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h=Date:Subject:From:To:Cc:References:In-Reply-To:From; b=Y67HVPvl61EVkWatxnhOVeXKW63UykF8TU4cDEDQiKbePtlNSYbVPcCS7S1o7qRmW ki644wA0aln7/r+v87u68bpGmD+gJ/XFRJKJrP2lvuXu2IkbCYXV8wReZwNVkJATHP fv8LId0DEgqsrTbBisdaSSSwg/iEGOY7mz+Zw5EA5ttwpHkdZfOpefApYvzPdlNxU0 Kcerz93cj51dM7YRIk4YWSUMNUJ9bx2cTpxJKXy8J3kiE8gNmPf/uB48ITrEvtSZJX bgR0btyYoKr9XBOBoeWKFWPg8KpyBiiMmKXHJSWil8jM0W79ajOOIfFEkfQt9keelb vIPxGdpQNNGNg== Message-ID: <208429ae-d9c5-4b73-86ff-a9b31e68f7eb@zytor.com> Date: Fri, 27 Sep 2024 10:48:55 -0700 Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 07/25] KVM: VMX: Set intercept for FRED MSRs From: Xin Li To: Sean Christopherson 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 References: <20240207172646.3981-1-xin3.li@intel.com> <20240207172646.3981-8-xin3.li@intel.com> <496a337d-a20d-4122-93a9-1520779c6d2d@zytor.com> Content-Language: en-US Autocrypt: addr=xin@zytor.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit >>> When FRED is advertised to a guest, KVM should allow FRED SSP MSRs >>> accesses through disabling FRED SSP MSRs interception no matter whether >>> supervisor shadow stacks are enabled or not. >> >> 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.  KVM >> 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. >> >> And this means that yes, FRED virtualization needs to land after CET >> virtualization, >> otherwise managing the conflicts/dependencies will be a nightmare. >> 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? > > No argument.