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 BC8391E47D6; Fri, 13 Dec 2024 18:44:28 +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=1734115471; cv=none; b=l9ZaiXdSdj3UG/2GUaCfdVLGYagZB7d46JfwX/T99/yW1H8owYfmDXhkFP2u68bk890eq72xVnhzVsG3q1u8b7ZsuWhkau9GOADfcJyD0PeLOnAM/Ogwx8Jf+WHlnAQ+0v186qiAkDl5xBS7C+YDU7Xwb+RgIDQv2z2tAi75ryI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1734115471; c=relaxed/simple; bh=BGUhJ7s4wap9Trc0L03YqNCF5PervmrG+ZI0sPhI0Iw=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=F+X0eYELlhdyFGb7fLZDc5M0aXIAzalKTjQiA/f8NHaYWz+6mZhBHL/2swnZIzWSYqY+53KC8jBVjl353r9x7jE4U/2GSKdCMzGtWwxwd8a3kCSUzh9XbqY9MfFEIGpCy3ODInRo4Yi3fUBTvzbUxUuVuRoxL+ThHE0H8d9ZHNU= ARC-Authentication-Results:i=1; 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h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=ceDcUwUH7CqZWX44iL17eN8nw5RrcS4vDK62vWEYOx4MA2DGTpGbKXJUh5TlTeB+a aQFSWvCltZZOqLjr4cPPbMpByK3RrMy0phB+cHueogz+2DWCNXidHXmLUFkiMPrDeC mNnA4D2qexyIfyH5SX+2yXuodvc8D4R0DBxs53a43VjZN52WzOd596ng7UDaSB5Hxi ESgZjFH4J9n8hz9A7Pze2/DwlX0Wy52BRKPmCfeF12MXVoWxUtGLIQ0dnvMFf/BPje aNuBH6LBP78BMPK21B+oCL1L3T7KCV9diN9ddD1rFUUZSpPY2tr/KhNpom3uXzMITo Blawug5XjYX7w== Message-ID: <832e87d1-8349-47f8-b1dc-33768b534b10@zytor.com> Date: Fri, 13 Dec 2024 10:43:49 -0800 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 v3 17/27] KVM: x86: Mark CR4.FRED as not reserved when guest can use FRED To: Sean Christopherson Cc: Chao Gao , kvm@vger.kernel.org, linux-kernel@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 References: <20241001050110.3643764-1-xin@zytor.com> <20241001050110.3643764-18-xin@zytor.com> <3ec986fa-2bf0-4c78-b532-343ad19436b2@zytor.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 12/12/2024 11:05 AM, Sean Christopherson wrote: > On Thu, Dec 12, 2024, Xin Li wrote: >> On 10/24/2024 12:18 AM, Chao Gao wrote: >>>> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c >>>> index 03f42b218554..bfdd10773136 100644 >>>> --- a/arch/x86/kvm/vmx/vmx.c >>>> +++ b/arch/x86/kvm/vmx/vmx.c >>>> @@ -8009,6 +8009,10 @@ void vmx_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu) >>>> kvm_governed_feature_check_and_set(vcpu, X86_FEATURE_LAM); >>>> kvm_governed_feature_check_and_set(vcpu, X86_FEATURE_FRED); >>>> >>>> + /* Don't allow CR4.FRED=1 before all of FRED KVM support is in place. */ >>>> + if (!guest_can_use(vcpu, X86_FEATURE_FRED)) >>>> + vcpu->arch.cr4_guest_rsvd_bits |= X86_CR4_FRED; >>> >>> is this necessary? __kvm_is_valid_cr4() ensures that guests cannot set any bit >>> which isn't supported by the hardware. >>> >>> To account for hardware/KVM caps, I think the following changes will work. This >>> will fix all other bits besides X86_CR4_FRED. >> >> This seems a generic infra improvement, maybe it's better for you to >> send it as an individual patch to Sean and the KVM mailing list? > > Already ahead of y'all :-) (I think, I didn't look closely at this). > > https://lore.kernel.org/all/20241128013424.4096668-6-seanjc@google.com Ha, that is nice. Thank you!