Messages in this thread | | | Date | Fri, 7 Jul 2023 14:09:07 +0200 | From | David Hildenbrand <> | Subject | Re: [RFC 1/4] arm64/mm: Add SW and HW dirty state helpers |
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On 07.07.23 07:33, Anshuman Khandual wrote: > This factors out low level SW and HW state changes i.e make and clear into > separate helpers making them explicit improving readability. This also adds > pte_rdonly() helper as well. No functional change is intended. > > Cc: Catalin Marinas <catalin.marinas@arm.com> > Cc: Will Deacon <will@kernel.org> > Cc: linux-arm-kernel@lists.infradead.org > Cc: linux-kernel@vger.kernel.org > Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com> > --- > arch/arm64/include/asm/pgtable.h | 52 ++++++++++++++++++++++++++------ > 1 file changed, 42 insertions(+), 10 deletions(-) > > diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h > index 0bd18de9fd97..fb03be697819 100644 > --- a/arch/arm64/include/asm/pgtable.h > +++ b/arch/arm64/include/asm/pgtable.h > @@ -103,6 +103,7 @@ static inline pteval_t __phys_to_pte_val(phys_addr_t phys) > #define pte_young(pte) (!!(pte_val(pte) & PTE_AF)) > #define pte_special(pte) (!!(pte_val(pte) & PTE_SPECIAL)) > #define pte_write(pte) (!!(pte_val(pte) & PTE_WRITE)) > +#define pte_rdonly(pte) (!!(pte_val(pte) & PTE_RDONLY)) > #define pte_user(pte) (!!(pte_val(pte) & PTE_USER)) > #define pte_user_exec(pte) (!(pte_val(pte) & PTE_UXN)) > #define pte_cont(pte) (!!(pte_val(pte) & PTE_CONT)) > @@ -120,7 +121,7 @@ static inline pteval_t __phys_to_pte_val(phys_addr_t phys) > (__boundary - 1 < (end) - 1) ? __boundary : (end); \ > }) > > -#define pte_hw_dirty(pte) (pte_write(pte) && !(pte_val(pte) & PTE_RDONLY)) > +#define pte_hw_dirty(pte) (pte_write(pte) && !pte_rdonly(pte)) > #define pte_sw_dirty(pte) (!!(pte_val(pte) & PTE_DIRTY)) > #define pte_dirty(pte) (pte_sw_dirty(pte) || pte_hw_dirty(pte)) > > @@ -174,6 +175,39 @@ static inline pmd_t clear_pmd_bit(pmd_t pmd, pgprot_t prot) > return pmd; > } > > +static inline pte_t pte_hw_mkdirty(pte_t pte)
I'd have called this "pte_mkhw_dirty", similar to "pte_mksoft_dirty".
> +{ > + if (pte_write(pte)) > + pte = clear_pte_bit(pte, __pgprot(PTE_RDONLY)); > + > + return pte; > +} > + > +static inline pte_t pte_sw_mkdirty(pte_t pte)
pte_mksw_dirty
> +{ > + return set_pte_bit(pte, __pgprot(PTE_DIRTY)); > +} > + > +static inline __always_unused pte_t pte_hw_clr_dirty(pte_t pte)
pte_clear_hw_dirty (again, similar to pte_clear_soft_dirty )
> +{ > + return set_pte_bit(pte, __pgprot(PTE_RDONLY)); > +} > + > +static inline pte_t pte_sw_clr_dirty(pte_t pte)
pte_clear_sw_dirty
> +{ > + pte = clear_pte_bit(pte, __pgprot(PTE_DIRTY)); > + > + /* > + * Clearing the software dirty state requires clearing > + * the PTE_DIRTY bit along with setting the PTE_RDONLY > + * ensuring a page fault on subsequent write access. > + * > + * NOTE: Setting the PTE_RDONLY (as a coincident) also > + * implies clearing the HW dirty state. > + */ > + return set_pte_bit(pte, __pgprot(PTE_RDONLY)); > +} > + > static inline pmd_t set_pmd_bit(pmd_t pmd, pgprot_t prot) > { > pmd_val(pmd) |= pgprot_val(prot); > @@ -189,19 +223,17 @@ static inline pte_t pte_mkwrite(pte_t pte) > > static inline pte_t pte_mkclean(pte_t pte) > { > - pte = clear_pte_bit(pte, __pgprot(PTE_DIRTY)); > - pte = set_pte_bit(pte, __pgprot(PTE_RDONLY)); > - > - return pte; > + /* > + * Subsequent call to pte_hw_clr_dirty() is not required > + * because pte_sw_clr_dirty() in turn does that as well. > + */ > + return pte_sw_clr_dirty(pte);
Hm, I'm not sure if that simplifies things.
You call pte_sw_clr_dirty() and suddenly your hw dirty bit is clear?
In that case I think the current implementation is clearer: it doesn't provide primitives that don't make any sense.
> } > > static inline pte_t pte_mkdirty(pte_t pte) > { > - pte = set_pte_bit(pte, __pgprot(PTE_DIRTY)); > - > - if (pte_write(pte)) > - pte = clear_pte_bit(pte, __pgprot(PTE_RDONLY)); > - > + pte = pte_sw_mkdirty(pte); > + pte = pte_hw_mkdirty(pte);
That looks weird. Especially, pte_hw_mkdirty() only does something if pte_write().
Shouldn't pte_hw_mkdirty() bail out if it cannot do anything reasonable (IOW, !writable)?
> return pte; > } >
-- Cheers,
David / dhildenb
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