From: bibo mao <[email protected]>
If there are two threads reading the same memory and tlb miss happens,
one thread fills pte entry, the other reads new pte value during page fault
handling. PTE value may be updated before page faul, so the process need
need update tlb still.
Also this patch define flush_tlb_fix_spurious_fault as empty, since it not
necessary to flush the page for all CPUs
Signed-off-by: Bibo Mao <[email protected]>
---
arch/mips/include/asm/pgtable.h | 20 ++++++++++++++++++++
1 file changed, 20 insertions(+)
diff --git a/arch/mips/include/asm/pgtable.h b/arch/mips/include/asm/pgtable.h
index aab0ec1..d0a4940 100644
--- a/arch/mips/include/asm/pgtable.h
+++ b/arch/mips/include/asm/pgtable.h
@@ -635,6 +635,26 @@ static inline pmd_t pmd_mknotpresent(pmd_t pmd)
return pmd;
}
+#define flush_tlb_fix_spurious_fault(vma, address) do { } while (0)
+
+#define __HAVE_ARCH_PTEP_SET_ACCESS_FLAGS
+int ptep_set_access_flags(struct vm_area_struct *vma,
+ unsigned long address, pte_t *ptep,
+ pte_t entry, int dirty)
+{
+ int changed = !pte_same(*ptep, entry);
+
+ if (changed)
+ set_pte_at(vma->vm_mm, address, ptep, entry);
+ else
+ /* update tlb with latest pte entry still, tlb entry is old
+ * since there is page fault
+ */
+ update_mmu_cache(vma, address, ptep);
+
+ return changed;
+}
+
/*
* The generic version pmdp_huge_get_and_clear uses a version of pmd_clear() with a
* different prototype.
--
1.8.3.1
On Thu, May 14, 2020 at 10:17:57AM +0800, Bibo Mao wrote:
> From: bibo mao <[email protected]>
>
> If there are two threads reading the same memory and tlb miss happens,
> one thread fills pte entry, the other reads new pte value during page fault
> handling. PTE value may be updated before page faul, so the process need
> need update tlb still.
>
> Also this patch define flush_tlb_fix_spurious_fault as empty, since it not
> necessary to flush the page for all CPUs
I'm not familiar enough with MIPS TLB workings, but it seems that adding
a MIPS version of ptep_set_access_flags() and relaxing
flush_tlb_fix_spurious_fault() are two separate patches.
> Signed-off-by: Bibo Mao <[email protected]>
> ---
> arch/mips/include/asm/pgtable.h | 20 ++++++++++++++++++++
> 1 file changed, 20 insertions(+)
>
> diff --git a/arch/mips/include/asm/pgtable.h b/arch/mips/include/asm/pgtable.h
> index aab0ec1..d0a4940 100644
> --- a/arch/mips/include/asm/pgtable.h
> +++ b/arch/mips/include/asm/pgtable.h
> @@ -635,6 +635,26 @@ static inline pmd_t pmd_mknotpresent(pmd_t pmd)
> return pmd;
> }
>
> +#define flush_tlb_fix_spurious_fault(vma, address) do { } while (0)
> +
> +#define __HAVE_ARCH_PTEP_SET_ACCESS_FLAGS
> +int ptep_set_access_flags(struct vm_area_struct *vma,
> + unsigned long address, pte_t *ptep,
> + pte_t entry, int dirty)
> +{
> + int changed = !pte_same(*ptep, entry);
> +
> + if (changed)
> + set_pte_at(vma->vm_mm, address, ptep, entry);
> + else
> + /* update tlb with latest pte entry still, tlb entry is old
> + * since there is page fault
> + */
> + update_mmu_cache(vma, address, ptep);
> +
> + return changed;
> +}
> +
> /*
> * The generic version pmdp_huge_get_and_clear uses a version of pmd_clear() with a
> * different prototype.
> --
> 1.8.3.1
>
--
Sincerely yours,
Mike.
On 14.05.2020 5:17, Bibo Mao wrote:
> From: bibo mao <[email protected]>
>
> If there are two threads reading the same memory and tlb miss happens,
> one thread fills pte entry, the other reads new pte value during page fault
> handling. PTE value may be updated before page faul, so the process need
Fault.
> need update tlb still.
>
> Also this patch define flush_tlb_fix_spurious_fault as empty, since it not
> necessary to flush the page for all CPUs
>
> Signed-off-by: Bibo Mao <[email protected]>
[...]
MBR, Sergei
On 14.05.2020 12:35, Sergei Shtylyov wrote:
>> From: bibo mao <[email protected]>
>>
>> If there are two threads reading the same memory and tlb miss happens,
>> one thread fills pte entry, the other reads new pte value during page fault
>> handling. PTE value may be updated before page faul, so the process need
>
> Fault.
And "needs".
>> need update tlb still.
Oh, and one "need" is enough. :-)
>> Also this patch define flush_tlb_fix_spurious_fault as empty, since it not
>> necessary to flush the page for all CPUs
>>
>> Signed-off-by: Bibo Mao <[email protected]>
> [...]
MBR, Sergei
On 05/14/2020 05:33 PM, Mike Rapoport wrote:
> On Thu, May 14, 2020 at 10:17:57AM +0800, Bibo Mao wrote:
>> From: bibo mao <[email protected]>
>>
>> If there are two threads reading the same memory and tlb miss happens,
>> one thread fills pte entry, the other reads new pte value during page fault
>> handling. PTE value may be updated before page faul, so the process need
>> need update tlb still.
>>
>> Also this patch define flush_tlb_fix_spurious_fault as empty, since it not
>> necessary to flush the page for all CPUs
>
> I'm not familiar enough with MIPS TLB workings, but it seems that adding
> a MIPS version of ptep_set_access_flags() and relaxing
> flush_tlb_fix_spurious_fault() are two separate patches.
Well, will split it into two patches.
regards
bibo, mao
>
>> Signed-off-by: Bibo Mao <[email protected]>
>> ---
>> arch/mips/include/asm/pgtable.h | 20 ++++++++++++++++++++
>> 1 file changed, 20 insertions(+)
>>
>> diff --git a/arch/mips/include/asm/pgtable.h b/arch/mips/include/asm/pgtable.h
>> index aab0ec1..d0a4940 100644
>> --- a/arch/mips/include/asm/pgtable.h
>> +++ b/arch/mips/include/asm/pgtable.h
>> @@ -635,6 +635,26 @@ static inline pmd_t pmd_mknotpresent(pmd_t pmd)
>> return pmd;
>> }
>>
>> +#define flush_tlb_fix_spurious_fault(vma, address) do { } while (0)
>> +
>> +#define __HAVE_ARCH_PTEP_SET_ACCESS_FLAGS
>> +int ptep_set_access_flags(struct vm_area_struct *vma,
>> + unsigned long address, pte_t *ptep,
>> + pte_t entry, int dirty)
>> +{
>> + int changed = !pte_same(*ptep, entry);
>> +
>> + if (changed)
>> + set_pte_at(vma->vm_mm, address, ptep, entry);
>> + else
>> + /* update tlb with latest pte entry still, tlb entry is old
>> + * since there is page fault
>> + */
>> + update_mmu_cache(vma, address, ptep);
>> +
>> + return changed;
>> +}
>> +
>> /*
>> * The generic version pmdp_huge_get_and_clear uses a version of pmd_clear() with a
>> * different prototype.
>> --
>> 1.8.3.1
>>
>
On 05/14/2020 05:37 PM, Sergei Shtylyov wrote:
> On 14.05.2020 12:35, Sergei Shtylyov wrote:
>
>>> From: bibo mao <[email protected]>
>>>
>>> If there are two threads reading the same memory and tlb miss happens,
>>> one thread fills pte entry, the other reads new pte value during page fault
>>> handling. PTE value may be updated before page faul, so the process need
>>
>> Fault.
>
> And "needs".
>
>>> need update tlb still.
>
> Oh, and one "need" is enough. :-)
Thank for reviewing my patch, will fix this typo issue in next version.
Best Regards
bibo, mao
>
>>> Also this patch define flush_tlb_fix_spurious_fault as empty, since it not
>>> necessary to flush the page for all CPUs
>>>
>>> Signed-off-by: Bibo Mao <[email protected]>
>> [...]
>
> MBR, Sergei
On Thu, 14 May 2020, Sergei Shtylyov wrote:
> >> If there are two threads reading the same memory and tlb miss happens,
> >> one thread fills pte entry, the other reads new pte value during page fault
> >> handling. PTE value may be updated before page faul, so the process need
> >
> > Fault.
>
> And "needs".
>
> >> need update tlb still.
>
> Oh, and one "need" is enough. :-)
Hmm, "the process need update" looks right to me (compare "the process
need not update") as "need" is used as a modal verb in this sentence.
Alternatively "the process needs to update" could be used (with "need" as
a main verb, and "to" then).
I'm not a native English speaker though, so I might be missing a usage
subtlety here.
NB I'd be in favour of capitalising "PTE" and "TLB" consistently
throughout though as the norm is with acronyms.
Maciej