linux-kernel - Re: [PATCH v3 2/3] KVM: SEV-ES: Disallow SEV-ES guests when X86_FEATURE

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Date: Tue, 28 May 2024 18:33:05 +0200
From: Paolo Bonzini <pbonzini@...hat.com>
To: Ravi Bangoria <ravi.bangoria@....com>, seanjc@...gle.com,
 nikunj.dadhania@....com
Cc: thomas.lendacky@....com, tglx@...utronix.de, mingo@...hat.com,
 bp@...en8.de, dave.hansen@...ux.intel.com, x86@...nel.org, hpa@...or.com,
 michael.roth@....com, pankaj.gupta@....com, kvm@...r.kernel.org,
 linux-kernel@...r.kernel.org, santosh.shukla@....com
Subject: Re: [PATCH v3 2/3] KVM: SEV-ES: Disallow SEV-ES guests when
 X86_FEATURE_LBRV is absent

On 5/23/24 14:18, Ravi Bangoria wrote:
> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> index 489b0183f37d..dcb5eb00a4f5 100644
> --- a/arch/x86/kvm/svm/svm.c
> +++ b/arch/x86/kvm/svm/svm.c
> @@ -5308,11 +5308,17 @@ static __init int svm_hardware_setup(void)
>   
>   	nrips = nrips && boot_cpu_has(X86_FEATURE_NRIPS);
>   
> +	if (lbrv) {
> +		if (!boot_cpu_has(X86_FEATURE_LBRV))
> +			lbrv = false;
> +		else
> +			pr_info("LBR virtualization supported\n");
> +	}
>   	/*
>   	 * Note, SEV setup consumes npt_enabled and enable_mmio_caching (which
>   	 * may be modified by svm_adjust_mmio_mask()), as well as nrips.
>   	 */

Since it consumes nrips, just make lbrv non-static:

/* enable/disable Next RIP Save */
int nrips = true;
module_param(nrips, int, 0444);

Paolo