linux-kernel - Re: [PATCH v3 13/18] x86/virt: KVM: Open code cpu_has_svm() into kvm_is_svm

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Message-ID: <7557efce6fa10cf9f3cdb807ed88ebc2b38a94b5.camel@intel.com>
Date:   Mon, 22 May 2023 23:44:00 +0000
From:   "Huang, Kai" <kai.huang@...el.com>
To:     "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "Christopherson,, Sean" <seanjc@...gle.com>
CC:     "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Gao, Chao" <chao.gao@...el.com>,
        "andrew.cooper3@...rix.com" <andrew.cooper3@...rix.com>
Subject: Re: [PATCH v3 13/18] x86/virt: KVM: Open code cpu_has_svm() into
 kvm_is_svm_supported()

On Fri, 2023-05-12 at 16:50 -0700, Sean Christopherson wrote:
> Fold the guts of cpu_has_svm() into kvm_is_svm_supported(), its sole
> remaining user.
> 
> No functional change intended.
> 
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>

The same to the reply to VMX patch:

Reviewed-by: Kai Huang <kai.huang@...el.com>

> ---
>  arch/x86/include/asm/virtext.h | 28 ----------------------------
>  arch/x86/kvm/svm/svm.c         | 11 ++++++++---
>  2 files changed, 8 insertions(+), 31 deletions(-)
> 
> diff --git a/arch/x86/include/asm/virtext.h b/arch/x86/include/asm/virtext.h
> index be50c414efe4..632575e257d8 100644
> --- a/arch/x86/include/asm/virtext.h
> +++ b/arch/x86/include/asm/virtext.h
> @@ -22,35 +22,7 @@
>  /*
>   * SVM functions:
>   */
> -
> -/** Check if the CPU has SVM support
> - *
> - * You can use the 'msg' arg to get a message describing the problem,
> - * if the function returns zero. Simply pass NULL if you are not interested
> - * on the messages; gcc should take care of not generating code for
> - * the messages on this case.
> - */
> -static inline int cpu_has_svm(const char **msg)
> -{
> -	if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD &&
> -	    boot_cpu_data.x86_vendor != X86_VENDOR_HYGON) {
> -		if (msg)
> -			*msg = "not amd or hygon";
> -		return 0;
> -	}
> -
> -	if (!boot_cpu_has(X86_FEATURE_SVM)) {
> -		if (msg)
> -			*msg = "svm not available";
> -		return 0;
> -	}
> -	return 1;
> -}
> -
> -
>  /** Disable SVM on the current CPU
> - *
> - * You should call this only if cpu_has_svm() returned true.
>   */

Nit: "double **" can be removed in the comment.

>  static inline void cpu_svm_disable(void)
>  {
> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> index 0f0d04900bf2..b347173b4e29 100644
> --- a/arch/x86/kvm/svm/svm.c
> +++ b/arch/x86/kvm/svm/svm.c
> @@ -526,11 +526,16 @@ static void svm_init_osvw(struct kvm_vcpu *vcpu)
>  static bool kvm_is_svm_supported(void)
>  {
>  	int cpu = raw_smp_processor_id();
> -	const char *msg;
>  	u64 vm_cr;
>  
> -	if (!cpu_has_svm(&msg)) {
> -		pr_err("SVM not supported by CPU %d, %s\n", cpu, msg);
> +	if (boot_cpu_data.x86_vendor != X86_VENDOR_AMD &&
> +	    boot_cpu_data.x86_vendor != X86_VENDOR_HYGON) {
> +		pr_err("CPU %d isn't AMD or Hygon\n", cpu);
> +		return false;
> +	}
> +
> +	if (!boot_cpu_has(X86_FEATURE_SVM)) {
> +		pr_err("SVM not supported by CPU %d\n", cpu);
>  		return false;
>  	}
>  
> -- 
> 2.40.1.606.ga4b1b128d6-goog
>