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[66.187.233.206]) by smtp.gmail.com with ESMTPSA id n132sm9814556qke.58.2020.02.03.07.48.15 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 03 Feb 2020 07:48:18 -0800 (PST) Message-ID: <1580744894.7365.3.camel@lca.pw> Subject: Re: [PATCH V12] mm/debug: Add tests validating architecture page table helpers From: Qian Cai To: Christophe Leroy Cc: Anshuman Khandual , linux-mm@kvack.org, Andrew Morton , Vlastimil Babka , Greg Kroah-Hartman , Thomas Gleixner , Mike Rapoport , Jason Gunthorpe , Dan Williams , Peter Zijlstra , Michal Hocko , Mark Rutland , Mark Brown , Steven Price , Ard Biesheuvel , Masahiro Yamada , Kees Cook , Tetsuo Handa , Matthew Wilcox , Sri Krishna chowdary , Dave Hansen , Russell King - ARM Linux , Michael Ellerman , Paul Mackerras , Martin Schwidefsky , Heiko Carstens , "David S. Miller" , Vineet Gupta , James Hogan , Paul Burton , Ralf Baechle , "Kirill A . Shutemov" , Gerald Schaefer , Ingo Molnar , linux-snps-arc@lists.infradead.org, linux-mips@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-ia64@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, sparclinux@vger.kernel.org, x86@kernel.org, linux-kernel@vger.kernel.org, kasan-dev Date: Mon, 03 Feb 2020 10:48:14 -0500 In-Reply-To: <8e94a073-4045-89aa-6a3b-24847ad7c858@c-s.fr> References: <473d8198-3ac4-af3b-e2ec-c0698a3565d3@c-s.fr> <2C4ADFAE-7BB4-42B7-8F54-F036EA7A4316@lca.pw> <8e94a073-4045-89aa-6a3b-24847ad7c858@c-s.fr> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.22.6 (3.22.6-10.el7) Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, 2020-02-03 at 16:14 +0100, Christophe Leroy wrote: >=20 > Le 02/02/2020 =C3=A0 12:26, Qian Cai a =C3=A9crit=C2=A0: > >=20 > >=20 > > > On Jan 30, 2020, at 9:13 AM, Christophe Leroy wrote: > > >=20 > > > config DEBUG_VM_PGTABLE > > > bool "Debug arch page table for semantics compliance" if ARCH_H= AS_DEBUG_VM_PGTABLE || EXPERT > > > depends on MMU > > > default 'n' if !ARCH_HAS_DEBUG_VM_PGTABLE > > > default 'y' if DEBUG_VM > >=20 > > Does it really necessary to potentially force all bots to run this? S= yzbot, kernel test robot etc? Does it ever pay off for all their machine = times there? > >=20 >=20 > Machine time ? >=20 > On a 32 bits powerpc running at 132 MHz, the tests takes less than 10ms= .=20 > Is it worth taking the risk of not detecting faults by not selecting it= =20 > by default ? The risk is quite low as Catalin mentioned this thing is not to detect regressions but rather for arch/mm maintainers. I do appreciate the efforts to get everyone as possible to run this thing= , so it get more notices once it is broken. However, DEBUG_VM seems like su= ch a generic Kconfig those days that have even been enabled by default for Fedora Linux, so I would rather see a more sensitive default been taken even though the test runtime is fairly quickly on a small machine for now= . >=20 > [ 5.656916] debug_vm_pgtable: debug_vm_pgtable: Validating=20 > architecture page table helpers > [ 5.665661] debug_vm_pgtable: debug_vm_pgtable: Validated=20 > architecture page table helpers