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[97.126.123.70]) by smtp.gmail.com with ESMTPSA id d14sm92154pjz.12.2020.03.02.08.24.07 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 02 Mar 2020 08:24:07 -0800 (PST) Subject: Re: [PATCH 2/8] target/arm: Optimize cpu_mmu_index To: Peter Maydell References: <20200225031222.15434-1-richard.henderson@linaro.org> <20200225031414.15649-1-richard.henderson@linaro.org> From: Richard Henderson Message-ID: <4674d1cc-e6f1-fcf1-3fc7-6d275bb5b477@linaro.org> Date: Mon, 2 Mar 2020 08:24:05 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.4.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 2607:f8b0:4864:20::1043 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: qemu-arm , QEMU Developers Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 3/2/20 4:03 AM, Peter Maydell wrote: > On Tue, 25 Feb 2020 at 03:14, Richard Henderson > wrote: >> >> We now cache the core mmu_idx in env->hflags. Rather than recompute >> from scratch, extract the field. All of the uses of cpu_mmu_index >> within target/arm are within helpers where env->hflags is stable. > > Do you mean "within helpers, and env->hflags is always stable in > a helper", or "within helpers, and env->hflags is stable for the > particular set of helpers where we use cpu_mmu_index, though it might > not be in other helpers" ? The former. With the caveat that it's pretty clear when a helper is doing things that make it the exception to that rule. E.g. helper_exception_return, which itself invokes rebuild_hflags. r~