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Tue, 05 Mar 2024 05:25:10 -0800 (PST) X-Google-Smtp-Source: AGHT+IE3q9RiTK82INQT11px/g7VIRLAj70Wti28vSUgsmf6eyI91e6IAGPZF2EIGY65Wv97eXWB3w== X-Received: by 2002:a05:600c:4504:b0:412:b42c:8ff1 with SMTP id t4-20020a05600c450400b00412b42c8ff1mr10684160wmo.21.1709645110217; Tue, 05 Mar 2024 05:25:10 -0800 (PST) Received: from localhost ([2a01:e0a:a9a:c460:2827:8723:3c60:c84a]) by smtp.gmail.com with ESMTPSA id t16-20020a05600c451000b00412e13bb942sm7280397wmo.19.2024.03.05.05.25.09 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 05 Mar 2024 05:25:09 -0800 (PST) Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 Date: Tue, 05 Mar 2024 14:25:09 +0100 Message-Id: From: "Anthony Harivel" To: =?utf-8?b?RGFuaWVsIFAuIEJlcnJhbmfDqQ==?= Cc: , , , Subject: Re: [PATCH v3 3/3] Add support for RAPL MSRs in KVM/Qemu X-Mailer: aerc/0.15.2-111-g39195000e213 References: <20240125072214.318382-1-aharivel@redhat.com> <20240125072214.318382-4-aharivel@redhat.com> In-Reply-To: Received-SPF: pass client-ip=170.10.129.124; envelope-from=aharivel@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -26 X-Spam_score: -2.7 X-Spam_bar: -- X-Spam_report: (-2.7 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.568, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Daniel P. Berrang=C3=A9, Mar 04, 2024 at 15:48: > On Mon, Mar 04, 2024 at 03:41:02PM +0100, Anthony Harivel wrote: > >=20 > > Hi Daniel, > >=20 > > > > + if (s->msr_energy.enable =3D=3D true) { > > > > > > This looks to be where we need to check that both the host CPU > > > vendor is intel, and the guest CPU vendor is intel, and that > > > the host CPU has the RAPL feature we're using. > > > > Checking for the host cpu and RAPL enable is fine and done.=20 > >=20 > > But checking for guest CPU is confusing me.=20 > > The RAPL feature is enable only with KVM enable.=20 > > This means "-cpu" can only be "host" or its derivative that essentially= =20 > > copy the host CPU definition, no? > > KVM can use any named CPU. > > > That means if we are already checking the host cpu we don't need to do= =20 > > anything for the guest, do we ? > > When I first wrote this I though it would be as simple as checknig a > CPUID feature flag. That appears to not be the case, however, as Linux > is just checking for various CPU models directly. With that in mind > perhaps we should just check of the guest CPU model vendor > =3D=3D CPUID_VENDOR_INTEL and leave it at that. > > eg, create an error if running an AMD CPU such as $QEMU -cpu EPYC The idea looks good to me. Now the hiccups of this solution is that=20 I cannot find a way to reach CPUArchState at this level of code (i.e=20 kvm_arch_init() ) with only the MachineState or the KVMState.=20 I can only reach the topology with x86_possible_cpu_arch_ids(). CPUArchState struct is holding the cpuid_vendor variables where we can=20 use IS_INTEL_CPU() for checking. Maybe you know the trick that I miss ?=20 Regards, Anthony > > With regards, > Daniel > --=20 > |: https://berrange.com -o- https://www.flickr.com/photos/dberran= ge :| > |: https://libvirt.org -o- https://fstop138.berrange.c= om :| > |: https://entangle-photo.org -o- https://www.instagram.com/dberran= ge :|