| Message ID | 20240306104147.193052-10-peterx@redhat.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | mm/treewide: Remove pXd_huge() API | expand |
peterx@redhat.com writes: > From: Peter Xu <peterx@redhat.com> > > PowerPC book3s 4K mostly has the same definition on both, except pXd_huge() > constantly returns 0 for hash MMUs. AFAICT that is fine to be removed, > because pXd_huge() reflects a hugetlb entry, while it's own hugetlb pgtable > lookup function (__find_linux_pte() shared by all powerpc code) already use > pXd_leaf() irrelevant of the MMU type. It means pXd_leaf() should work all > fine with hash MMU pgtables or something could already went wrong. Yes I think that's correct. 4K Hash MMU doesn't support any hugepage size at PMD or PUD level (the geometry is wrong), so pmd/pud_huge() were written with that in mind, ie. they are hard coded to return false. But it should be OK to use pmd/pud_leaf(), they will actually look for _PAGE_PTE, but it should never be set for 4K Hash. See eg. arch/powerpc/include/asm/book3s/64/hash-4k.h: static inline pmd_t hash__pmd_mkhuge(pmd_t pmd) { BUG(); return pmd; } > The goal should be that we will have one API pXd_leaf() to detect all kinds > of huge mappings. AFAICT we need to use the pXd_leaf() impl (rather than > pXd_huge() ones) to make sure ie. THPs on hash MMU will also return true. > > This helps to simplify a follow up patch to drop pXd_huge() treewide. > > Cc: Michael Ellerman <mpe@ellerman.id.au> > Cc: Nicholas Piggin <npiggin@gmail.com> > Cc: Christophe Leroy <christophe.leroy@csgroup.eu> > Cc: "Aneesh Kumar K.V" <aneesh.kumar@kernel.org> > Cc: "Naveen N. Rao" <naveen.n.rao@linux.ibm.com> > Cc: linuxppc-dev@lists.ozlabs.org > Signed-off-by: Peter Xu <peterx@redhat.com> > --- > arch/powerpc/include/asm/book3s/64/pgtable-4k.h | 14 ++------------ > 1 file changed, 2 insertions(+), 12 deletions(-) > > diff --git a/arch/powerpc/include/asm/book3s/64/pgtable-4k.h b/arch/powerpc/include/asm/book3s/64/pgtable-4k.h > index 48f21820afe2..92545981bb49 100644 > --- a/arch/powerpc/include/asm/book3s/64/pgtable-4k.h > +++ b/arch/powerpc/include/asm/book3s/64/pgtable-4k.h > @@ -8,22 +8,12 @@ > #ifdef CONFIG_HUGETLB_PAGE > static inline int pmd_huge(pmd_t pmd) > { > - /* > - * leaf pte for huge page > - */ > - if (radix_enabled()) > - return !!(pmd_raw(pmd) & cpu_to_be64(_PAGE_PTE)); > - return 0; > + return pmd_leaf(pmd); > } > > static inline int pud_huge(pud_t pud) > { > - /* > - * leaf pte for huge page > - */ > - if (radix_enabled()) > - return !!(pud_raw(pud) & cpu_to_be64(_PAGE_PTE)); > - return 0; > + return pud_leaf(pud); > } This doesn't actually compile though. arch/powerpc/include/asm/book3s/64/pgtable-4k.h:11:16: error: implicit declaration of function ‘pmd_leaf’; did you mean ‘pgd_clear’? [-Werror=implicit-function-declaration] etc. To make it compile we'd need to relocate the pmd/pud_leaf() definitions: diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h b/arch/powerpc/include/asm/book3s/64/pgtable.h index df66dce8306f..fd7180fded75 100644 --- a/arch/powerpc/include/asm/book3s/64/pgtable.h +++ b/arch/powerpc/include/asm/book3s/64/pgtable.h @@ -262,6 +262,18 @@ extern unsigned long __kernel_io_end; extern struct page *vmemmap; extern unsigned long pci_io_base; + +#define pmd_leaf pmd_leaf +static inline bool pmd_leaf(pmd_t pmd) +{ + return !!(pmd_raw(pmd) & cpu_to_be64(_PAGE_PTE)); +} + +#define pud_leaf pud_leaf +static inline bool pud_leaf(pud_t pud) +{ + return !!(pud_raw(pud) & cpu_to_be64(_PAGE_PTE)); +} #endif /* __ASSEMBLY__ */ #include <asm/book3s/64/hash.h> @@ -1436,20 +1448,5 @@ static inline bool is_pte_rw_upgrade(unsigned long old_val, unsigned long new_va return false; } -/* - * Like pmd_huge(), but works regardless of config options - */ -#define pmd_leaf pmd_leaf -static inline bool pmd_leaf(pmd_t pmd) -{ - return !!(pmd_raw(pmd) & cpu_to_be64(_PAGE_PTE)); -} - -#define pud_leaf pud_leaf -static inline bool pud_leaf(pud_t pud) -{ - return !!(pud_raw(pud) & cpu_to_be64(_PAGE_PTE)); -} - #endif /* __ASSEMBLY__ */ #endif /* _ASM_POWERPC_BOOK3S_64_PGTABLE_H_ */ cheers
On Wed, Mar 06, 2024 at 11:56:56PM +1100, Michael Ellerman wrote: > peterx@redhat.com writes: > > From: Peter Xu <peterx@redhat.com> > > > > PowerPC book3s 4K mostly has the same definition on both, except pXd_huge() > > constantly returns 0 for hash MMUs. AFAICT that is fine to be removed, > > because pXd_huge() reflects a hugetlb entry, while it's own hugetlb pgtable > > lookup function (__find_linux_pte() shared by all powerpc code) already use > > pXd_leaf() irrelevant of the MMU type. It means pXd_leaf() should work all > > fine with hash MMU pgtables or something could already went wrong. > > Yes I think that's correct. > > 4K Hash MMU doesn't support any hugepage size at PMD or PUD level (the > geometry is wrong), so pmd/pud_huge() were written with that in mind, > ie. they are hard coded to return false. > > But it should be OK to use pmd/pud_leaf(), they will actually look for > _PAGE_PTE, but it should never be set for 4K Hash. > > See eg. arch/powerpc/include/asm/book3s/64/hash-4k.h: > > static inline pmd_t hash__pmd_mkhuge(pmd_t pmd) > { > BUG(); > return pmd; > } Good to get confirmation on this, thanks, Michael. These explanations also look better than what I wrote, I'll amend the commit message. > > > The goal should be that we will have one API pXd_leaf() to detect all kinds > > of huge mappings. AFAICT we need to use the pXd_leaf() impl (rather than > > pXd_huge() ones) to make sure ie. THPs on hash MMU will also return true. > > > > This helps to simplify a follow up patch to drop pXd_huge() treewide. > > > > Cc: Michael Ellerman <mpe@ellerman.id.au> > > Cc: Nicholas Piggin <npiggin@gmail.com> > > Cc: Christophe Leroy <christophe.leroy@csgroup.eu> > > Cc: "Aneesh Kumar K.V" <aneesh.kumar@kernel.org> > > Cc: "Naveen N. Rao" <naveen.n.rao@linux.ibm.com> > > Cc: linuxppc-dev@lists.ozlabs.org > > Signed-off-by: Peter Xu <peterx@redhat.com> > > --- > > arch/powerpc/include/asm/book3s/64/pgtable-4k.h | 14 ++------------ > > 1 file changed, 2 insertions(+), 12 deletions(-) > > > > diff --git a/arch/powerpc/include/asm/book3s/64/pgtable-4k.h b/arch/powerpc/include/asm/book3s/64/pgtable-4k.h > > index 48f21820afe2..92545981bb49 100644 > > --- a/arch/powerpc/include/asm/book3s/64/pgtable-4k.h > > +++ b/arch/powerpc/include/asm/book3s/64/pgtable-4k.h > > @@ -8,22 +8,12 @@ > > #ifdef CONFIG_HUGETLB_PAGE > > static inline int pmd_huge(pmd_t pmd) > > { > > - /* > > - * leaf pte for huge page > > - */ > > - if (radix_enabled()) > > - return !!(pmd_raw(pmd) & cpu_to_be64(_PAGE_PTE)); > > - return 0; > > + return pmd_leaf(pmd); > > } > > > > static inline int pud_huge(pud_t pud) > > { > > - /* > > - * leaf pte for huge page > > - */ > > - if (radix_enabled()) > > - return !!(pud_raw(pud) & cpu_to_be64(_PAGE_PTE)); > > - return 0; > > + return pud_leaf(pud); > > } > > This doesn't actually compile though. > > arch/powerpc/include/asm/book3s/64/pgtable-4k.h:11:16: error: implicit declaration of function ‘pmd_leaf’; did you mean ‘pgd_clear’? [-Werror=implicit-function-declaration] > > etc. > > To make it compile we'd need to relocate the pmd/pud_leaf() definitions: > > diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h b/arch/powerpc/include/asm/book3s/64/pgtable.h > index df66dce8306f..fd7180fded75 100644 > --- a/arch/powerpc/include/asm/book3s/64/pgtable.h > +++ b/arch/powerpc/include/asm/book3s/64/pgtable.h > @@ -262,6 +262,18 @@ extern unsigned long __kernel_io_end; > > extern struct page *vmemmap; > extern unsigned long pci_io_base; > + > +#define pmd_leaf pmd_leaf > +static inline bool pmd_leaf(pmd_t pmd) > +{ > + return !!(pmd_raw(pmd) & cpu_to_be64(_PAGE_PTE)); > +} > + > +#define pud_leaf pud_leaf > +static inline bool pud_leaf(pud_t pud) > +{ > + return !!(pud_raw(pud) & cpu_to_be64(_PAGE_PTE)); > +} > #endif /* __ASSEMBLY__ */ > > #include <asm/book3s/64/hash.h> > @@ -1436,20 +1448,5 @@ static inline bool is_pte_rw_upgrade(unsigned long old_val, unsigned long new_va > return false; > } > > -/* > - * Like pmd_huge(), but works regardless of config options > - */ > -#define pmd_leaf pmd_leaf > -static inline bool pmd_leaf(pmd_t pmd) > -{ > - return !!(pmd_raw(pmd) & cpu_to_be64(_PAGE_PTE)); > -} > - > -#define pud_leaf pud_leaf > -static inline bool pud_leaf(pud_t pud) > -{ > - return !!(pud_raw(pud) & cpu_to_be64(_PAGE_PTE)); > -} > - > #endif /* __ASSEMBLY__ */ > #endif /* _ASM_POWERPC_BOOK3S_64_PGTABLE_H_ */ Thanks for the help, I'll fix that. I'm wondering when syzbot will start to feed my series into the testers; I do still rely on those feedbacks on compilation issues with such treewide changes, but so far I didn't yet receive any reports. I've also attached the new patch directly here in case of any further comment. Thanks, ==========8<=========== From 9e75aef2141170f241577e7786aaa4bbbfd93360 Mon Sep 17 00:00:00 2001 From: Peter Xu <peterx@redhat.com> Date: Wed, 6 Mar 2024 14:49:48 +0800 Subject: [PATCH] mm/powerpc: Redefine pXd_huge() with pXd_leaf() PowerPC book3s 4K mostly has the same definition on both, except pXd_huge() constantly returns 0 for hash MMUs. As Michael Ellerman pointed out [1], it is safe to check _PAGE_PTE on hash MMUs, as the bit will never be set so it will keep returning false. As a reference, __p[mu]d_mkhuge() will trigger a BUG_ON trying to create such huge mappings for 4K hash MMUs. Meanwhile, the major powerpc hugetlb pgtable walker __find_linux_pte(), already used pXd_leaf() to check hugetlb mappings. The goal should be that we will have one API pXd_leaf() to detect all kinds of huge mappings. AFAICT we need to use the pXd_leaf() impl (rather than pXd_huge() ones) to make sure ie. THPs on hash MMU will also return true. This helps to simplify a follow up patch to drop pXd_huge() treewide. NOTE: *_leaf() definition need to be moved before the inclusion of asm/book3s/64/pgtable-4k.h, which defines pXd_huge() with it. [1] https://lore.kernel.org/r/87v85zo6w7.fsf@mail.lhotse Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Nicholas Piggin <npiggin@gmail.com> Cc: Christophe Leroy <christophe.leroy@csgroup.eu> Cc: "Aneesh Kumar K.V" <aneesh.kumar@kernel.org> Cc: "Naveen N. Rao" <naveen.n.rao@linux.ibm.com> Cc: linuxppc-dev@lists.ozlabs.org Signed-off-by: Peter Xu <peterx@redhat.com> --- .../include/asm/book3s/64/pgtable-4k.h | 14 ++-------- arch/powerpc/include/asm/book3s/64/pgtable.h | 27 +++++++++---------- 2 files changed, 14 insertions(+), 27 deletions(-) diff --git a/arch/powerpc/include/asm/book3s/64/pgtable-4k.h b/arch/powerpc/include/asm/book3s/64/pgtable-4k.h index 48f21820afe2..92545981bb49 100644 --- a/arch/powerpc/include/asm/book3s/64/pgtable-4k.h +++ b/arch/powerpc/include/asm/book3s/64/pgtable-4k.h @@ -8,22 +8,12 @@ #ifdef CONFIG_HUGETLB_PAGE static inline int pmd_huge(pmd_t pmd) { - /* - * leaf pte for huge page - */ - if (radix_enabled()) - return !!(pmd_raw(pmd) & cpu_to_be64(_PAGE_PTE)); - return 0; + return pmd_leaf(pmd); } static inline int pud_huge(pud_t pud) { - /* - * leaf pte for huge page - */ - if (radix_enabled()) - return !!(pud_raw(pud) & cpu_to_be64(_PAGE_PTE)); - return 0; + return pud_leaf(pud); } /* diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h b/arch/powerpc/include/asm/book3s/64/pgtable.h index df66dce8306f..fd7180fded75 100644 --- a/arch/powerpc/include/asm/book3s/64/pgtable.h +++ b/arch/powerpc/include/asm/book3s/64/pgtable.h @@ -262,6 +262,18 @@ extern unsigned long __kernel_io_end; extern struct page *vmemmap; extern unsigned long pci_io_base; + +#define pmd_leaf pmd_leaf +static inline bool pmd_leaf(pmd_t pmd) +{ + return !!(pmd_raw(pmd) & cpu_to_be64(_PAGE_PTE)); +} + +#define pud_leaf pud_leaf +static inline bool pud_leaf(pud_t pud) +{ + return !!(pud_raw(pud) & cpu_to_be64(_PAGE_PTE)); +} #endif /* __ASSEMBLY__ */ #include <asm/book3s/64/hash.h> @@ -1436,20 +1448,5 @@ static inline bool is_pte_rw_upgrade(unsigned long old_val, unsigned long new_va return false; } -/* - * Like pmd_huge(), but works regardless of config options - */ -#define pmd_leaf pmd_leaf -static inline bool pmd_leaf(pmd_t pmd) -{ - return !!(pmd_raw(pmd) & cpu_to_be64(_PAGE_PTE)); -} - -#define pud_leaf pud_leaf -static inline bool pud_leaf(pud_t pud) -{ - return !!(pud_raw(pud) & cpu_to_be64(_PAGE_PTE)); -} - #endif /* __ASSEMBLY__ */ #endif /* _ASM_POWERPC_BOOK3S_64_PGTABLE_H_ */
diff --git a/arch/powerpc/include/asm/book3s/64/pgtable-4k.h b/arch/powerpc/include/asm/book3s/64/pgtable-4k.h index 48f21820afe2..92545981bb49 100644 --- a/arch/powerpc/include/asm/book3s/64/pgtable-4k.h +++ b/arch/powerpc/include/asm/book3s/64/pgtable-4k.h @@ -8,22 +8,12 @@ #ifdef CONFIG_HUGETLB_PAGE static inline int pmd_huge(pmd_t pmd) { - /* - * leaf pte for huge page - */ - if (radix_enabled()) - return !!(pmd_raw(pmd) & cpu_to_be64(_PAGE_PTE)); - return 0; + return pmd_leaf(pmd); } static inline int pud_huge(pud_t pud) { - /* - * leaf pte for huge page - */ - if (radix_enabled()) - return !!(pud_raw(pud) & cpu_to_be64(_PAGE_PTE)); - return 0; + return pud_leaf(pud); } /*