From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail.zytor.com (terminus.zytor.com [198.137.202.136]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 56CC71D5AD5; Wed, 25 Sep 2024 22:14:07 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.137.202.136 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1727302449; cv=none; b=ie0rw/CDtOjEWQZndfPsZRt2ZGXI5BkQb330fRJMBqdnAezQtJ7kSR3wCCiMKzaRP4LiC2KnxYrrOPMVQq3wQq70pP2JsxZfSo3WurkMAbfZ8ZbCqw+U0QNR8i6q0YPTY8wnLiVsnpUU7oDcFZh+puVfhRz33OWYInKR2JZcPKQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1727302449; c=relaxed/simple; bh=IF41UnyDrl53g+NYIdXxL2UzRFa3oU7Z0qkEPuNrQUI=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=M4HunHpjgu0nlFvvx8LzC5V3DKIkLwcw/YDHhpnn9mbxakp6S4slO3/xL3YhKYHhXMimCSfSbXFei3VQotQXSTEdSO+Cbgy1Hn5wSfSvhDrsKtKbtXRzUJxbX/0dtBkKNOr1r2SfRQqQKR3rumGu31ImlLlJHny363CLW5rrPoQ= ARC-Authentication-Results:i=1; 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h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=Qqkv7BK45SoUUrLPuZ/VMtYlhuHPSof+LhTQxp8X/Gvmn+rODfXnAU3V3BVtyAnI0 7ydgtN+JW3vBfCJ9cAOv6BDDDcfTDKBf+d22xo7htig+8t8ztVE/GO22Z4TB5ederi g2I4ENVx51wLUbicAj4LER+Y+36gdqblDdv1SNKzJaScfqY5x9aysxBn3dgYZIWYzE jSgPy1Mnodt5JfhK7ggCPgEQfYTsvv0Vo0YTWbqRGYbE+gCD+irBBlyagDtek6wpd1 ZeseV3vbk1FZu5vtYVv9WJQr9mmCfX0HIvLSnM/Fe2ivl98Do5wblJvmSBV3c1q/jh a+4RC7gAe27Aw== Message-ID: <496a337d-a20d-4122-93a9-1520779c6d2d@zytor.com> Date: Wed, 25 Sep 2024 15:13:22 -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 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> Content-Language: en-US From: Xin Li Autocrypt: addr=xin@zytor.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 9/25/2024 7:12 AM, Sean Christopherson wrote: > On Wed, Sep 18, 2024, Xin Li wrote: >> You mean the following patch set, right? > > Yep, and presumably the KVM support as well: I assume it's close to KVM upstreaming criteria :) > > https://lore.kernel.org/all/20240219074733.122080-1-weijiang.yang@intel.com > >> https://lore.kernel.org/kvm/20240531090331.13713-1-weijiang.yang@intel.com/ > ... >> >> 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. > No argument. Thanks! Xin