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From: Paolo Bonzini <pbonzini@redhat.com>
Date: Wed, 22 May 2024 10:09:46 +0200
Message-ID: <CABgObfZL7dfczyeY=7Xh1YGqEZEzVsdMnM+D6yumFSNfLO7cfA@mail.gmail.com>
Subject: Re: [PATCH v2] KVM: SEV-ES: Don't intercept MSR_IA32_DEBUGCTLMSR for
 SEV-ES guests
To: Ravi Bangoria <ravi.bangoria@amd.com>
Cc: Sean Christopherson <seanjc@google.com>, thomas.lendacky@amd.com, tglx@linutronix.de, 
	mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, 
	hpa@zytor.com, michael.roth@amd.com, nikunj.dadhania@amd.com, 
	kvm@vger.kernel.org, linux-kernel@vger.kernel.org, santosh.shukla@amd.com
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On Wed, May 22, 2024 at 8:11=E2=80=AFAM Ravi Bangoria <ravi.bangoria@amd.co=
m> wrote:
> >>> LBR Virtualization overhead for guest entry + exit roundtrip is ~450 =
cycles* on
> >>
> >> Ouch.  Just to clearify, that's for LBR Stack Virtualization, correct?
> >
> > And they are all in the VMSA, triggered by LBR_CTL_ENABLE_MASK, for
> > non SEV-ES guests?
>
> Not sure I follow. LBR_CTL_ENABLE_MASK works same for all types of guests=
.
> Just that, it's mandatory for SEV-ES guests and optional for SVM and SEV
> guests.

I think you confirmed I mean: when you set LBR_CTL_ENABLE_MASK, you
get the 450 cycle penalty because the whole set of LBR Stack MSRs is
in the VMSA for both SVM/SEV guests (optional) and SEV-ES guests
(mandatory).

Paolo