Re: [PATCH] MIPS: make userspace mapping young by default

Huang Pei
2020-09-07T10:36:50Z

On Mon, Sep 07, 2020 at 04:50:45PM +0800, maobibo wrote:
> Sorry for the late reply.
>
> Would you like to remove definition of macro pte_sw_mkyoung in header
> file include/linux/pgtable.h, since it is not used any more.
>
> The others look good to me.
>
> regards
> bibo,mao
>
> On 09/04/2020 04:49 PM, Huang Pei wrote:
> > This version removes pte_sw_mkyoung without polluting MM code and covers
> > both no-RIXI and RIXI MIPS CPUs and makes page fault delay of MIPS on par
> > with other architecture
> >
> > MIPS page fault path take 3 exceptions (1 TLB Miss + 2 TLB Invalid), but
> > the second TLB Invalid exception is just triggered by __update_tlb from
> > do_page_fault writing tlb without _PAGE_VALID set. By making userspace
> > mapping young by default, aka _PAGE_VALID and _PAGE_ACCESSED both set in
> > prot, it only take 1 TLB Miss + 1 TLB Invalid exceptions
> >
> > [1]: https://lkml.kernel.org/lkml/1591416169-26666-1-git-send-email
> > -maobibo@loongson.cn/
> >
> > Co-developed-by: Bibo Mao <maobibo@loonson.cn>
> > Co-developed-by: Huang Pei <huangpei@loongson.cn>
> > Signed-off-by: Huang Pei <huangpei@loongson.cn>
> > ---
> > arch/mips/include/asm/pgtable.h | 32 +++++++++++++++-----------------
> > arch/mips/mm/cache.c | 25 +++++++++++++------------
> > mm/memory.c | 3 ---
> > 3 files changed, 28 insertions(+), 32 deletions(-)
> >
> > diff --git a/arch/mips/include/asm/pgtable.h b/arch/mips/include/asm/pgtable.h
> > index dd7a0f552cac..aaafe3d6a0a1 100644
> > --- a/arch/mips/include/asm/pgtable.h
> > +++ b/arch/mips/include/asm/pgtable.h
> > @@ -25,22 +25,22 @@
> > struct mm_struct;
> > struct vm_area_struct;
> >
> > -#define PAGE_NONE __pgprot(_PAGE_PRESENT | _PAGE_NO_READ | \
> > - _page_cachable_default)
> > -#define PAGE_SHARED __pgprot(_PAGE_PRESENT | _PAGE_WRITE | \
> > - _page_cachable_default)
> > -#define PAGE_COPY __pgprot(_PAGE_PRESENT | _PAGE_NO_EXEC | \
> > - _page_cachable_default)
> > -#define PAGE_READONLY __pgprot(_PAGE_PRESENT | \
> > - _page_cachable_default)
> > -#define PAGE_KERNEL __pgprot(_PAGE_PRESENT | __READABLE | __WRITEABLE | \
> > - _PAGE_GLOBAL | _page_cachable_default)
> > -#define PAGE_KERNEL_NC __pgprot(_PAGE_PRESENT | __READABLE | __WRITEABLE | \
> > - _PAGE_GLOBAL | _CACHE_CACHABLE_NONCOHERENT)
> > -#define PAGE_USERIO __pgprot(_PAGE_PRESENT | _PAGE_WRITE | \
> > - _page_cachable_default)
> > +#define PAGE_NONE __pgprot(_PAGE_PRESENT | _PAGE_NO_READ | \
> > + _page_cachable_default)
> > +#define PAGE_SHARED __pgprot(_PAGE_PRESENT | _PAGE_WRITE | \
> > + __READABLE | _page_cachable_default)
> > +#define PAGE_COPY __pgprot(_PAGE_PRESENT | _PAGE_NO_EXEC | \
> > + __READABLE | _page_cachable_default)
> > +#define PAGE_READONLY __pgprot(_PAGE_PRESENT | __READABLE | \
> > + _page_cachable_default)
> > +#define PAGE_KERNEL __pgprot(_PAGE_PRESENT | __READABLE | __WRITEABLE | \
> > + _PAGE_GLOBAL | _page_cachable_default)
> > +#define PAGE_KERNEL_NC __pgprot(_PAGE_PRESENT | __READABLE | __WRITEABLE | \
> > + _PAGE_GLOBAL | _CACHE_CACHABLE_NONCOHERENT)
> > +#define PAGE_USERIO __pgprot(_PAGE_PRESENT | _PAGE_WRITE | \
> > + _page_cachable_default)
> > #define PAGE_KERNEL_UNCACHED __pgprot(_PAGE_PRESENT | __READABLE | \
> > - __WRITEABLE | _PAGE_GLOBAL | _CACHE_UNCACHED)
> > + __WRITEABLE | _PAGE_GLOBAL | _CACHE_UNCACHED)
> >
> > /*
> > * If _PAGE_NO_EXEC is not defined, we can't do page protection for
> > @@ -414,8 +414,6 @@ static inline pte_t pte_mkyoung(pte_t pte)
> > return pte;
> > }
> >
> > -#define pte_sw_mkyoung pte_mkyoung
> > -
> > #ifdef CONFIG_MIPS_HUGE_TLB_SUPPORT
> > static inline int pte_huge(pte_t pte) { return pte_val(pte) & _PAGE_HUGE; }
> >
> > diff --git a/arch/mips/mm/cache.c b/arch/mips/mm/cache.c
> > index 3e81ba000096..ed75f2871aad 100644
> > --- a/arch/mips/mm/cache.c
> > +++ b/arch/mips/mm/cache.c
> > @@ -159,22 +159,23 @@ static inline void setup_protection_map(void)
> > {
> > if (cpu_has_rixi) {
> > protection_map[0] = __pgprot(_page_cachable_default | _PAGE_PRESENT | _PAGE_NO_EXEC | _PAGE_NO_READ);
> > - protection_map[1] = __pgprot(_page_cachable_default | _PAGE_PRESENT | _PAGE_NO_EXEC);
> > + protection_map[1] = __pgprot(_page_cachable_default | _PAGE_PRESENT | _PAGE_NO_EXEC | __READABLE);
> > protection_map[2] = __pgprot(_page_cachable_default | _PAGE_PRESENT | _PAGE_NO_EXEC | _PAGE_NO_READ);
> > - protection_map[3] = __pgprot(_page_cachable_default | _PAGE_PRESENT | _PAGE_NO_EXEC);
> > - protection_map[4] = __pgprot(_page_cachable_default | _PAGE_PRESENT);
> > - protection_map[5] = __pgprot(_page_cachable_default | _PAGE_PRESENT);
> > - protection_map[6] = __pgprot(_page_cachable_default | _PAGE_PRESENT);
> > - protection_map[7] = __pgprot(_page_cachable_default | _PAGE_PRESENT);
> > + protection_map[3] = __pgprot(_page_cachable_default | _PAGE_PRESENT | _PAGE_NO_EXEC | __READABLE);
> > + protection_map[4] = __pgprot(_page_cachable_default | _PAGE_PRESENT | __READABLE);
> > + protection_map[5] = __pgprot(_page_cachable_default | _PAGE_PRESENT | __READABLE);
> > + protection_map[6] = __pgprot(_page_cachable_default | _PAGE_PRESENT | __READABLE);
> > + protection_map[7] = __pgprot(_page_cachable_default | _PAGE_PRESENT | __READABLE);
> >
> > protection_map[8] = __pgprot(_page_cachable_default | _PAGE_PRESENT | _PAGE_NO_EXEC | _PAGE_NO_READ);
> > - protection_map[9] = __pgprot(_page_cachable_default | _PAGE_PRESENT | _PAGE_NO_EXEC);
> > + protection_map[9] = __pgprot(_page_cachable_default | _PAGE_PRESENT | _PAGE_NO_EXEC | __READABLE);
> > protection_map[10] = __pgprot(_page_cachable_default | _PAGE_PRESENT | _PAGE_NO_EXEC | _PAGE_WRITE | _PAGE_NO_READ);
> > - protection_map[11] = __pgprot(_page_cachable_default | _PAGE_PRESENT | _PAGE_NO_EXEC | _PAGE_WRITE);
> > - protection_map[12] = __pgprot(_page_cachable_default | _PAGE_PRESENT);
> > - protection_map[13] = __pgprot(_page_cachable_default | _PAGE_PRESENT);
> > - protection_map[14] = __pgprot(_page_cachable_default | _PAGE_PRESENT | _PAGE_WRITE);
> > - protection_map[15] = __pgprot(_page_cachable_default | _PAGE_PRESENT | _PAGE_WRITE);
> > + protection_map[11] = __pgprot(_page_cachable_default | _PAGE_PRESENT | _PAGE_NO_EXEC | _PAGE_WRITE | __READABLE);
> > + protection_map[12] = __pgprot(_page_cachable_default | _PAGE_PRESENT | __READABLE);
> > + protection_map[13] = __pgprot(_page_cachable_default | _PAGE_PRESENT | __READABLE);
> > + protection_map[14] = __pgprot(_page_cachable_default | _PAGE_PRESENT | _PAGE_NO_EXEC | __READABLE);
> > + protection_map[15] = __pgprot(_page_cachable_default | _PAGE_PRESENT | _PAGE_NO_EXEC | __READABLE);
> > +
> >
> > } else {
> > protection_map[0] = PAGE_NONE;
> > diff --git a/mm/memory.c b/mm/memory.c
> > index 602f4283122f..5100ab5bcf77 100644
> > --- a/mm/memory.c
> > +++ b/mm/memory.c
> > @@ -2705,7 +2705,6 @@ static vm_fault_t wp_page_copy(struct vm_fault *vmf)
> > }
> > flush_cache_page(vma, vmf->address, pte_pfn(vmf->orig_pte));
> > entry = mk_pte(new_page, vma->vm_page_prot);
> > - entry = pte_sw_mkyoung(entry);
> > entry = maybe_mkwrite(pte_mkdirty(entry), vma);
> > /*
> > * Clear the pte entry and flush it first, before updating the
> > @@ -3386,7 +3385,6 @@ static vm_fault_t do_anonymous_page(struct vm_fault *vmf)
> > __SetPageUptodate(page);
> >
> > entry = mk_pte(page, vma->vm_page_prot);
> > - entry = pte_sw_mkyoung(entry);
> > if (vma->vm_flags & VM_WRITE)
> > entry = pte_mkwrite(pte_mkdirty(entry));
> >
> > @@ -3661,7 +3659,6 @@ vm_fault_t alloc_set_pte(struct vm_fault *vmf, struct page *page)
> >
> > flush_icache_page(vma, page);
> > entry = mk_pte(page, vma->vm_page_prot);
> > - entry = pte_sw_mkyoung(entry);
> > if (write)
> > entry = maybe_mkwrite(pte_mkdirty(entry), vma);
> > /* copy-on-write page */
> >

I search for pte_sw_mkyoung/pte_{clear,mk,}_savewrite, none of which is
used, do I really need to remove pte_sw_mkyoung in this patch just for
*not used* ?