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Sat, 15 Aug 2020 06:51:52 +0000 (UTC) Date: Sat, 15 Aug 2020 08:51:50 +0200 From: Andrew Jones To: Peng Liang Subject: Re: [RFC 2/9] target/arm: parse cpu feature related options Message-ID: <20200815065150.t54pb7jktueeft42@kamzik.brq.redhat.com> References: <20200813102657.2588720-1-liangpeng10@huawei.com> <20200813102657.2588720-3-liangpeng10@huawei.com> <20200813122113.3esshhhnolqpe6ok@kamzik.brq.redhat.com> <047ab475-8735-c684-b0cb-4f44d93b4a0b@huawei.com> MIME-Version: 1.0 In-Reply-To: <047ab475-8735-c684-b0cb-4f44d93b4a0b@huawei.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=drjones@redhat.com X-Mimecast-Spam-Score: 0.002 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Received-SPF: pass client-ip=205.139.110.120; envelope-from=drjones@redhat.com; helo=us-smtp-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/08/15 02:52:02 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -30 X-Spam_score: -3.1 X-Spam_bar: --- X-Spam_report: (-3.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=-0.01, RCVD_IN_MSPIKE_WL=-0.01, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action 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: peter.maydell@linaro.org, Zhanghailiang , mst@redhat.com, cohuck@redhat.com, qemu-devel@nongnu.org, xiexiangyou 00584000 , qemu-arm@nongnu.org, pbonzini@redhat.com, zhukeqian 00502301 Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Sat, Aug 15, 2020 at 10:19:12AM +0800, Peng Liang wrote: > On 8/13/2020 8:21 PM, Andrew Jones wrote: > > On Thu, Aug 13, 2020 at 06:26:50PM +0800, Peng Liang wrote: > >> The implementation of CPUClass::parse_features only supports CPU > >> features in "feature=value" format. However, libvirt maybe send us a > >> CPU feature string in "+feature/-feature" format. > > > > Why would libvirt do that? If we have a boolean feature, then I'd think > > libvirt should be capable of sending feature=on/off just as easily as a > > +/-feature. Indeed libvirt seems to do the right thing with all the > > CPU features we already have: pmu, sve*, ... > > > > Thanks, > > drew > > > > . > > > > Libvirt before d47db7b16dd5422c7e487c8c8ee5b181a2f9cd66 ("qemu: command: > Support new cpu feature argument syntax") will send +/-feature. Does QEMU > need to support it? If not, I'll remote it. No, we don't need to support pre-2016 libvirt, at least not for ARM CPU features, because libvirt didn't start querying QEMU for ARM CPU features until just last year. Thanks, drew