ -121,8 +121,9 @@ static inline pteval_t __phys_to_pte_val(phys_addr_t phys) > }) > > #define pte_hw_dirty(pte) (pte_write(pte) && !(pte_val(pte) & PTE_RDONLY)) > -#define pte_sw_dirty(pte) (!!(pte_val(pte) & PTE_DIRTY)) > -#define pte_dirty(pte) (pte_sw_dirty(pte) || pte_hw_dirty(pte)) > +#define pte_soft_dirty(pte) (!!(pte_val(pte) & PTE_DIRTY)) > +#define pte_dirty(pte) (pte_soft_dirty(pte) || pte_hw_dirty(pte)) > +#define pte_swp_soft_dirty(pte) pte_soft_dirty(pte) > > #define pte_valid(pte) (!!(pte_val(pte) & PTE_VALID)) > /* > @@ -1096,6 +1097,78 @@ static inline bool pud_sect_supported(void) > return PAGE_SIZE == SZ_4K; > } > > +#ifdef CONFIG_ARM64_HW_AFDBM > +/* > + * if we have the DBM bit we can utilize the software dirty bit as > + * a mechanism to introduce the soft_dirty functionality; however, without > + * it this bit is crucial to determining if a entry is dirty and we cannot > + * clear it via software. DBM can also be disabled or broken on some early > + * armv8 devices, so check its availability before modifying it. > + */ > +static inline pte_t pte_clear_soft_dirty(pte_t pte) > +{ > + if (arch_faults_on_old_pte()) > + return pte; > + > + return clear_pte_bit(pte, __pgprot(PTE_DIRTY)); > +} > + > +static inline pte_t pte_mksoft_dirty(pte_t pte) > +{ > + if (arch_faults_on_old_pte()) > + return pte; > + > + return set_pte_bit(pte, __pgprot(PTE_DIRTY)); > +} > + > +static inline pte_t pte_swp_clear_soft_dirty(pte_t pte) > +{ > + if (arch_faults_on_old_pte()) > + return pte; > + > + return clear_pte_bit(pte, __pgprot(PTE_DIRTY)); > +} > + > +static inline pte_t pte_swp_mksoft_dirty(pte_t pte) > +{ > + if (arch_faults_on_old_pte()) > + return pte; > + > + return set_pte_bit(pte, __pgprot(PTE_DIRTY)); > +} > + > +static inline int pmd_soft_dirty(pmd_t pmd) > +{ > + return pte_soft_dirty(pmd_pte(pmd)); > +} > + > +static inline pmd_t pmd_clear_soft_dirty(pmd_t pmd) > +{ > + return pte_pmd(pte_clear_soft_dirty(pmd_pte(pmd))); > +} > + > +static inline pmd_t pmd_mksoft_dirty(pmd_t pmd) > +{ > + return pte_pmd(pte_mksoft_dirty(pmd_pte(pmd))); > +} > + > +#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION > +static inline int pmd_swp_soft_dirty(pmd_t pmd) > +{ > + return pmd_soft_dirty(pmd); > +} > + > +static inline pmd_t pmd_swp_clear_soft_dirty(pmd_t pmd) > +{ > + return pmd_clear_soft_dirty(pmd); > +} > + > +static inline pmd_t pmd_swp_mksoft_dirty(pmd_t pmd) > +{ > + return pmd_mksoft_dirty(pmd); > +} > +#endif /* CONFIG_ARCH_ENABLE_THP_MIGRATION */ > +#endif /* CONFIG_ARM64_HW_AFDBM */ > > #define __HAVE_ARCH_PTEP_MODIFY_PROT_TRANSACTION > #define ptep_modify_prot_start ptep_modify_prot_start > -- > 2.41.0 >
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