linux-kernel - Re: [PATCH v2 32/49] KVM: x86: Remove all direct usage of cpuid_entry2

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Date: Thu, 04 Jul 2024 21:52:02 -0400
From: Maxim Levitsky <mlevitsk@...hat.com>
To: Sean Christopherson <seanjc@...gle.com>, Paolo Bonzini
 <pbonzini@...hat.com>,  Vitaly Kuznetsov <vkuznets@...hat.com>
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org, Hou Wenlong
 <houwenlong.hwl@...group.com>, Kechen Lu <kechenl@...dia.com>, Oliver Upton
 <oliver.upton@...ux.dev>, Binbin Wu <binbin.wu@...ux.intel.com>, Yang
 Weijiang <weijiang.yang@...el.com>, Robert Hoo <robert.hoo.linux@...il.com>
Subject: Re: [PATCH v2 32/49] KVM: x86: Remove all direct usage of
 cpuid_entry2_find()

On Fri, 2024-05-17 at 10:39 -0700, Sean Christopherson wrote:
> Convert all use of cpuid_entry2_find() to kvm_find_cpuid_entry{,index}()
> now that cpuid_entry2_find() operates on the vCPU state, i.e. now that
> there is no need to use cpuid_entry2_find() directly in order to pass in
> non-vCPU state.
> 
> To help prevent unwanted usage of cpuid_entry2_find(), #undef
> KVM_CPUID_INDEX_NOT_SIGNIFICANT, i.e. force KVM to use
> kvm_find_cpuid_entry().
> 
> No functional change intended.
> 
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>
> ---
>  arch/x86/kvm/cpuid.c | 28 ++++++++++++++++------------
>  1 file changed, 16 insertions(+), 12 deletions(-)
> 
> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> index d7390ade1c29..699ce4261e9c 100644
> --- a/arch/x86/kvm/cpuid.c
> +++ b/arch/x86/kvm/cpuid.c
> @@ -189,6 +189,12 @@ struct kvm_cpuid_entry2 *kvm_find_cpuid_entry(struct kvm_vcpu *vcpu,
>  }
>  EXPORT_SYMBOL_GPL(kvm_find_cpuid_entry);
>  
> +/*
> + * cpuid_entry2_find() and KVM_CPUID_INDEX_NOT_SIGNIFICANT should never be used
> + * directly outside of kvm_find_cpuid_entry() and kvm_find_cpuid_entry_index().
> + */
> +#undef KVM_CPUID_INDEX_NOT_SIGNIFICANT
> +
>  static int kvm_check_cpuid(struct kvm_vcpu *vcpu)
>  {
>  	struct kvm_cpuid_entry2 *best;
> @@ -198,8 +204,7 @@ static int kvm_check_cpuid(struct kvm_vcpu *vcpu)
>  	 * The existing code assumes virtual address is 48-bit or 57-bit in the
>  	 * canonical address checks; exit if it is ever changed.
>  	 */
> -	best = cpuid_entry2_find(vcpu, 0x80000008,
> -				 KVM_CPUID_INDEX_NOT_SIGNIFICANT);
> +	best = kvm_find_cpuid_entry(vcpu, 0x80000008);
>  	if (best) {
>  		int vaddr_bits = (best->eax & 0xff00) >> 8;
>  
> @@ -211,7 +216,7 @@ static int kvm_check_cpuid(struct kvm_vcpu *vcpu)
>  	 * Exposing dynamic xfeatures to the guest requires additional
>  	 * enabling in the FPU, e.g. to expand the guest XSAVE state size.
>  	 */
> -	best = cpuid_entry2_find(vcpu, 0xd, 0);
> +	best = kvm_find_cpuid_entry_index(vcpu, 0xd, 0);
>  	if (!best)
>  		return 0;
>  
> @@ -254,7 +259,7 @@ static struct kvm_hypervisor_cpuid kvm_get_hypervisor_cpuid(struct kvm_vcpu *vcp
>  	u32 base;
>  
>  	for_each_possible_hypervisor_cpuid_base(base) {
> -		entry = cpuid_entry2_find(vcpu, base, KVM_CPUID_INDEX_NOT_SIGNIFICANT);
> +		entry = kvm_find_cpuid_entry(vcpu, base);
>  
>  		if (entry) {
>  			u32 signature[3];
> @@ -301,7 +306,7 @@ static u64 cpuid_get_supported_xcr0(struct kvm_vcpu *vcpu)
>  {
>  	struct kvm_cpuid_entry2 *best;
>  
> -	best = cpuid_entry2_find(vcpu, 0xd, 0);
> +	best = kvm_find_cpuid_entry_index(vcpu, 0xd, 0);
>  	if (!best)
>  		return 0;
>  
> @@ -312,7 +317,7 @@ void kvm_update_cpuid_runtime(struct kvm_vcpu *vcpu)
>  {
>  	struct kvm_cpuid_entry2 *best;
>  
> -	best = cpuid_entry2_find(vcpu, 1, KVM_CPUID_INDEX_NOT_SIGNIFICANT);
> +	best = kvm_find_cpuid_entry(vcpu, 1);
>  	if (best) {
>  		/* Update OSXSAVE bit */
>  		if (boot_cpu_has(X86_FEATURE_XSAVE))
> @@ -323,22 +328,22 @@ void kvm_update_cpuid_runtime(struct kvm_vcpu *vcpu)
>  			   vcpu->arch.apic_base & MSR_IA32_APICBASE_ENABLE);
>  	}
>  
> -	best = cpuid_entry2_find(vcpu, 7, 0);
> +	best = kvm_find_cpuid_entry_index(vcpu, 7, 0);
>  	if (best && boot_cpu_has(X86_FEATURE_PKU) && best->function == 0x7)
>  		cpuid_entry_change(best, X86_FEATURE_OSPKE,
>  				   kvm_is_cr4_bit_set(vcpu, X86_CR4_PKE));
>  
> -	best = cpuid_entry2_find(vcpu, 0xD, 0);
> +	best = kvm_find_cpuid_entry_index(vcpu, 0xD, 0);
>  	if (best)
>  		best->ebx = xstate_required_size(vcpu->arch.xcr0, false);
>  
> -	best = cpuid_entry2_find(vcpu, 0xD, 1);
> +	best = kvm_find_cpuid_entry_index(vcpu, 0xD, 1);
>  	if (best && (cpuid_entry_has(best, X86_FEATURE_XSAVES) ||
>  		     cpuid_entry_has(best, X86_FEATURE_XSAVEC)))
>  		best->ebx = xstate_required_size(vcpu->arch.xcr0, true);
>  
>  	if (!kvm_check_has_quirk(vcpu->kvm, KVM_X86_QUIRK_MISC_ENABLE_NO_MWAIT)) {
> -		best = cpuid_entry2_find(vcpu, 0x1, KVM_CPUID_INDEX_NOT_SIGNIFICANT);
> +		best = kvm_find_cpuid_entry(vcpu, 0x1);
>  		if (best)
>  			cpuid_entry_change(best, X86_FEATURE_MWAIT,
>  					   vcpu->arch.ia32_misc_enable_msr &
> @@ -352,8 +357,7 @@ static bool kvm_cpuid_has_hyperv(struct kvm_vcpu *vcpu)
>  #ifdef CONFIG_KVM_HYPERV
>  	struct kvm_cpuid_entry2 *entry;
>  
> -	entry = cpuid_entry2_find(vcpu, HYPERV_CPUID_INTERFACE,
> -				  KVM_CPUID_INDEX_NOT_SIGNIFICANT);
> +	entry = kvm_find_cpuid_entry(vcpu, HYPERV_CPUID_INTERFACE);
>  	return entry && entry->eax == HYPERV_CPUID_SIGNATURE_EAX;
>  #else
>  	return false;

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

Best regards,
	Maxim Levitsky