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[71.184.117.43]) by smtp.gmail.com with ESMTPSA id f7sm13273329qtp.86.2020.01.28.11.07.10 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 28 Jan 2020 11:07:10 -0800 (PST) Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: quoted-printable From: Qian Cai Mime-Version: 1.0 (1.0) Subject: Re: [PATCH V12] mm/debug: Add tests validating architecture page table helpers Date: Tue, 28 Jan 2020 14:07:10 -0500 Message-Id: <69091BA4-18C4-4425-A5E2-31FBE4654AF9@lca.pw> References: <20200128174709.GK655507@arrakis.emea.arm.com> Cc: Anshuman Khandual , 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, Dave Hansen , 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, Ingo Molnar , Kees Cook , Masahiro Yamada , Mark Brown , "Kirill A . Shutemov" , Dan Williams , Vlastimil Babka , Christophe Leroy , Sri Krishna chowdary , Ard Biesheuvel , Greg Kroah-Hartman , 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" In-Reply-To: <20200128174709.GK655507@arrakis.emea.arm.com> To: Catalin Marinas X-Mailer: iPhone Mail (17C54) 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 Jan 28, 2020, at 12:47 PM, Catalin Marinas wr= ote: >=20 > The primary goal here is not finding regressions but having clearly > defined semantics of the page table accessors across architectures. x86 > and arm64 are a good starting point and other architectures will be > enabled as they are aligned to the same semantics. This still does not answer the fundamental question. If this test is simply i= nefficient to find bugs, who wants to spend time to use it regularly? If th= is is just one off test that may get running once in a few years (when intro= ducing a new arch), how does it justify the ongoing cost to maintain it? I do agree there could be a need to clearly define this thing but that belon= gs to documentation rather than testing purpose. It is confusing to mix this= with other config options which have somewhat a different purpose, it will t= hen be a waste of time for people who mistakenly enable this for regular aut= omatic testing and never found any bug from it.=