linux-kernel - Re: [PATCH v9 5/6] KVM: x86: Migrate to __kvm_follow

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Date:   Tue, 3 Oct 2023 13:58:45 -0700
From:   Sean Christopherson <seanjc@...gle.com>
To:     Maxim Levitsky <mlevitsk@...hat.com>
Cc:     David Stevens <stevensd@...omium.org>,
        Yu Zhang <yu.c.zhang@...ux.intel.com>,
        Isaku Yamahata <isaku.yamahata@...il.com>,
        Zhi Wang <zhi.wang.linux@...il.com>, kvmarm@...ts.linux.dev,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: Re: [PATCH v9 5/6] KVM: x86: Migrate to __kvm_follow_pfn

On Tue, Oct 03, 2023, Maxim Levitsky wrote:
> У пн, 2023-09-11 у 11:16 +0900, David Stevens пише:
> > From: David Stevens <stevensd@...omium.org>
> > @@ -4283,12 +4290,20 @@ static int __kvm_faultin_pfn(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault
> >  			return RET_PF_EMULATE;
> >  	}
> >  
> > -	async = false;
> > -	fault->pfn = __gfn_to_pfn_memslot(slot, fault->gfn, false, false, &async,
> > -					  fault->write, &fault->map_writable,
> > -					  &fault->hva);
> > -	if (!async)
> > -		return RET_PF_CONTINUE; /* *pfn has correct page already */
> > +	foll.flags |= FOLL_NOWAIT;
> > +	fault->pfn = __kvm_follow_pfn(&foll);
> > +
> > +	if (!is_error_noslot_pfn(fault->pfn))
> > +		goto success;
> Unrelated but I can't say I like the 'is_error_noslot_pfn()' name, 
> I wish it was called something like is_valid_pfn().

I don't love the name either, but is_valid_pfn() would be extremely confusing
because the kernel already provides pfn_valid() to identify pfns/pages that are
managed by the kernel.  Trying to shove "guest" somewhere in the name also gets
confusing because it's a host pfn, not a guest pfn.