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AJvYcCXghHJlU+or3yY+oPqRzkTpFnG32rUB3fUktnLV+n4UUqpqUjYMxjSTG5EeBUxM3Owo3oLEwx6vIi8=@vger.kernel.org X-Gm-Message-State: AOJu0YwF7QgXvp/Z54vMCgsWqWT1uqmf24vm1FAAnPJ7UtmlQ1RuHXXY r+TAqPSiWjNwC3xjpYO+xqNgPDoqoi2O2x/h0foAmANmZnbc7tlHuzFaXL0XOQEckuz8I1w1l1v BGg== X-Google-Smtp-Source: AGHT+IEC5NPofYVzP+Wzs2dXMq4oR3r2G7SGyWOX8ZxrYfWVkpnj7bsqqKMZB753besVJFViOSuQTmArTz8= X-Received: from zagreus.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5c37]) (user=seanjc job=sendgmr) by 2002:a25:2e4d:0:b0:e16:4d66:982e with SMTP id 3f1490d57ef6-e2604b436d5mr59541276.5.1727715391824; Mon, 30 Sep 2024 09:56:31 -0700 (PDT) Date: Mon, 30 Sep 2024 09:56:26 -0700 In-Reply-To: <208429ae-d9c5-4b73-86ff-a9b31e68f7eb@zytor.com> Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20240207172646.3981-1-xin3.li@intel.com> <20240207172646.3981-8-xin3.li@intel.com> <496a337d-a20d-4122-93a9-1520779c6d2d@zytor.com> <208429ae-d9c5-4b73-86ff-a9b31e68f7eb@zytor.com> Message-ID: Subject: Re: [PATCH v2 07/25] KVM: VMX: Set intercept for FRED MSRs From: Sean Christopherson To: Xin Li Cc: Chao Gao , Xin Li , linux-kernel@vger.kernel.org, kvm@vger.kernel.org, linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org, pbonzini@redhat.com, corbet@lwn.net, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, shuah@kernel.org, vkuznets@redhat.com, peterz@infradead.org, ravi.v.shankar@intel.com Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable On Fri, Sep 27, 2024, Xin Li wrote: > > > > When FRED is advertised to a guest, KVM should allow FRED SSP MSRs > > > > accesses through disabling FRED SSP MSRs interception no matter whe= ther > > > > supervisor shadow stacks are enabled or not. > > >=20 > > > KVM doesn't necessarily need to disabling MSR interception, e.g. if > > > the expectation > > > is that the guest will rarely/never access the MSRs when CET is > > > unsupported, then > > > we're likely better off going with a trap-and-emulate model.=C2=A0 KV= M > > > needs to emulate > > > RDMSR and WRMSR no matter what, e.g. in case the guest triggers a > > > WRMSR when KVM > > > is emulating, and so that userspace can get/set MSR values. > > >=20 > > > And this means that yes, FRED virtualization needs to land after CET > > > virtualization, > > > otherwise managing the conflicts/dependencies will be a nightmare. > > >=20 >=20 > I still plan to send another iteration of the FRED patch set for review, > however I haven't seen your x86 KVM changes land into Linus' tree, it > will happen soon, right? Yep, we squeaked into rc1, the pull request to Linus was delayed because of travel and conferences.