Re: [PATCH] KVM: Optimize kvm_arch_vcpu_ioctl_run function

[Tianjia Zhang]

On 2020/4/14 22:26, Vitaly Kuznetsov wrote:
> Tianjia Zhang <tianjia.zhang@xxxxxxxxxxxxxxxxx> 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@xxxxxxxxxxxxxxxxx>
> > ---
> >   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;
> >   	}