linux-kernel - Re: [PATCH 3/5] x86/kvm: Convert some slow-path static_cpu_has() callers to boot_cpu

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Message-ID: <2f71cb35-46b2-9ed5-28b3-c6eb5e647b46@redhat.com>
Date:   Sun, 31 Mar 2019 16:20:11 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Borislav Petkov <bp@...en8.de>, LKML <linux-kernel@...r.kernel.org>
Cc:     Nadav Amit <nadav.amit@...il.com>,
        Andy Lutomirski <luto@...capital.net>,
        Peter Zijlstra <peterz@...radead.org>,
        "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        Radim Krčmář <rkrcmar@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>, x86@...nel.org
Subject: Re: [PATCH 3/5] x86/kvm: Convert some slow-path static_cpu_has()
 callers to boot_cpu_has()

On 30/03/19 12:20, Borislav Petkov wrote:
> @@ -2252,7 +2252,7 @@ static void svm_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
>  	for (i = 0; i < NR_HOST_SAVE_USER_MSRS; i++)
>  		rdmsrl(host_save_user_msrs[i], svm->host_user_msrs[i]);
>  
> -	if (static_cpu_has(X86_FEATURE_TSCRATEMSR)) {
> +	if (boot_cpu_has(X86_FEATURE_TSCRATEMSR)) {
>  		u64 tsc_ratio = vcpu->arch.tsc_scaling_ratio;
>  		if (tsc_ratio != __this_cpu_read(current_tsc_ratio)) {
>  			__this_cpu_write(current_tsc_ratio, tsc_ratio);
> @@ -2260,7 +2260,7 @@ static void svm_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
>  		}
>  	}
>  	/* This assumes that the kernel never uses MSR_TSC_AUX */
> -	if (static_cpu_has(X86_FEATURE_RDTSCP))
> +	if (boot_cpu_has(X86_FEATURE_RDTSCP))
>  		wrmsrl(MSR_TSC_AUX, svm->tsc_aux);
>  
>  	if (sd->current_vmcb != svm->vmcb) {
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index c73375e01ab8..0cb0d26564ca 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -6423,7 +6423,7 @@ static void vmx_vcpu_run(struct kvm_vcpu *vcpu)
>  	if (vcpu->guest_debug & KVM_GUESTDBG_SINGLESTEP)
>  		vmx_set_interrupt_shadow(vcpu, 0);
>  
> -	if (static_cpu_has(X86_FEATURE_PKU) &&
> +	if (boot_cpu_has(X86_FEATURE_PKU) &&
>  	    kvm_read_cr4_bits(vcpu, X86_CR4_PKE) &&
>  	    vcpu->arch.pkru != vmx->host_pkru)
>  		__write_pkru(vcpu->arch.pkru);
> @@ -6512,7 +6512,7 @@ static void vmx_vcpu_run(struct kvm_vcpu *vcpu)
>  	 * back on host, so it is safe to read guest PKRU from current
>  	 * XSAVE.
>  	 */
> -	if (static_cpu_has(X86_FEATURE_PKU) &&
> +	if (boot_cpu_has(X86_FEATURE_PKU) &&
>  	    kvm_read_cr4_bits(vcpu, X86_CR4_PKE)) {
>  		vcpu->arch.pkru = __read_pkru();

These are not slow path.

Paolo