linux-kernel - Re: [PATCH v3 4/8] KVM: X86: Split kvm_update

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Message-ID: <92184f05-ca27-268c-ea72-f939fb1a0ab2@intel.com>
Date:   Wed, 8 Jul 2020 20:33:02 +0800
From:   Xiaoyao Li <xiaoyao.li@...el.com>
To:     Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Jim Mattson <jmattson@...gle.com>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org, Jonathan Corbet <corbet@....net>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Joerg Roedel <joro@...tes.org>
Subject: Re: [PATCH v3 4/8] KVM: X86: Split kvm_update_cpuid()

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@...el.com>
> 
> 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);
>>   }
>>   
>>
>