linux-kernel - Re: [PATCH 01/15] KVM: VMX: Do not adverise RDPID if ENABLE

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Date:   Mon, 10 May 2021 11:03:10 +0300
From:   Maxim Levitsky <mlevitsk@...hat.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Cc:     Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, Xiaoyao Li <xiaoyao.li@...el.com>,
        Reiji Watanabe <reijiw@...gle.com>
Subject: Re: [PATCH 01/15] KVM: VMX: Do not adverise RDPID if ENABLE_RDTSCP
 control is unsupported

On Tue, 2021-05-04 at 10:17 -0700, Sean Christopherson wrote:
> Clear KVM's RDPID capability if the ENABLE_RDTSCP secondary exec control is
> unsupported.  Despite being enumerated in a separate CPUID flag, RDPID is
> bundled under the same VMCS control as RDTSCP and will #UD in VMX non-root
> if ENABLE_RDTSCP is not enabled.
> 
> Fixes: 41cd02c6f7f6 ("kvm: x86: Expose RDPID in KVM_GET_SUPPORTED_CPUID")
> Cc: stable@...r.kernel.org
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>
> ---
>  arch/x86/kvm/vmx/vmx.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index 10b610fc7bbc..82404ee2520e 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -7377,9 +7377,11 @@ static __init void vmx_set_cpu_caps(void)
>  	if (!cpu_has_vmx_xsaves())
>  		kvm_cpu_cap_clear(X86_FEATURE_XSAVES);
>  
> -	/* CPUID 0x80000001 */
> -	if (!cpu_has_vmx_rdtscp())
> +	/* CPUID 0x80000001 and 0x7 (RDPID) */
> +	if (!cpu_has_vmx_rdtscp()) {
>  		kvm_cpu_cap_clear(X86_FEATURE_RDTSCP);
> +		kvm_cpu_cap_clear(X86_FEATURE_RDPID);
> +	}
>  
>  	if (cpu_has_vmx_waitpkg())
>  		kvm_cpu_cap_check_and_set(X86_FEATURE_WAITPKG);

Reviewed-by: Maxim Levitsky <mlevitsk@...hat.com>

Best regards,
	Maxim Levitsky