Re: [PATCH V4 2/2] mm/pgtable/debug: Add test validating architecture page table helpers
On 10/07/2019 07:30 PM, Kirill A. Shutemov wrote:
> On Mon, Oct 07, 2019 at 03:51:58PM +0200, Ingo Molnar wrote:
>>
>> * Kirill A. Shutemov wrote:
>>
>>> On Mon, Oct 07, 2019 at 03:06:17PM +0200, Ingo Molnar wrote:
* Anshuman Khandual wrote:
> This adds a test module which will validate architecture page table
> helpers
> and accessors regarding compliance with generic MM semantics expectations.
> This will help various architectures in validating changes to the existing
> page table helpers or addition of new ones.
>
> Test page table and memory pages creating it's entries at various level
> are
> all allocated from system memory with required alignments. If memory pages
> with required size and alignment could not be allocated, then all
> depending
> individual tests are skipped.
> diff --git a/arch/x86/include/asm/pgtable_64_types.h
> b/arch/x86/include/asm/pgtable_64_types.h
> index 52e5f5f2240d..b882792a3999 100644
> --- a/arch/x86/include/asm/pgtable_64_types.h
> +++ b/arch/x86/include/asm/pgtable_64_types.h
> @@ -40,6 +40,8 @@ static inline bool pgtable_l5_enabled(void)
> #define pgtable_l5_enabled() 0
> #endif /* CONFIG_X86_5LEVEL */
>
> +#define mm_p4d_folded(mm) (!pgtable_l5_enabled())
> +
> extern unsigned int pgdir_shift;
> extern unsigned int ptrs_per_p4d;
Any deep reason this has to be a macro instead of proper C?
>>>
>>> It's a way to override the generic mm_p4d_folded(). It can be rewritten
>>> as inline function + define. Something like:
>>>
>>> #define mm_p4d_folded mm_p4d_folded
>>> static inline bool mm_p4d_folded(struct mm_struct *mm)
>>> {
>>> return !pgtable_l5_enabled();
>>> }
>>>
>>> But I don't see much reason to be more verbose here than needed.
>>
>> C type checking? Documentation? Yeah, I know it's just a one-liner, but
>> the principle of the death by a thousand cuts applies here.
>
> Okay, if you think it worth it. Anshuman, could you fix it up for the next
> submission?
Sure, will do.
>
>
>> BTW., any reason this must be in the low level pgtable_64_types.h type
>> header, instead of one of the API level header files?
>
> I defined it next pgtable_l5_enabled(). What is more appropriate place to
> you? pgtable_64.h? Yeah, it makes sense.
Needs to be moved to arch/x86/include/asm/pgtable_64.h as well ?
Re: [PATCH V4 2/2] mm/pgtable/debug: Add test validating architecture page table helpers
On 10/07/2019 06:36 PM, Ingo Molnar wrote: > > * Anshuman Khandual wrote: > >> This adds a test module which will validate architecture page table helpers >> and accessors regarding compliance with generic MM semantics expectations. >> This will help various architectures in validating changes to the existing >> page table helpers or addition of new ones. >> >> Test page table and memory pages creating it's entries at various level are >> all allocated from system memory with required alignments. If memory pages >> with required size and alignment could not be allocated, then all depending >> individual tests are skipped. > >> diff --git a/arch/x86/include/asm/pgtable_64_types.h >> b/arch/x86/include/asm/pgtable_64_types.h >> index 52e5f5f2240d..b882792a3999 100644 >> --- a/arch/x86/include/asm/pgtable_64_types.h >> +++ b/arch/x86/include/asm/pgtable_64_types.h >> @@ -40,6 +40,8 @@ static inline bool pgtable_l5_enabled(void) >> #define pgtable_l5_enabled() 0 >> #endif /* CONFIG_X86_5LEVEL */ >> >> +#define mm_p4d_folded(mm) (!pgtable_l5_enabled()) >> + >> extern unsigned int pgdir_shift; >> extern unsigned int ptrs_per_p4d; > > Any deep reason this has to be a macro instead of proper C? > >> diff --git a/mm/Kconfig.debug b/mm/Kconfig.debug >> index 327b3ebf23bf..683131b1ee7d 100644 >> --- a/mm/Kconfig.debug >> +++ b/mm/Kconfig.debug >> @@ -117,3 +117,18 @@ config DEBUG_RODATA_TEST >> depends on STRICT_KERNEL_RWX >> ---help--- >>This option enables a testcase for the setting rodata read-only. >> + >> +config DEBUG_ARCH_PGTABLE_TEST >> +bool "Test arch page table helpers for semantics compliance" >> +depends on MMU >> +depends on DEBUG_KERNEL >> +depends on !(ARM || IA64) > > Please add a proper enabling switch for architectures to opt in. Sure, will do. > > Please also add it to Documentation/features/list-arch.sh so that it's > listed as a 'TODO' entry on architectures where the tests are not enabled > yet. Will do. > >> +help >> + This options provides a kernel module which can be used to test >> + architecture page table helper functions on various platform in >> + verifying if they comply with expected generic MM semantics. This >> + will help architectures code in making sure that any changes or >> + new additions of these helpers will still conform to generic MM >> + expected semantics. > > Typos and grammar fixed: > > help > This option provides a kernel module which can be used to test > architecture page table helper functions on various platforms in > verifying if they comply with expected generic MM semantics. This > will help architecture code in making sure that any changes or > new additions of these helpers still conform to expected > semantics of the generic MM. Sure, will update except the 'kernel module' part. Thank you. > > Also, more fundamentally: isn't a kernel module too late for such a debug Its not a kernel module any more, my bad that the description has still these words left on from previous versions, will fix it. The test now gets invoked through a late_initcall(). > check, should something break due to a core MM change? Have these debug > checks caught any bugs or inconsistencies before? Gerald Schaefer had reported earlier about a bug found on s390 with this test. https://lkml.org/lkml/2019/9/4/1718 > > Why not call this as some earlier MM debug check, after enabling paging > but before executing user-space binaries or relying on complex MM ops > within the kernel, called at a stage when those primitives are all > expected to work fine? At minimum we need buddy allocator to be initialized for the allocations to work. Just after pgtable_init() or kmem_cache_init() in mm_init() will be a good place ? > > It seems to me that arch_pgtable_tests_init) won't even context-switch > normally, right? Not sure whether I got this. Why would you expect it to context switch ? > > Finally, instead of inventing yet another randomly named .config debug > switch, please fit it into the regular MM debug options which go along > the CONFIG_DEBUG_VM* naming scheme. > > Might even make sense to enable these new debug checks by default if > CONFIG_DEBUG_VM=y, that way we'll get a *lot* more debug coverage than > some random module somewhere that few people will know about, let alone > run. All the configs with respect to memory debugging is generated from lib/Kconfig.debug after fetching all that is in "mm/Kconfig.debug". There are only three configs which depend on CONFIG_DEBUG_VM like a package. 1. CONFIG_DEBUG_VM_VMACACHE 2. CONFIG_DEBUG_VM_RB 3. CONFIG_DEBUG_VM_PGFLAGS 4. CONFIG_DEBUG_VM_PGTABLE [proposed for this] Before that, just trying to understand whether the reason of making this arch page table test as part of DEBUG_VM_* package than a just a stand alone config as many others, is that it is directly related to
Re: [PATCH V4 2/2] mm/pgtable/debug: Add test validating architecture page table helpers
On Mon, Oct 07, 2019 at 03:51:58PM +0200, Ingo Molnar wrote:
>
> * Kirill A. Shutemov wrote:
>
> > On Mon, Oct 07, 2019 at 03:06:17PM +0200, Ingo Molnar wrote:
> > >
> > > * Anshuman Khandual wrote:
> > >
> > > > This adds a test module which will validate architecture page table
> > > > helpers
> > > > and accessors regarding compliance with generic MM semantics
> > > > expectations.
> > > > This will help various architectures in validating changes to the
> > > > existing
> > > > page table helpers or addition of new ones.
> > > >
> > > > Test page table and memory pages creating it's entries at various level
> > > > are
> > > > all allocated from system memory with required alignments. If memory
> > > > pages
> > > > with required size and alignment could not be allocated, then all
> > > > depending
> > > > individual tests are skipped.
> > >
> > > > diff --git a/arch/x86/include/asm/pgtable_64_types.h
> > > > b/arch/x86/include/asm/pgtable_64_types.h
> > > > index 52e5f5f2240d..b882792a3999 100644
> > > > --- a/arch/x86/include/asm/pgtable_64_types.h
> > > > +++ b/arch/x86/include/asm/pgtable_64_types.h
> > > > @@ -40,6 +40,8 @@ static inline bool pgtable_l5_enabled(void)
> > > > #define pgtable_l5_enabled() 0
> > > > #endif /* CONFIG_X86_5LEVEL */
> > > >
> > > > +#define mm_p4d_folded(mm) (!pgtable_l5_enabled())
> > > > +
> > > > extern unsigned int pgdir_shift;
> > > > extern unsigned int ptrs_per_p4d;
> > >
> > > Any deep reason this has to be a macro instead of proper C?
> >
> > It's a way to override the generic mm_p4d_folded(). It can be rewritten
> > as inline function + define. Something like:
> >
> > #define mm_p4d_folded mm_p4d_folded
> > static inline bool mm_p4d_folded(struct mm_struct *mm)
> > {
> > return !pgtable_l5_enabled();
> > }
> >
> > But I don't see much reason to be more verbose here than needed.
>
> C type checking? Documentation? Yeah, I know it's just a one-liner, but
> the principle of the death by a thousand cuts applies here.
Okay, if you think it worth it. Anshuman, could you fix it up for the next
submission?
> BTW., any reason this must be in the low level pgtable_64_types.h type
> header, instead of one of the API level header files?
I defined it next pgtable_l5_enabled(). What is more appropriate place to
you? pgtable_64.h? Yeah, it makes sense.
--
Kirill A. Shutemov
Re: [PATCH V4 2/2] mm/pgtable/debug: Add test validating architecture page table helpers
* Kirill A. Shutemov wrote:
> On Mon, Oct 07, 2019 at 03:06:17PM +0200, Ingo Molnar wrote:
> >
> > * Anshuman Khandual wrote:
> >
> > > This adds a test module which will validate architecture page table
> > > helpers
> > > and accessors regarding compliance with generic MM semantics expectations.
> > > This will help various architectures in validating changes to the existing
> > > page table helpers or addition of new ones.
> > >
> > > Test page table and memory pages creating it's entries at various level
> > > are
> > > all allocated from system memory with required alignments. If memory pages
> > > with required size and alignment could not be allocated, then all
> > > depending
> > > individual tests are skipped.
> >
> > > diff --git a/arch/x86/include/asm/pgtable_64_types.h
> > > b/arch/x86/include/asm/pgtable_64_types.h
> > > index 52e5f5f2240d..b882792a3999 100644
> > > --- a/arch/x86/include/asm/pgtable_64_types.h
> > > +++ b/arch/x86/include/asm/pgtable_64_types.h
> > > @@ -40,6 +40,8 @@ static inline bool pgtable_l5_enabled(void)
> > > #define pgtable_l5_enabled() 0
> > > #endif /* CONFIG_X86_5LEVEL */
> > >
> > > +#define mm_p4d_folded(mm) (!pgtable_l5_enabled())
> > > +
> > > extern unsigned int pgdir_shift;
> > > extern unsigned int ptrs_per_p4d;
> >
> > Any deep reason this has to be a macro instead of proper C?
>
> It's a way to override the generic mm_p4d_folded(). It can be rewritten
> as inline function + define. Something like:
>
> #define mm_p4d_folded mm_p4d_folded
> static inline bool mm_p4d_folded(struct mm_struct *mm)
> {
> return !pgtable_l5_enabled();
> }
>
> But I don't see much reason to be more verbose here than needed.
C type checking? Documentation? Yeah, I know it's just a one-liner, but
the principle of the death by a thousand cuts applies here.
BTW., any reason this must be in the low level pgtable_64_types.h type
header, instead of one of the API level header files?
Thanks,
Ingo
Re: [PATCH V4 2/2] mm/pgtable/debug: Add test validating architecture page table helpers
On Mon, Oct 07, 2019 at 03:06:17PM +0200, Ingo Molnar wrote:
>
> * Anshuman Khandual wrote:
>
> > This adds a test module which will validate architecture page table helpers
> > and accessors regarding compliance with generic MM semantics expectations.
> > This will help various architectures in validating changes to the existing
> > page table helpers or addition of new ones.
> >
> > Test page table and memory pages creating it's entries at various level are
> > all allocated from system memory with required alignments. If memory pages
> > with required size and alignment could not be allocated, then all depending
> > individual tests are skipped.
>
> > diff --git a/arch/x86/include/asm/pgtable_64_types.h
> > b/arch/x86/include/asm/pgtable_64_types.h
> > index 52e5f5f2240d..b882792a3999 100644
> > --- a/arch/x86/include/asm/pgtable_64_types.h
> > +++ b/arch/x86/include/asm/pgtable_64_types.h
> > @@ -40,6 +40,8 @@ static inline bool pgtable_l5_enabled(void)
> > #define pgtable_l5_enabled() 0
> > #endif /* CONFIG_X86_5LEVEL */
> >
> > +#define mm_p4d_folded(mm) (!pgtable_l5_enabled())
> > +
> > extern unsigned int pgdir_shift;
> > extern unsigned int ptrs_per_p4d;
>
> Any deep reason this has to be a macro instead of proper C?
It's a way to override the generic mm_p4d_folded(). It can be rewritten
as inline function + define. Something like:
#define mm_p4d_folded mm_p4d_folded
static inline bool mm_p4d_folded(struct mm_struct *mm)
{
return !pgtable_l5_enabled();
}
But I don't see much reason to be more verbose here than needed.
--
Kirill A. Shutemov
Re: [PATCH V4 2/2] mm/pgtable/debug: Add test validating architecture page table helpers
* Anshuman Khandual wrote: > This adds a test module which will validate architecture page table helpers > and accessors regarding compliance with generic MM semantics expectations. > This will help various architectures in validating changes to the existing > page table helpers or addition of new ones. > > Test page table and memory pages creating it's entries at various level are > all allocated from system memory with required alignments. If memory pages > with required size and alignment could not be allocated, then all depending > individual tests are skipped. > diff --git a/arch/x86/include/asm/pgtable_64_types.h > b/arch/x86/include/asm/pgtable_64_types.h > index 52e5f5f2240d..b882792a3999 100644 > --- a/arch/x86/include/asm/pgtable_64_types.h > +++ b/arch/x86/include/asm/pgtable_64_types.h > @@ -40,6 +40,8 @@ static inline bool pgtable_l5_enabled(void) > #define pgtable_l5_enabled() 0 > #endif /* CONFIG_X86_5LEVEL */ > > +#define mm_p4d_folded(mm) (!pgtable_l5_enabled()) > + > extern unsigned int pgdir_shift; > extern unsigned int ptrs_per_p4d; Any deep reason this has to be a macro instead of proper C? > diff --git a/mm/Kconfig.debug b/mm/Kconfig.debug > index 327b3ebf23bf..683131b1ee7d 100644 > --- a/mm/Kconfig.debug > +++ b/mm/Kconfig.debug > @@ -117,3 +117,18 @@ config DEBUG_RODATA_TEST > depends on STRICT_KERNEL_RWX > ---help--- >This option enables a testcase for the setting rodata read-only. > + > +config DEBUG_ARCH_PGTABLE_TEST > + bool "Test arch page table helpers for semantics compliance" > + depends on MMU > + depends on DEBUG_KERNEL > + depends on !(ARM || IA64) Please add a proper enabling switch for architectures to opt in. Please also add it to Documentation/features/list-arch.sh so that it's listed as a 'TODO' entry on architectures where the tests are not enabled yet. > + help > + This options provides a kernel module which can be used to test > + architecture page table helper functions on various platform in > + verifying if they comply with expected generic MM semantics. This > + will help architectures code in making sure that any changes or > + new additions of these helpers will still conform to generic MM > + expected semantics. Typos and grammar fixed: help This option provides a kernel module which can be used to test architecture page table helper functions on various platforms in verifying if they comply with expected generic MM semantics. This will help architecture code in making sure that any changes or new additions of these helpers still conform to expected semantics of the generic MM. Also, more fundamentally: isn't a kernel module too late for such a debug check, should something break due to a core MM change? Have these debug checks caught any bugs or inconsistencies before? Why not call this as some earlier MM debug check, after enabling paging but before executing user-space binaries or relying on complex MM ops within the kernel, called at a stage when those primitives are all expected to work fine? It seems to me that arch_pgtable_tests_init) won't even context-switch normally, right? Finally, instead of inventing yet another randomly named .config debug switch, please fit it into the regular MM debug options which go along the CONFIG_DEBUG_VM* naming scheme. Might even make sense to enable these new debug checks by default if CONFIG_DEBUG_VM=y, that way we'll get a *lot* more debug coverage than some random module somewhere that few people will know about, let alone run. Thanks, Ingo
[PATCH V4 2/2] mm/pgtable/debug: Add test validating architecture page table helpers
This adds a test module which will validate architecture page table helpers and accessors regarding compliance with generic MM semantics expectations. This will help various architectures in validating changes to the existing page table helpers or addition of new ones. Test page table and memory pages creating it's entries at various level are all allocated from system memory with required alignments. If memory pages with required size and alignment could not be allocated, then all depending individual tests are skipped. Cc: Andrew Morton Cc: Vlastimil Babka Cc: Greg Kroah-Hartman Cc: Thomas Gleixner Cc: Mike Rapoport Cc: Jason Gunthorpe Cc: Dan Williams Cc: Peter Zijlstra Cc: Michal Hocko Cc: Mark Rutland Cc: Mark Brown Cc: Steven Price Cc: Ard Biesheuvel Cc: Masahiro Yamada Cc: Kees Cook Cc: Tetsuo Handa Cc: Matthew Wilcox Cc: Sri Krishna chowdary Cc: Dave Hansen Cc: Russell King - ARM Linux Cc: Michael Ellerman Cc: Paul Mackerras Cc: Martin Schwidefsky Cc: Heiko Carstens Cc: "David S. Miller" Cc: Vineet Gupta Cc: James Hogan Cc: Paul Burton Cc: Ralf Baechle Cc: Kirill A. Shutemov Cc: Gerald Schaefer Cc: Christophe Leroy Cc: linux-snps-...@lists.infradead.org Cc: linux-m...@vger.kernel.org Cc: linux-arm-ker...@lists.infradead.org Cc: linux-i...@vger.kernel.org Cc: linuxppc-dev@lists.ozlabs.org Cc: linux-s...@vger.kernel.org Cc: linux...@vger.kernel.org Cc: sparcli...@vger.kernel.org Cc: x...@kernel.org Cc: linux-ker...@vger.kernel.org Suggested-by: Catalin Marinas Signed-off-by: Christophe Leroy Tested-by: Christophe Leroy#PPC32 Signed-off-by: Anshuman Khandual --- arch/x86/include/asm/pgtable_64_types.h | 2 + mm/Kconfig.debug| 15 + mm/Makefile | 1 + mm/arch_pgtable_test.c | 440 4 files changed, 458 insertions(+) create mode 100644 mm/arch_pgtable_test.c diff --git a/arch/x86/include/asm/pgtable_64_types.h b/arch/x86/include/asm/pgtable_64_types.h index 52e5f5f2240d..b882792a3999 100644 --- a/arch/x86/include/asm/pgtable_64_types.h +++ b/arch/x86/include/asm/pgtable_64_types.h @@ -40,6 +40,8 @@ static inline bool pgtable_l5_enabled(void) #define pgtable_l5_enabled() 0 #endif /* CONFIG_X86_5LEVEL */ +#define mm_p4d_folded(mm) (!pgtable_l5_enabled()) + extern unsigned int pgdir_shift; extern unsigned int ptrs_per_p4d; diff --git a/mm/Kconfig.debug b/mm/Kconfig.debug index 327b3ebf23bf..683131b1ee7d 100644 --- a/mm/Kconfig.debug +++ b/mm/Kconfig.debug @@ -117,3 +117,18 @@ config DEBUG_RODATA_TEST depends on STRICT_KERNEL_RWX ---help--- This option enables a testcase for the setting rodata read-only. + +config DEBUG_ARCH_PGTABLE_TEST + bool "Test arch page table helpers for semantics compliance" + depends on MMU + depends on DEBUG_KERNEL + depends on !(ARM || IA64) + help + This options provides a kernel module which can be used to test + architecture page table helper functions on various platform in + verifying if they comply with expected generic MM semantics. This + will help architectures code in making sure that any changes or + new additions of these helpers will still conform to generic MM + expected semantics. + + If unsure, say N. diff --git a/mm/Makefile b/mm/Makefile index d996846697ef..bb572c5aa8c5 100644 --- a/mm/Makefile +++ b/mm/Makefile @@ -86,6 +86,7 @@ obj-$(CONFIG_HWPOISON_INJECT) += hwpoison-inject.o obj-$(CONFIG_DEBUG_KMEMLEAK) += kmemleak.o obj-$(CONFIG_DEBUG_KMEMLEAK_TEST) += kmemleak-test.o obj-$(CONFIG_DEBUG_RODATA_TEST) += rodata_test.o +obj-$(CONFIG_DEBUG_ARCH_PGTABLE_TEST) += arch_pgtable_test.o obj-$(CONFIG_PAGE_OWNER) += page_owner.o obj-$(CONFIG_CLEANCACHE) += cleancache.o obj-$(CONFIG_MEMORY_ISOLATION) += page_isolation.o diff --git a/mm/arch_pgtable_test.c b/mm/arch_pgtable_test.c new file mode 100644 index ..2942a0484d63 --- /dev/null +++ b/mm/arch_pgtable_test.c @@ -0,0 +1,440 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * This kernel module validates architecture page table helpers & + * accessors and helps in verifying their continued compliance with + * generic MM semantics. + * + * Copyright (C) 2019 ARM Ltd. + * + * Author: Anshuman Khandual + */ +#define pr_fmt(fmt) "arch_pgtable_test: %s " fmt, __func__ + +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +/* + * Basic operations + * + * mkold(entry)= An old and not a young entry + * mkyoung(entry) = A young and not an old entry + * mkdirty(entry) = A dirty and not a clean entry + * mkclean(entry) = A clean and not a dirty entry + * mkwrite(entry) = A write and not a write protected entry + *
