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

maobibo
2020-09-07T13:11:01Z

On 09/07/2020 06:35 PM, Huang Pei wrote:
> 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* ?
>
macro pte_sw_mkyoung is added by me previously, and it is defined as empty excepts mips
system. If it is not used any more on mips sytem, I suggest that it should be removed here.

regards
bibo,mao