Re: [PATCH v3 4/8] KVM: X86: Split kvm_update_cpuid()

[Xiaoyao Li <xiaoyao.li@xxxxxxxxx>]

On 7/8/2020 8:06 PM, Paolo Bonzini wrote:
> On 08/07/20 08:50, Xiaoyao Li wrote:
> > Split the part of updating vcpu model out of kvm_update_cpuid(), and put
> > it into a new kvm_update_vcpu_model(). So it's more clear that
> > kvm_update_cpuid() is to update guest CPUID settings, while
> > kvm_update_vcpu_model() is to update vcpu model (settings) based on the
> > updated CPUID settings.
> >
> > Signed-off-by: Xiaoyao Li <xiaoyao.li@xxxxxxxxx>
>
> I would prefer to keep the kvm_update_cpuid name for what you called
> kvm_update_vcpu_model(), and rename the rest to kvm_update_cpuid_runtime().

But there is no CPUID being updated in kvm_update_cpuid(), after 
kvm_update_cpuid_runtime() is split out. This is confusing, IMO.

> Paolo
>
> > ---
> >   arch/x86/kvm/cpuid.c | 38 ++++++++++++++++++++++++--------------
> >   arch/x86/kvm/cpuid.h |  1 +
> >   arch/x86/kvm/x86.c   |  1 +
> >   3 files changed, 26 insertions(+), 14 deletions(-)
> >
> > diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
> > index a825878b7f84..001f5a94880e 100644
> > --- a/arch/x86/kvm/cpuid.c
> > +++ b/arch/x86/kvm/cpuid.c
> > @@ -76,7 +76,6 @@ static int kvm_check_cpuid(struct kvm_vcpu *vcpu)
> >   void kvm_update_cpuid(struct kvm_vcpu *vcpu)
> >   {
> >   	struct kvm_cpuid_entry2 *best;
> > -	struct kvm_lapic *apic = vcpu->arch.apic;
> >   
> >   	best = kvm_find_cpuid_entry(vcpu, 1, 0);
> >   	if (best) {
> > @@ -89,26 +88,14 @@ void kvm_update_cpuid(struct kvm_vcpu *vcpu)
> >   			   vcpu->arch.apic_base & MSR_IA32_APICBASE_ENABLE);
> >   	}
> >   
> > -	if (best && apic) {
> > -		if (cpuid_entry_has(best, X86_FEATURE_TSC_DEADLINE_TIMER))
> > -			apic->lapic_timer.timer_mode_mask = 3 << 17;
> > -		else
> > -			apic->lapic_timer.timer_mode_mask = 1 << 17;
> > -	}
> > -
> >   	best = kvm_find_cpuid_entry(vcpu, 7, 0);
> >   	if (best && boot_cpu_has(X86_FEATURE_PKU) && best->function == 0x7)
> >   		cpuid_entry_change(best, X86_FEATURE_OSPKE,
> >   				   kvm_read_cr4_bits(vcpu, X86_CR4_PKE));
> >   
> >   	best = kvm_find_cpuid_entry(vcpu, 0xD, 0);
> > -	if (!best) {
> > -		vcpu->arch.guest_supported_xcr0 = 0;
> > -	} else {
> > -		vcpu->arch.guest_supported_xcr0 =
> > -			(best->eax | ((u64)best->edx << 32)) & supported_xcr0;
> > +	if (best)
> >   		best->ebx = xstate_required_size(vcpu->arch.xcr0, false);
> > -	}
> >   
> >   	best = kvm_find_cpuid_entry(vcpu, 0xD, 1);
> >   	if (best && (cpuid_entry_has(best, X86_FEATURE_XSAVES) ||
> > @@ -127,6 +114,27 @@ void kvm_update_cpuid(struct kvm_vcpu *vcpu)
> >   					   vcpu->arch.ia32_misc_enable_msr &
> >   					   MSR_IA32_MISC_ENABLE_MWAIT);
> >   	}
> > +}
> > +
> > +void kvm_update_vcpu_model(struct kvm_vcpu *vcpu)
> > +{
> > +	struct kvm_lapic *apic = vcpu->arch.apic;
> > +	struct kvm_cpuid_entry2 *best;
> > +
> > +	best = kvm_find_cpuid_entry(vcpu, 1, 0);
> > +	if (best && apic) {
> > +		if (cpuid_entry_has(best, X86_FEATURE_TSC_DEADLINE_TIMER))
> > +			apic->lapic_timer.timer_mode_mask = 3 << 17;
> > +		else
> > +			apic->lapic_timer.timer_mode_mask = 1 << 17;
> > +	}
> > +
> > +	best = kvm_find_cpuid_entry(vcpu, 0xD, 0);
> > +	if (!best)
> > +		vcpu->arch.guest_supported_xcr0 = 0;
> > +	else
> > +		vcpu->arch.guest_supported_xcr0 =
> > +			(best->eax | ((u64)best->edx << 32)) & supported_xcr0;
> >   
> >   	/* Note, maxphyaddr must be updated before tdp_level. */
> >   	vcpu->arch.maxphyaddr = cpuid_query_maxphyaddr(vcpu);
> > @@ -218,6 +226,7 @@ int kvm_vcpu_ioctl_set_cpuid(struct kvm_vcpu *vcpu,
> >   	kvm_apic_set_version(vcpu);
> >   	kvm_x86_ops.cpuid_update(vcpu);
> >   	kvm_update_cpuid(vcpu);
> > +	kvm_update_vcpu_model(vcpu);
> >   
> >   	kvfree(cpuid_entries);
> >   out:
> > @@ -247,6 +256,7 @@ int kvm_vcpu_ioctl_set_cpuid2(struct kvm_vcpu *vcpu,
> >   	kvm_apic_set_version(vcpu);
> >   	kvm_x86_ops.cpuid_update(vcpu);
> >   	kvm_update_cpuid(vcpu);
> > +	kvm_update_vcpu_model(vcpu);
> >   out:
> >   	return r;
> >   }
> > diff --git a/arch/x86/kvm/cpuid.h b/arch/x86/kvm/cpuid.h
> > index f136de1debad..45e3643e2fba 100644
> > --- a/arch/x86/kvm/cpuid.h
> > +++ b/arch/x86/kvm/cpuid.h
> > @@ -10,6 +10,7 @@ extern u32 kvm_cpu_caps[NCAPINTS] __read_mostly;
> >   void kvm_set_cpu_caps(void);
> >   
> >   void kvm_update_cpuid(struct kvm_vcpu *vcpu);
> > +void kvm_update_vcpu_model(struct kvm_vcpu *vcpu);
> >   struct kvm_cpuid_entry2 *kvm_find_cpuid_entry(struct kvm_vcpu *vcpu,
> >   					      u32 function, u32 index);
> >   int kvm_dev_ioctl_get_cpuid(struct kvm_cpuid2 *cpuid,
> > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> > index 09ee54f5e385..6f376392e6e6 100644
> > --- a/arch/x86/kvm/x86.c
> > +++ b/arch/x86/kvm/x86.c
> > @@ -8184,6 +8184,7 @@ static void enter_smm(struct kvm_vcpu *vcpu)
> >   #endif
> >   
> >   	kvm_update_cpuid(vcpu);
> > +	kvm_update_vcpu_model(vcpu);
> >   	kvm_mmu_reset_context(vcpu);
> >   }
> >