When a pmd entry is invalidated by pmd_mkinvalid,pmd_present should
return true.
So introduce a _PMD_PRESENT_INVALID_SHIFT bit to check if a pmd is
present but invalidated by pmd_mkinvalid.
Reported-by: kernel test robot <[email protected]>
Signed-off-by: Hongchen Zhang <[email protected]>
---
arch/mips/include/asm/pgtable-64.h | 2 +-
arch/mips/include/asm/pgtable-bits.h | 2 ++
arch/mips/include/asm/pgtable.h | 3 +++
3 files changed, 6 insertions(+), 1 deletion(-)
diff --git a/arch/mips/include/asm/pgtable-64.h b/arch/mips/include/asm/pgtable-64.h
index 41921ac..050cf66 100644
--- a/arch/mips/include/asm/pgtable-64.h
+++ b/arch/mips/include/asm/pgtable-64.h
@@ -265,7 +265,7 @@ static inline int pmd_present(pmd_t pmd)
{
#ifdef CONFIG_MIPS_HUGE_TLB_SUPPORT
if (unlikely(pmd_val(pmd) & _PAGE_HUGE))
- return pmd_val(pmd) & _PAGE_PRESENT;
+ return pmd_val(pmd) & (_PAGE_PRESENT | _PMD_PRESENT_INVALID);
#endif
return pmd_val(pmd) != (unsigned long) invalid_pte_table;
diff --git a/arch/mips/include/asm/pgtable-bits.h b/arch/mips/include/asm/pgtable-bits.h
index 2362842..72cd88a 100644
--- a/arch/mips/include/asm/pgtable-bits.h
+++ b/arch/mips/include/asm/pgtable-bits.h
@@ -130,6 +130,7 @@ enum pgtable_bits {
_PAGE_MODIFIED_SHIFT,
#if defined(CONFIG_MIPS_HUGE_TLB_SUPPORT)
_PAGE_HUGE_SHIFT,
+ _PMD_PRESENT_INVALID_SHIFT,
#endif
#if defined(CONFIG_ARCH_HAS_PTE_SPECIAL)
_PAGE_SPECIAL_SHIFT,
@@ -157,6 +158,7 @@ enum pgtable_bits {
#define _PAGE_MODIFIED (1 << _PAGE_MODIFIED_SHIFT)
#if defined(CONFIG_MIPS_HUGE_TLB_SUPPORT)
# define _PAGE_HUGE (1 << _PAGE_HUGE_SHIFT)
+#define _PMD_PRESENT_INVALID (1 << _PMD_PRESENT_INVALID_SHIFT)
#endif
#if defined(CONFIG_ARCH_HAS_PTE_SPECIAL)
# define _PAGE_SPECIAL (1 << _PAGE_SPECIAL_SHIFT)
diff --git a/arch/mips/include/asm/pgtable.h b/arch/mips/include/asm/pgtable.h
index 374c632..a75f461 100644
--- a/arch/mips/include/asm/pgtable.h
+++ b/arch/mips/include/asm/pgtable.h
@@ -696,12 +696,15 @@ static inline pmd_t pmd_modify(pmd_t pmd, pgprot_t newprot)
return pmd;
}
+#ifdef CONFIG_MIPS_HUGE_TLB_SUPPORT
static inline pmd_t pmd_mkinvalid(pmd_t pmd)
{
+ pmd_val(pmd) |= _PMD_PRESENT_INVALID;
pmd_val(pmd) &= ~(_PAGE_PRESENT | _PAGE_VALID | _PAGE_DIRTY);
return pmd;
}
+#endif
/*
* The generic version pmdp_huge_get_and_clear uses a version of pmd_clear() with a
--
1.8.3.1
On Thu, Jul 07, 2022 at 04:11:35PM +0800, Hongchen Zhang wrote:
> When a pmd entry is invalidated by pmd_mkinvalid,pmd_present should
> return true.
> So introduce a _PMD_PRESENT_INVALID_SHIFT bit to check if a pmd is
> present but invalidated by pmd_mkinvalid.
What problem are you trying to fix ? What are the symptoms ?
> Reported-by: kernel test robot <[email protected]>
the test robot showed problems with your last version of the patch,
which hasn't been integrated into at least the MIPS tree, so no
need to that.
Thomas.
--
Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
good idea. [ RFC1925, 2.3 ]
On 2022/7/7 下午5:22, Thomas Bogendoerfer wrote:
> On Thu, Jul 07, 2022 at 04:11:35PM +0800, Hongchen Zhang wrote:
>> When a pmd entry is invalidated by pmd_mkinvalid,pmd_present should
>> return true.
>> So introduce a _PMD_PRESENT_INVALID_SHIFT bit to check if a pmd is
>> present but invalidated by pmd_mkinvalid.
>
> What problem are you trying to fix ? What are the symptoms ?
>
>> Reported-by: kernel test robot <[email protected]>
>
> the test robot showed problems with your last version of the patch,
> which hasn't been integrated into at least the MIPS tree, so no
> need to that.
>
> Thomas.
>
Hi Thomas,
The idea come from the commit:
b65399f6111b(arm64/mm: Change THP helpers to comply with generic MM
semantics).
There is an problem now:
CPU 0 CPU 1
pmdp_invalidate do_page_fault
... __handle_mm_fault
is_swap_pmd == true
trigger VM_BUG_ON() ?
set_pmd_at
the reason is that pmd_present return true,after this commit
pmd_present will return false,and the VM_BUG_ON will not be triggered.
Like arm64 does,we can introduce a new bit to fix this.
Thanks.
On 2022/7/7 下午7:12, Hongchen Zhang wrote:
> On 2022/7/7 下午5:22, Thomas Bogendoerfer wrote:
>> On Thu, Jul 07, 2022 at 04:11:35PM +0800, Hongchen Zhang wrote:
>>> When a pmd entry is invalidated by pmd_mkinvalid,pmd_present should
>>> return true.
>>> So introduce a _PMD_PRESENT_INVALID_SHIFT bit to check if a pmd is
>>> present but invalidated by pmd_mkinvalid.
>>
>> What problem are you trying to fix ? What are the symptoms ?
>>
>>> Reported-by: kernel test robot <[email protected]>
>>
>> the test robot showed problems with your last version of the patch,
>> which hasn't been integrated into at least the MIPS tree, so no
>> need to that.
>>
>> Thomas.
>>
>
> Hi Thomas,
> The idea come from the commit:
> b65399f6111b(arm64/mm: Change THP helpers to comply with generic MM
> semantics).
> There is an problem now:
> CPU 0 CPU 1
> pmdp_invalidate do_page_fault
> ... __handle_mm_fault
> is_swap_pmd == true
> trigger VM_BUG_ON() ?
> set_pmd_at
> the reason is that pmd_present return true,after this commit
> pmd_present will return false,and the VM_BUG_ON will not be triggered.
> Like arm64 does,we can introduce a new bit to fix this.
>
> Thanks.
Hi Thomas,
Is there problem of this patch? What's your opinion of this patch?
Thanks
On Tue, Jul 12, 2022 at 06:01:08PM +0800, Hongchen Zhang wrote:
> On 2022/7/7 下午7:12, Hongchen Zhang wrote:
> > On 2022/7/7 下午5:22, Thomas Bogendoerfer wrote:
> > > On Thu, Jul 07, 2022 at 04:11:35PM +0800, Hongchen Zhang wrote:
> > > > When a pmd entry is invalidated by pmd_mkinvalid,pmd_present should
> > > > return true.
> > > > So introduce a _PMD_PRESENT_INVALID_SHIFT bit to check if a pmd is
> > > > present but invalidated by pmd_mkinvalid.
> > >
> > > What problem are you trying to fix ? What are the symptoms ?
> > >
> > > > Reported-by: kernel test robot <[email protected]>
> > >
> > > the test robot showed problems with your last version of the patch,
> > > which hasn't been integrated into at least the MIPS tree, so no
> > > need to that.
> > >
> > > Thomas.
> > >
> >
> > Hi Thomas,
> > The idea come from the commit:
> > b65399f6111b(arm64/mm: Change THP helpers to comply with generic MM
> > semantics).
> > There is an problem now:
> > CPU 0 CPU 1
> > pmdp_invalidate do_page_fault
> > ... __handle_mm_fault
> > is_swap_pmd == true
> > trigger VM_BUG_ON() ?
> > set_pmd_at
> > the reason is that pmd_present return true,after this commit
> > pmd_present will return false,and the VM_BUG_ON will not be triggered.
> > Like arm64 does,we can introduce a new bit to fix this.
> >
> > Thanks.
> Hi Thomas,
> Is there problem of this patch? What's your opinion of this patch?
I haven't dig deeper into it, but needing more page bits is a pain
for 32bit kernel and would make it nearly impossible to get huge
page support there. And the description you gave me, needs to be
in the commit description.
Thomas.
--
Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
good idea. [ RFC1925, 2.3 ]
On 2022/7/12 下午7:19, Thomas Bogendoerfer wrote:
> On Tue, Jul 12, 2022 at 06:01:08PM +0800, Hongchen Zhang wrote:
>> On 2022/7/7 下午7:12, Hongchen Zhang wrote:
>>> On 2022/7/7 下午5:22, Thomas Bogendoerfer wrote:
>>>> On Thu, Jul 07, 2022 at 04:11:35PM +0800, Hongchen Zhang wrote:
>>>>> When a pmd entry is invalidated by pmd_mkinvalid,pmd_present should
>>>>> return true.
>>>>> So introduce a _PMD_PRESENT_INVALID_SHIFT bit to check if a pmd is
>>>>> present but invalidated by pmd_mkinvalid.
>>>>
>>>> What problem are you trying to fix ? What are the symptoms ?
>>>>
>>>>> Reported-by: kernel test robot <[email protected]>
>>>>
>>>> the test robot showed problems with your last version of the patch,
>>>> which hasn't been integrated into at least the MIPS tree, so no
>>>> need to that.
>>>>
>>>> Thomas.
>>>>
>>>
>>> Hi Thomas,
>>> The idea come from the commit:
>>> b65399f6111b(arm64/mm: Change THP helpers to comply with generic MM
>>> semantics).
>>> There is an problem now:
>>> CPU 0 CPU 1
>>> pmdp_invalidate do_page_fault
>>> ... __handle_mm_fault
>>> is_swap_pmd == true
>>> trigger VM_BUG_ON() ?
>>> set_pmd_at
>>> the reason is that pmd_present return true,after this commit
>>> pmd_present will return false,and the VM_BUG_ON will not be triggered.
>>> Like arm64 does,we can introduce a new bit to fix this.
>>>
>>> Thanks.
>> Hi Thomas,
>> Is there problem of this patch? What's your opinion of this patch?
>
> I haven't dig deeper into it, but needing more page bits is a pain
> for 32bit kernel and would make it nearly impossible to get huge
> page support there. And the description you gave me, needs to be
> in the commit description.
>
> Thomas.
>
Hi Thomas,
Thanks for your patiently review. For your question,
1. I think there may be problem when compile 32bit kernel with huge
page support,because _PAGE_HUGE_SHIFT is only defined for R4K now.
2. I will modify the commit as you said and make a v2 patch.
Thanks.
Hongchen Zhang