linux-kernel - Re: [PATCH] KVM: Optimize kvm_arch_vcpu_ioctl

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Date:   Wed, 15 Apr 2020 10:19:04 +0800
From:   Tianjia Zhang <tianjia.zhang@...ux.alibaba.com>
To:     Vitaly Kuznetsov <vkuznets@...hat.com>
Cc:     kvm@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        kvmarm@...ts.cs.columbia.edu, linux-kernel@...r.kernel.org,
        pbonzini@...hat.com, sean.j.christopherson@...el.com,
        wanpengli@...cent.com, jmattson@...gle.com, joro@...tes.org,
        tglx@...utronix.de, mingo@...hat.com, bp@...en8.de, x86@...nel.org,
        hpa@...or.com, maz@...nel.org, james.morse@....com,
        julien.thierry.kdev@...il.com, suzuki.poulose@....com
Subject: Re: [PATCH] KVM: Optimize kvm_arch_vcpu_ioctl_run function



On 2020/4/14 22:26, Vitaly Kuznetsov wrote:
> Tianjia Zhang <tianjia.zhang@...ux.alibaba.com> writes:
> 
>> kvm_arch_vcpu_ioctl_run() is only called in the file kvm_main.c,
>> where vcpu->run is the kvm_run parameter, so it has been replaced.
>>
>> Signed-off-by: Tianjia Zhang <tianjia.zhang@...ux.alibaba.com>
>> ---
>>   arch/x86/kvm/x86.c | 8 ++++----
>>   virt/kvm/arm/arm.c | 2 +-
>>   2 files changed, 5 insertions(+), 5 deletions(-)
>>
>> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
>> index 3bf2ecafd027..70e3f4abbd4d 100644
>> --- a/arch/x86/kvm/x86.c
>> +++ b/arch/x86/kvm/x86.c
>> @@ -8726,18 +8726,18 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
>>   		r = -EAGAIN;
>>   		if (signal_pending(current)) {
>>   			r = -EINTR;
>> -			vcpu->run->exit_reason = KVM_EXIT_INTR;
>> +			kvm_run->exit_reason = KVM_EXIT_INTR;
> 
> I have a more generic question: why do we need to pass 'kvm_run' to
> kvm_arch_vcpu_ioctl_run() if it can be extracted from 'struct kvm_vcpu'?
> The only call site looks like
> 
> virt/kvm/kvm_main.c:            r = kvm_arch_vcpu_ioctl_run(vcpu, vcpu->run);
> 

In the earlier version, kvm_run is used to pass parameters with user 
mode and is not included in the vcpu structure, so it has been retained 
until now.

Thanks,
Tianjia

>>   			++vcpu->stat.signal_exits;
>>   		}
>>   		goto out;
>>   	}
>>   
>> -	if (vcpu->run->kvm_valid_regs & ~KVM_SYNC_X86_VALID_FIELDS) {
>> +	if (kvm_run->kvm_valid_regs & ~KVM_SYNC_X86_VALID_FIELDS) {
>>   		r = -EINVAL;
>>   		goto out;
>>   	}
>>   
>> -	if (vcpu->run->kvm_dirty_regs) {
>> +	if (kvm_run->kvm_dirty_regs) {
>>   		r = sync_regs(vcpu);
>>   		if (r != 0)
>>   			goto out;
>> @@ -8767,7 +8767,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *kvm_run)
>>   
>>   out:
>>   	kvm_put_guest_fpu(vcpu);
>> -	if (vcpu->run->kvm_valid_regs)
>> +	if (kvm_run->kvm_valid_regs)
>>   		store_regs(vcpu);
>>   	post_kvm_run_save(vcpu);
>>   	kvm_sigset_deactivate(vcpu);
>> diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c
>> index 48d0ec44ad77..ab9d7966a4c8 100644
>> --- a/virt/kvm/arm/arm.c
>> +++ b/virt/kvm/arm/arm.c
>> @@ -659,7 +659,7 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run)
>>   		return ret;
>>   
>>   	if (run->exit_reason == KVM_EXIT_MMIO) {
>> -		ret = kvm_handle_mmio_return(vcpu, vcpu->run);
>> +		ret = kvm_handle_mmio_return(vcpu, run);
>>   		if (ret)
>>   			return ret;
>>   	}
>