From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ingo Molnar Date: Mon, 07 Oct 2019 13:51:58 +0000 Subject: Re: [PATCH V4 2/2] mm/pgtable/debug: Add test validating architecture page table helpers Message-Id: <20191007135158.GA36360@gmail.com> List-Id: References: <1570427124-21887-1-git-send-email-anshuman.khandual@arm.com> <1570427124-21887-3-git-send-email-anshuman.khandual@arm.com> <20191007130617.GB56546@gmail.com> <20191007132607.4q537nauwfn5thol@box> In-Reply-To: <20191007132607.4q537nauwfn5thol@box> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: "Kirill A. Shutemov" Cc: Mark Rutland , linux-ia64@vger.kernel.org, linux-sh@vger.kernel.org, Peter Zijlstra , James Hogan , Tetsuo Handa , Heiko Carstens , Michal Hocko , linux-mm@kvack.org, Paul Mackerras , sparclinux@vger.kernel.org, Thomas Gleixner , linux-s390@vger.kernel.org, Michael Ellerman , x86@kernel.org, Russell King - ARM Linux , Matthew Wilcox , Steven Price , Jason Gunthorpe , Gerald Schaefer , linux-snps-arc@lists.infradead.org, linux-arm-kernel@lists.infradead.org, Kees Cook , Anshuman Khandual , Masahiro Yamada , Mark Brown , Dan Williams , Vlastimil Babka , Christophe Leroy , Sri Krishna chowdary , Ard Biesheuvel , Greg Kroah-Hartman , Dave Hansen , linux-mips@vger.kernel.org, Ralf Baechle , linux-kernel@vger.kernel.org, Paul Burton , Mike Rapoport , Vineet Gupta , Martin Schwidefsky , Andrew Morton , linuxppc-dev@lists.ozlabs.org, "David S. Miller" * 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