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(-)
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 <lkp@intel.com>
Signed-off-by: Hongchen Zhang <zhanghongchen@loongson.cn>
---
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
--
1.8.3.1On 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 <lkp@intel.com> 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 <lkp@intel.com> > > 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 <lkp@intel.com> >> >> 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 <lkp@intel.com> > > > > > > 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 <lkp@intel.com> >>>> >>>> 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
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