linux-kernel - Re: [PATCH v19 081/130] KVM: x86: Allow to update cached values in kvm_user_return

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Date: Fri, 12 Apr 2024 13:23:05 -0700
From: Isaku Yamahata <isaku.yamahata@...el.com>
To: Binbin Wu <binbin.wu@...ux.intel.com>
Cc: isaku.yamahata@...el.com, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org, isaku.yamahata@...il.com,
	Paolo Bonzini <pbonzini@...hat.com>, erdemaktas@...gle.com,
	Sean Christopherson <seanjc@...gle.com>,
	Sagi Shahar <sagis@...gle.com>, Kai Huang <kai.huang@...el.com>,
	chen.bo@...el.com, hang.yuan@...el.com, tina.zhang@...el.com,
	Chao Gao <chao.gao@...el.com>, isaku.yamahata@...ux.intel.com
Subject: Re: [PATCH v19 081/130] KVM: x86: Allow to update cached values in
 kvm_user_return_msrs w/o wrmsr

On Sun, Apr 07, 2024 at 01:36:46PM +0800,
Binbin Wu <binbin.wu@...ux.intel.com> wrote:

> > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> > index b361d948140f..1b189e86a1f1 100644
> > --- a/arch/x86/kvm/x86.c
> > +++ b/arch/x86/kvm/x86.c
> > @@ -440,6 +440,15 @@ static void kvm_user_return_msr_cpu_online(void)
> >   	}
> >   }
> > +static void kvm_user_return_register_notifier(struct kvm_user_return_msrs *msrs)
> > +{
> > +	if (!msrs->registered) {
> > +		msrs->urn.on_user_return = kvm_on_user_return;
> > +		user_return_notifier_register(&msrs->urn);
> > +		msrs->registered = true;
> > +	}
> > +}
> > +
> >   int kvm_set_user_return_msr(unsigned slot, u64 value, u64 mask)
> >   {
> >   	unsigned int cpu = smp_processor_id();
> > @@ -454,15 +463,21 @@ int kvm_set_user_return_msr(unsigned slot, u64 value, u64 mask)
> >   		return 1;
> >   	msrs->values[slot].curr = value;
> > -	if (!msrs->registered) {
> > -		msrs->urn.on_user_return = kvm_on_user_return;
> > -		user_return_notifier_register(&msrs->urn);
> > -		msrs->registered = true;
> > -	}
> > +	kvm_user_return_register_notifier(msrs);
> >   	return 0;
> >   }
> >   EXPORT_SYMBOL_GPL(kvm_set_user_return_msr);
> > +/* Update the cache, "curr", and register the notifier */
> Not sure this comment is necessary, since the code is simple.

Ok, let's remove it.


> > +void kvm_user_return_update_cache(unsigned int slot, u64 value)
> 
> As a public API, is it better to use "kvm_user_return_msr_update_cache"
> instead of "kvm_user_return_update_cache"?
> Although it makes the API name longer...

Yes, other functions consistently user user_return_msr. We should do so.
-- 
Isaku Yamahata <isaku.yamahata@...el.com>