linux-kernel - Re: [PATCH v2 3/4] KVM: SVM: Don't advertise Bus Lock Detect to guest if SVM support is missing

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Message-ID: <CALMp9eTan+OGKbRbZup1SVnHN0T0T0Ed_CVmooev446QDejqPQ@mail.gmail.com>
Date: Fri, 12 Jul 2024 16:33:03 -0700
From: Jim Mattson <jmattson@...gle.com>
To: Ravi Bangoria <ravi.bangoria@....com>
Cc: tglx@...utronix.de, mingo@...hat.com, bp@...en8.de, 
	dave.hansen@...ux.intel.com, seanjc@...gle.com, pbonzini@...hat.com, 
	thomas.lendacky@....com, hpa@...or.com, rmk+kernel@...linux.org.uk, 
	peterz@...radead.org, james.morse@....com, lukas.bulwahn@...il.com, 
	arjan@...ux.intel.com, j.granados@...sung.com, sibs@...natelecom.cn, 
	nik.borisov@...e.com, michael.roth@....com, nikunj.dadhania@....com, 
	babu.moger@....com, x86@...nel.org, kvm@...r.kernel.org, 
	linux-kernel@...r.kernel.org, santosh.shukla@....com, ananth.narayan@....com, 
	sandipan.das@....com, manali.shukla@....com
Subject: Re: [PATCH v2 3/4] KVM: SVM: Don't advertise Bus Lock Detect to guest
 if SVM support is missing

On Fri, Jul 12, 2024 at 2:41 AM Ravi Bangoria <ravi.bangoria@....com> wrote:
>
> If host supports Bus Lock Detect, KVM advertises it to guests even if
> SVM support is absent. Additionally, guest wouldn't be able to use it
> despite guest CPUID bit being set. Fix it by unconditionally clearing
> the feature bit in KVM cpu capability.
>
> Reported-by: Jim Mattson <jmattson@...gle.com>
> Closes: https://lore.kernel.org/r/CALMp9eRet6+v8Y1Q-i6mqPm4hUow_kJNhmVHfOV8tMfuSS=tVg@mail.gmail.com
> Fixes: 76ea438b4afc ("KVM: X86: Expose bus lock debug exception to guest")
> Cc: stable@...r.kernel.org
> Signed-off-by: Ravi Bangoria <ravi.bangoria@....com>
Reviewed-by: Jim Mattson <jmattson@...gle.com>