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[172.10.233.147]) by smtp.gmail.com with ESMTPSA id g13sm26718otl.60.2021.01.26.15.28.43 (version=TLS1 cipher=ECDHE-ECDSA-AES128-SHA bits=128/128); Tue, 26 Jan 2021 15:28:44 -0800 (PST) Date: Tue, 26 Jan 2021 15:28:22 -0800 (PST) From: Hugh Dickins X-X-Sender: hugh@eggly.anvils To: Will Deacon cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, Catalin Marinas , Jan Kara , Minchan Kim , Andrew Morton , "Kirill A . Shutemov" , Linus Torvalds , Vinayak Menon , Hugh Dickins , Nick Desaulniers , kernel-team@android.com Subject: Re: [PATCH v4 0/8] Create 'old' ptes for faultaround mappings on arm64 with hardware access flag In-Reply-To: <20210126230851.GE30941@willie-the-truck> Message-ID: References: <20210120173612.20913-1-will@kernel.org> <20210126230851.GE30941@willie-the-truck> User-Agent: Alpine 2.11 (LSU 23 2013-08-11) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 26 Jan 2021, Will Deacon wrote: > On Wed, Jan 20, 2021 at 05:36:04PM +0000, Will Deacon wrote: > > Hi all, > > > > This is version four of the patches I previously posted here: > > > > v1: https://lore.kernel.org/r/20201209163950.8494-1-will@kernel.org > > v2: https://lore.kernel.org/r/20210108171517.5290-1-will@kernel.org > > v3: https://lore.kernel.org/r/20210114175934.13070-1-will@kernel.org > > > > The patches allow architectures to opt-in at runtime for faultaround > > mappings to be created as 'old' instead of 'young'. Although there have > > been previous attempts at this, they failed either because the decision > > was deferred to userspace [1] or because it was done unconditionally and > > shown to regress benchmarks for particular architectures [2]. > > > > The big change since v3 is that the immutable fields of 'struct vm_fault' > > now live in a 'const' anonymous struct. Although Clang will silently > > accept modifications to these fields [3], GCC emits an error. The > > resulting diffstat is _considerably_ more manageable with this approach. > > The only changes I have pending against this series are cosmetic (commit > logs). Can I go ahead and queue this in the arm64 tree so that it can sit > in linux-next for a bit? (positive or negative feedback appreciated!). That would be fine by me: I ran v3 on rc3, then the nicer smaller v4 on rc4, and saw no problems when running either of them (x86_64 only). Hugh