linux-kernel - Re: [PATCH v3 01/15] KVM: x86: Add a framework for enabling KVM-governed x86 features

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Message-ID: <6370c12ff6ec2c22ed5e1f1f37c1cf38a820a342.camel@intel.com>
Date:   Wed, 16 Aug 2023 01:36:05 +0000
From:   "Huang, Kai" <kai.huang@...el.com>
To:     "pbonzini@...hat.com" <pbonzini@...hat.com>,
        "Christopherson,, Sean" <seanjc@...gle.com>,
        "vkuznets@...hat.com" <vkuznets@...hat.com>
CC:     "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "Zeng, Guang" <guang.zeng@...el.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Yao, Yuan" <yuan.yao@...el.com>
Subject: Re: [PATCH v3 01/15] KVM: x86: Add a framework for enabling
 KVM-governed x86 features


>  
> +enum kvm_governed_features {
> +#define KVM_GOVERNED_FEATURE(x) KVM_GOVERNED_##x,
> +#include "governed_features.h"
> +	KVM_NR_GOVERNED_FEATURES
> +};
> +
> +static __always_inline int kvm_governed_feature_index(unsigned int x86_feature)
> +{
> +	switch (x86_feature) {
> +#define KVM_GOVERNED_FEATURE(x) case x: return KVM_GOVERNED_##x;
> +#include "governed_features.h"
> +	default:
> +		return -1;
> +	}
> +}
> +
> +static __always_inline bool kvm_is_governed_feature(unsigned int x86_feature)
> +{
> +	return kvm_governed_feature_index(x86_feature) >= 0;
> +}
> +
> +static __always_inline void kvm_governed_feature_set(struct kvm_vcpu *vcpu,
> +						     unsigned int x86_feature)
> +{
> +	BUILD_BUG_ON(!kvm_is_governed_feature(x86_feature));
> +
> +	__set_bit(kvm_governed_feature_index(x86_feature),
> +		  vcpu->arch.governed_features.enabled);
> +}
> +
> +static __always_inline void kvm_governed_feature_check_and_set(struct kvm_vcpu *vcpu,
> +							       unsigned int x86_feature)
> +{
> +	if (kvm_cpu_cap_has(x86_feature) && guest_cpuid_has(vcpu, x86_feature))
> +		kvm_governed_feature_set(vcpu, x86_feature);
> +}
> +
> +static __always_inline bool guest_can_use(struct kvm_vcpu *vcpu,
> +					  unsigned int x86_feature)
> +{
> +	BUILD_BUG_ON(!kvm_is_governed_feature(x86_feature));
> +
> +	return test_bit(kvm_governed_feature_index(x86_feature),
> +			vcpu->arch.governed_features.enabled);
> +}
> +
>  #endif
> diff --git a/arch/x86/kvm/governed_features.h b/arch/x86/kvm/governed_features.h
> new file mode 100644
> index 000000000000..40ce8e6608cd
> --- /dev/null
> +++ b/arch/x86/kvm/governed_features.h
> @@ -0,0 +1,9 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#if !defined(KVM_GOVERNED_FEATURE) || defined(KVM_GOVERNED_X86_FEATURE)
> +BUILD_BUG()
> +#endif
> +
> +#define KVM_GOVERNED_X86_FEATURE(x) KVM_GOVERNED_FEATURE(X86_FEATURE_##x)
> +
> +#undef KVM_GOVERNED_X86_FEATURE
> +#undef KVM_GOVERNED_FEATURE

Nit:

Do you want to move the very last

	#undef KVM_GOVERNED_FEATURE

out of "governed_features.h", but to the place(s) where the macro is defined?

Yes there will be multiple:

	#define KVM_GOVERNED_FEATURE(x)	...
	#include "governed_features.h"
	#undef KVM_GOVERNED_FEATURE

But this looks clearer to me.