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Fri, 27 Nov 2020 18:16:35 +0000 MIME-Version: 1.0 Date: Fri, 27 Nov 2020 18:16:35 +0000 From: Marc Zyngier To: Quentin Perret Subject: Re: [PATCH v4 03/14] KVM: arm64: Kill 32-bit vCPUs on systems with mismatched EL0 support In-Reply-To: <20201127172434.GA984327@google.com> References: <20201124155039.13804-1-will@kernel.org> <20201124155039.13804-4-will@kernel.org> <9bd06b193e7fb859a1207bb1302b7597@kernel.org> <20201127115304.GB20564@willie-the-truck> <583c4074bbd4cf8b8085037745a5d1c0@kernel.org> <20201127172434.GA984327@google.com> User-Agent: Roundcube Webmail/1.4.9 Message-ID: <9de8639549040b4478b312503fd5a23f@kernel.org> X-Sender: maz@kernel.org X-SA-Exim-Connect-IP: 51.254.78.96 X-SA-Exim-Rcpt-To: qperret@google.com, will@kernel.org, linux-arm-kernel@lists.infradead.org, linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org, catalin.marinas@arm.com, gregkh@linuxfoundation.org, peterz@infradead.org, morten.rasmussen@arm.com, qais.yousef@arm.com, surenb@google.com, tj@kernel.org, lizefan@huawei.com, hannes@cmpxchg.org, mingo@redhat.com, juri.lelli@redhat.com, vincent.guittot@linaro.org, kernel-team@android.com X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20201127_131639_203873_7C3CA091 X-CRM114-Status: GOOD ( 13.77 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-arch@vger.kernel.org, Juri Lelli , kernel-team@android.com, Vincent Guittot , Ingo Molnar , Peter Zijlstra , Catalin Marinas , Johannes Weiner , linux-kernel@vger.kernel.org, Qais Yousef , Suren Baghdasaryan , Li Zefan , Greg Kroah-Hartman , Tejun Heo , Will Deacon , Morten Rasmussen , linux-arm-kernel@lists.infradead.org Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 2020-11-27 17:24, Quentin Perret wrote: > On Friday 27 Nov 2020 at 17:14:11 (+0000), Marc Zyngier wrote: [...] >> Yeah, the sanitized read feels better, if only because that is >> what we are going to read in all the valid cases, unfortunately. >> read_sanitised_ftr_reg() is sadly not designed to be called on >> a fast path, meaning that 32bit guests will do a bsearch() on >> the ID-regs every time they exit... >> >> I guess we will have to evaluate how much we loose with this. > > Could we use the trick we have for arm64_ftr_reg_ctrel0 to speed this > up? Maybe. I want to first verify whether this has any measurable impact. Another possibility would be to cache the last read_sanitised_ftr_reg() access, just to see if that helps. There shouldn't be that many code paths hammering it. Thanks, M. -- Jazz is not dead. It just smells funny... _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel