From mboxrd@z Thu Jan 1 00:00:00 1970 From: Catalin Marinas Date: Tue, 28 Jan 2020 17:47:09 +0000 Subject: Re: [PATCH V12] mm/debug: Add tests validating architecture page table helpers Message-Id: <20200128174709.GK655507@arrakis.emea.arm.com> List-Id: References: <1580174873-18117-1-git-send-email-anshuman.khandual@arm.com> <14882A91-17DE-4ABD-ABF2-08E7CCEDF660@lca.pw> In-Reply-To: <14882A91-17DE-4ABD-ABF2-08E7CCEDF660@lca.pw> MIME-Version: 1.0 Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: quoted-printable To: Qian Cai Cc: Mark Rutland , linux-ia64@vger.kernel.org, linux-sh@vger.kernel.org, Peter Zijlstra , James Hogan , Heiko Carstens , Michal Hocko , linux-mm@kvack.org, Paul Mackerras , sparclinux@vger.kernel.org, Ingo Molnar , linux-s390@vger.kernel.org, Jason Gunthorpe , Michael Ellerman , Vlastimil Babka , x86@kernel.org, Russell King - ARM Linux , Matthew Wilcox , Steven Price , Tetsuo Handa , linux-arm-kernel@lists.infradead.org, linux-snps-arc@lists.infradead.org, Kees Cook , Anshuman Khandual , Masahiro Yamada , Dan Williams , Mark Brown , "Kirill A . Shutemov" , Thomas Gleixner , Gerald Schaefer , Christophe Leroy , Sri Krishna chowdary , Dave Hansen , Greg Kroah-Hartman , Ard Biesheuvel , 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" On Mon, Jan 27, 2020 at 09:11:53PM -0500, Qian Cai wrote: > On Jan 27, 2020, at 8:28 PM, Anshuman Khandual wrote: > > This adds tests which will validate architecture page table helpers and > > other accessors in their compliance with expected generic MM semantics. > > This will help various architectures in validating changes to existing > > page table helpers or addition of new ones. [...] > What=E2=80=99s the value of this block of new code? It only supports x86 = and > arm64 which are supposed to be good now. Did those tests ever find any > regression or this is almost only useful for new architectures which > only happened once in a few years? 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. See for example this past discussion: https://lore.kernel.org/linux-mm/20190628102003.GA56463@arrakis.emea.arm.co= m/ These tests should act as the 'contract' between the generic mm code and the architecture port. Without clear semantics, some bugs may be a lot subtler than a boot failure. FTR, I fully support this patch (and I should get around to review it properly; thanks for the reminder ;)). --=20 Catalin