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 733B32BEC4A; Wed, 27 Aug 2025 22:43:30 +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=1756334613; cv=none; b=hrXxvq/C9fbxFznw8A71fdAga1lVrCs9ZLcaXQ6p3hwgCehlFP1M9mtrs7WDzkjliQh+T1rHYjmpC+hk56CVsWH6TRTLCwbVwS84XNemD8JoybnzD7p/Tr439iblrr4bkRb+/zHrgGTfxkrcQz/3TIkYYuzdzG84MzuJUaF8piU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1756334613; c=relaxed/simple; bh=M5wBJ5H/Lnxt0nRISLvUE9r5Wrj+wr3mKLmfL7JYRsw=; h=Message-ID:Date:MIME-Version:Subject:From:To:Cc:References: In-Reply-To:Content-Type; b=iYqEIYYI8PYfuShaO5VzZB8ZNcnuffdHJG/iK1l0t/LbcvQgkyxVlOKRnyJbr2jO7nWzcX96Xlp58I0We6TvJmmk9JVFXdTnJFaRgiKxLgzl6TUAmM9F+tCH2ygE6bZlK0jc7ybYFmRLtlP6eScbHN6Gm03H9T0DpKn8X6iiX3M= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=zytor.com; spf=pass smtp.mailfrom=zytor.com; dkim=pass (2048-bit key) header.d=zytor.com header.i=@zytor.com header.b=MREP9Mkt; arc=none smtp.client-ip=198.137.202.136 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=zytor.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=zytor.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=zytor.com header.i=@zytor.com header.b="MREP9Mkt" Received: from [192.168.7.202] ([71.202.166.45]) (authenticated bits=0) by mail.zytor.com (8.18.1/8.17.1) with ESMTPSA id 57RMh0x81916010 (version=TLSv1.3 cipher=TLS_AES_128_GCM_SHA256 bits=128 verify=NO); Wed, 27 Aug 2025 15:43:01 -0700 DKIM-Filter: OpenDKIM Filter v2.11.0 mail.zytor.com 57RMh0x81916010 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=zytor.com; s=2025082201; t=1756334582; bh=GlD3nUD4hvTwMTAZekHH9XvHUFOJHjy73HK/6D0khgk=; h=Date:Subject:From:To:Cc:References:In-Reply-To:From; b=MREP9MktjbZSfaJ2jbw6MizbnXzyx0wEHKk7LXZuQKT6t4asZDmO/RizqmXZtqDBa QvMoAI1/em3pzOzRchmEu9OF3+eQHRz3v/mtUr3yjYQ4919wzBC1/lJLLKAVBq1wGe DO+b56aJeH54/G7a/AaSp7lpR/uj3JJg/nxxxRC1AU75AkjVhpeQd+CKi2q03sjFK1 HZiBUmFQTVIosZTP2y1+ZlH4oPyRRTrlPCno+HmYMpTLiJT1ugtxWdWhqKxN53H1Eh w2aNTL9CQksujqdIXXXoFgF2vrthxelUBu+leY9CZ5CjY0F9uDa3nJ7U676N5ZXudR +wbMZf2Rujlnw== Message-ID: <77076b24-c503-40e8-9459-ede808074f0f@zytor.com> Date: Wed, 27 Aug 2025 15:43:00 -0700 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v6 06/20] KVM: VMX: Set FRED MSR intercepts From: Xin Li To: Sean Christopherson Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, linux-doc@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, luto@kernel.org, peterz@infradead.org, andrew.cooper3@citrix.com, chao.gao@intel.com, hch@infradead.org References: <20250821223630.984383-1-xin@zytor.com> <20250821223630.984383-7-xin@zytor.com> <2dd8c323-7654-4a28-86f1-d743b70d10b1@zytor.com> <5b1c5f80-bbe1-4294-8ede-5e097e8feda1@zytor.com> Content-Language: en-US Autocrypt: addr=xin@zytor.com; keydata= xsDNBGUPz1cBDACS/9yOJGojBFPxFt0OfTWuMl0uSgpwk37uRrFPTTLw4BaxhlFL0bjs6q+0 2OfG34R+a0ZCuj5c9vggUMoOLdDyA7yPVAJU0OX6lqpg6z/kyQg3t4jvajG6aCgwSDx5Kzg5 Rj3AXl8k2wb0jdqRB4RvaOPFiHNGgXCs5Pkux/qr0laeFIpzMKMootGa4kfURgPhRzUaM1vy bsMsL8vpJtGUmitrSqe5dVNBH00whLtPFM7IbzKURPUOkRRiusFAsw0a1ztCgoFczq6VfAVu raTye0L/VXwZd+aGi401V2tLsAHxxckRi9p3mc0jExPc60joK+aZPy6amwSCy5kAJ/AboYtY VmKIGKx1yx8POy6m+1lZ8C0q9b8eJ8kWPAR78PgT37FQWKYS1uAroG2wLdK7FiIEpPhCD+zH wlslo2ETbdKjrLIPNehQCOWrT32k8vFNEMLP5G/mmjfNj5sEf3IOKgMTMVl9AFjsINLHcxEQ 6T8nGbX/n3msP6A36FDfdSEAEQEAAc0WWGluIExpIDx4aW5Aenl0b3IuY29tPsLBDQQTAQgA NxYhBIUq/WFSDTiOvUIqv2u9DlcdrjdRBQJlD89XBQkFo5qAAhsDBAsJCAcFFQgJCgsFFgID AQAACgkQa70OVx2uN1HUpgv/cM2fsFCQodLArMTX5nt9yqAWgA5t1srri6EgS8W3F+3Kitge tYTBKu6j5BXuXaX3vyfCm+zajDJN77JHuYnpcKKr13VcZi1Swv6Jx1u0II8DOmoDYLb1Q2ZW v83W55fOWJ2g72x/UjVJBQ0sVjAngazU3ckc0TeNQlkcpSVGa/qBIHLfZraWtdrNAQT4A1fa sWGuJrChBFhtKbYXbUCu9AoYmmbQnsx2EWoJy3h7OjtfFapJbPZql+no5AJ3Mk9eE5oWyLH+ QWqtOeJM7kKvn/dBudokFSNhDUw06e7EoVPSJyUIMbYtUO7g2+Atu44G/EPP0yV0J4lRO6EA wYRXff7+I1jIWEHpj5EFVYO6SmBg7zF2illHEW31JAPtdDLDHYcZDfS41caEKOQIPsdzQkaQ oW2hchcjcMPAfyhhRzUpVHLPxLCetP8vrVhTvnaZUo0xaVYb3+wjP+D5j/3+hwblu2agPsaE vgVbZ8Fx3TUxUPCAdr/p73DGg57oHjgezsDNBGUPz1gBDAD4Mg7hMFRQqlzotcNSxatlAQNL MadLfUTFz8wUUa21LPLrHBkUwm8RujehJrzcVbPYwPXIO0uyL/F///CogMNx7Iwo6by43KOy g89wVFhyy237EY76j1lVfLzcMYmjBoTH95fJC/lVb5Whxil6KjSN/R/y3jfG1dPXfwAuZ/4N cMoOslWkfZKJeEut5aZTRepKKF54T5r49H9F7OFLyxrC/uI9UDttWqMxcWyCkHh0v1Di8176 jjYRNTrGEfYfGxSp+3jYL3PoNceIMkqM9haXjjGl0W1B4BidK1LVYBNov0rTEzyr0a1riUrp Qk+6z/LHxCM9lFFXnqH7KWeToTOPQebD2B/Ah5CZlft41i8L6LOF/LCuDBuYlu/fI2nuCc8d m4wwtkou1Y/kIwbEsE/6RQwRXUZhzO6llfoN96Fczr/RwvPIK5SVMixqWq4QGFAyK0m/1ap4 bhIRrdCLVQcgU4glo17vqfEaRcTW5SgX+pGs4KIPPBE5J/ABD6pBnUUAEQEAAcLA/AQYAQgA JhYhBIUq/WFSDTiOvUIqv2u9DlcdrjdRBQJlD89ZBQkFo5qAAhsMAAoJEGu9DlcdrjdR4C0L /RcjolEjoZW8VsyxWtXazQPnaRvzZ4vhmGOsCPr2BPtMlSwDzTlri8BBG1/3t/DNK4JLuwEj OAIE3fkkm+UG4Kjud6aNeraDI52DRVCSx6xff3bjmJsJJMb12mWglN6LjdF6K+PE+OTJUh2F dOhslN5C2kgl0dvUuevwMgQF3IljLmi/6APKYJHjkJpu1E6luZec/lRbetHuNFtbh3xgFIJx 2RpgVDP4xB3f8r0I+y6ua+p7fgOjDLyoFjubRGed0Be45JJQEn7A3CSb6Xu7NYobnxfkwAGZ Q81a2XtvNS7Aj6NWVoOQB5KbM4yosO5+Me1V1SkX2jlnn26JPEvbV3KRFcwV5RnDxm4OQTSk PYbAkjBbm+tuJ/Sm+5Yp5T/BnKz21FoCS8uvTiziHj2H7Cuekn6F8EYhegONm+RVg3vikOpn gao85i4HwQTK9/D1wgJIQkdwWXVMZ6q/OALaBp82vQ2U9sjTyFXgDjglgh00VRAHP7u1Rcu4 l75w1xInsg== In-Reply-To: <5b1c5f80-bbe1-4294-8ede-5e097e8feda1@zytor.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 8/27/2025 3:24 PM, Xin Li wrote: > On 8/26/2025 3:17 PM, Sean Christopherson wrote: >>> +        if (!kvm_cpu_cap_has(X86_FEATURE_SHSTK)) >>> +            wrmsrns(MSR_IA32_FRED_SSP0, vmx->msr_guest_fred_ssp0); >> FWIW, if we can't get an SDM change, don't bother with RDMSR/WRMSRNS, just >> configure KVM to intercept accesses.  Then in kvm_set_msr_common(), pivot on >> X86_FEATURE_SHSTK, e.g. > > > Intercepting is a solid approach: it ensures the guest value is fully > virtual and does not affect the hardware FRED SSP0 MSR.  Of course the code > is also simplified. > > >> >>     case MSR_IA32_U_CET: >>     case MSR_IA32_PL0_SSP ... MSR_IA32_PL3_SSP: >>         if (!kvm_cpu_cap_has(X86_FEATURE_SHSTK)) { >>             WARN_ON_ONCE(msr != MSR_IA32_FRED_SSP0); >>             vcpu->arch.fred_rsp0_fallback = data; Putting fred_rsp0_fallback in struct kvm_vcpu_arch reminds me one thing: We know AMD will do FRED and follow the FRED spec for bare metal, but regarding virtualization of FRED, I have no idea how it will be done on AMD, so I keep the KVM FRED code in VMX files, e.g., msr_guest_fred_rsp0 is defined in struct vcpu_vmx, and saved/restored in vmx.c. It is a future task to make common KVM FRED code for Intel and AMD.