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From: Sean Christopherson <seanjc@google.com>
To: Maxim Levitsky <mlevitsk@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
	Vitaly Kuznetsov <vkuznets@redhat.com>,
	Wanpeng Li <wanpengli@tencent.com>,
	Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
	kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
	Xiaoyao Li <xiaoyao.li@intel.com>,
	Reiji Watanabe <reijiw@google.com>
Subject: Re: [PATCH 14/15] KVM: x86: Tie Intel and AMD behavior for MSR_TSC_AUX to guest CPU model
Date: Mon, 10 May 2021 16:50:23 +0000	[thread overview]
Message-ID: <YJlkT0kJ241gYgVw@google.com> (raw)
In-Reply-To: <7e75b44c0477a7fb87f83962e4ea2ed7337c37e5.camel@redhat.com>

On Mon, May 10, 2021, Maxim Levitsky wrote:
> On Tue, 2021-05-04 at 10:17 -0700, Sean Christopherson wrote:
> > diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> > index de921935e8de..6c7c6a303cc5 100644
> > --- a/arch/x86/kvm/svm/svm.c
> > +++ b/arch/x86/kvm/svm/svm.c
> > @@ -2663,12 +2663,6 @@ static int svm_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
> >  			msr_info->data |= (u64)svm->sysenter_esp_hi << 32;
> >  		break;
> >  	case MSR_TSC_AUX:
> > -		if (tsc_aux_uret_slot < 0)
> > -			return 1;
> > -		if (!msr_info->host_initiated &&
> Not related to this patch, but I do wonder why do we need
> to always allow writing this msr if done by the host,
> since if neither RDTSPC nor RDPID are supported, the guest
> won't be able to read this msr at all.

It's an ordering thing and not specific to MSR_TSC_AUX.  Exempting host userspace
from guest CPUID checks allows userspace to set MSR state, e.g. during migration,
before setting the guest CPUID model.

> > -		    !guest_cpuid_has(vcpu, X86_FEATURE_RDTSCP) &&
> > -		    !guest_cpuid_has(vcpu, X86_FEATURE_RDPID))
> > -			return 1;
> >  		msr_info->data = svm->tsc_aux;
> >  		break;
> >  	/*

  reply	other threads:[~2021-05-10 16:50 UTC|newest]

Thread overview: 68+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-04 17:17 [PATCH 00/15] KVM: x86: RDPID/RDTSCP fixes and uret MSR cleanups Sean Christopherson
2021-05-04 17:17 ` [PATCH 01/15] KVM: VMX: Do not adverise RDPID if ENABLE_RDTSCP control is unsupported Sean Christopherson
2021-05-04 17:37   ` Jim Mattson
2021-05-04 17:53     ` Jim Mattson
2021-05-04 18:14       ` Sean Christopherson
2021-05-05  3:04   ` Reiji Watanabe
2021-05-10  8:03   ` Maxim Levitsky
2021-05-04 17:17 ` [PATCH 02/15] KVM: x86: Emulate RDPID only if RDTSCP is supported Sean Christopherson
2021-05-04 17:50   ` Jim Mattson
2021-05-05  3:51   ` Reiji Watanabe
2021-05-05  8:01     ` Paolo Bonzini
2021-05-10  8:08   ` Maxim Levitsky
2021-05-10 17:20     ` Sean Christopherson
2021-05-11 12:32       ` Maxim Levitsky
2021-05-04 17:17 ` [PATCH 03/15] KVM: SVM: Inject #UD on RDTSCP when it should be disabled in the guest Sean Christopherson
2021-05-04 21:45   ` Jim Mattson
2021-05-04 21:53     ` Sean Christopherson
2021-05-04 21:56       ` Jim Mattson
2021-05-04 22:10         ` Sean Christopherson
2021-05-04 22:24           ` Jim Mattson
2021-05-04 21:57       ` Paolo Bonzini
2021-05-04 21:58         ` Jim Mattson
2021-05-10  8:08           ` Maxim Levitsky
2021-05-10 16:56             ` Sean Christopherson
2021-05-11 12:34               ` Maxim Levitsky
2021-05-18 10:59               ` Paolo Bonzini
2021-05-18 19:24                 ` Sean Christopherson
2021-05-05  4:26   ` Reiji Watanabe
2021-05-10  8:08   ` Maxim Levitsky
2021-05-04 17:17 ` [PATCH 04/15] KVM: x86: Move RDPID emulation intercept to its own enum Sean Christopherson
2021-05-04 23:24   ` Jim Mattson
2021-05-10  8:14   ` Maxim Levitsky
2021-05-04 17:17 ` [PATCH 05/15] KVM: VMX: Disable preemption when probing user return MSRs Sean Christopherson
2021-05-04 23:36   ` Jim Mattson
2021-05-10  8:18   ` Maxim Levitsky
2021-05-04 17:17 ` [PATCH 06/15] KVM: SVM: Probe and load MSR_TSC_AUX regardless of RDTSCP support in host Sean Christopherson
2021-05-10  8:20   ` Maxim Levitsky
2021-05-04 17:17 ` [PATCH 07/15] KVM: x86: Add support for RDPID without RDTSCP Sean Christopherson
2021-05-10  8:20   ` Maxim Levitsky
2021-05-04 17:17 ` [PATCH 08/15] KVM: VMX: Configure list of user return MSRs at module init Sean Christopherson
2021-05-10  8:23   ` Maxim Levitsky
2021-05-10 15:13     ` Sean Christopherson
2021-05-11 12:34       ` Maxim Levitsky
2021-05-11 20:10         ` Sean Christopherson
2021-05-04 17:17 ` [PATCH 09/15] KVM: VMX: Use flag to indicate "active" uret MSRs instead of sorting list Sean Christopherson
2021-05-08  3:31   ` Reiji Watanabe
2021-05-10 16:43     ` Sean Christopherson
2021-05-10 17:55       ` Reiji Watanabe
2021-05-10  8:25   ` Maxim Levitsky
2021-05-04 17:17 ` [PATCH 10/15] KVM: VMX: Use common x86's uret MSR list as the one true list Sean Christopherson
2021-05-10  8:25   ` Maxim Levitsky
2021-05-04 17:17 ` [PATCH 11/15] KVM: VMX: Disable loading of TSX_CTRL MSR the more conventional way Sean Christopherson
2021-05-05  8:49   ` Paolo Bonzini
2021-05-05 15:36     ` Sean Christopherson
2021-05-05 15:50       ` Paolo Bonzini
2021-05-10  8:26   ` Maxim Levitsky
2021-05-04 17:17 ` [PATCH 12/15] KVM: x86: Export the number of uret MSRs to vendor modules Sean Christopherson
2021-05-10  8:27   ` Maxim Levitsky
2021-05-04 17:17 ` [PATCH 13/15] KVM: x86: Move uret MSR slot management to common x86 Sean Christopherson
2021-05-10  8:28   ` Maxim Levitsky
2021-05-04 17:17 ` [PATCH 14/15] KVM: x86: Tie Intel and AMD behavior for MSR_TSC_AUX to guest CPU model Sean Christopherson
2021-05-10  8:29   ` Maxim Levitsky
2021-05-10 16:50     ` Sean Christopherson [this message]
2021-05-10 17:11       ` Jim Mattson
2021-05-11 12:34         ` Maxim Levitsky
2021-05-04 17:17 ` [PATCH 15/15] KVM: x86: Hide RDTSCP and RDPID if MSR_TSC_AUX probing failed Sean Christopherson
2021-05-10  8:29   ` Maxim Levitsky
2021-05-05  8:51 ` [PATCH 00/15] KVM: x86: RDPID/RDTSCP fixes and uret MSR cleanups Paolo Bonzini

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