Re: [PATCH v3 05/37] KVM: x86: Export kvm_propagate_fault() (as kvm_inject_emulated_page_fault)

From: Sean Christopherson <sean.j.christopherson@intel.com>
To: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
	Wanpeng Li <wanpengli@tencent.com>,
	Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
	kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
	Ben Gardon <bgardon@google.com>,
	Junaid Shahid <junaids@google.com>,
	Liran Alon <liran.alon@oracle.com>,
	Boris Ostrovsky <boris.ostrovsky@oracle.com>,
	John Haxby <john.haxby@oracle.com>,
	Miaohe Lin <linmiaohe@huawei.com>,
	Tom Lendacky <thomas.lendacky@amd.com>
Subject: Re: [PATCH v3 05/37] KVM: x86: Export kvm_propagate_fault() (as kvm_inject_emulated_page_fault)
Date: Mon, 23 Mar 2020 09:24:33 -0700	[thread overview]
Message-ID: <20200323162433.GM28711@linux.intel.com> (raw)
In-Reply-To: <87sghz844a.fsf@vitty.brq.redhat.com>

On Mon, Mar 23, 2020 at 04:47:49PM +0100, Vitaly Kuznetsov wrote:
> Sean Christopherson <sean.j.christopherson@intel.com> writes:
> 
> > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> > index e54c6ad628a8..64ed6e6e2b56 100644
> > --- a/arch/x86/kvm/x86.c
> > +++ b/arch/x86/kvm/x86.c
> > @@ -611,8 +611,11 @@ void kvm_inject_page_fault(struct kvm_vcpu *vcpu, struct x86_exception *fault)
> >  }
> >  EXPORT_SYMBOL_GPL(kvm_inject_page_fault);
> >  
> > -static bool kvm_propagate_fault(struct kvm_vcpu *vcpu, struct x86_exception *fault)
> > +bool kvm_inject_emulated_page_fault(struct kvm_vcpu *vcpu,
> > +				    struct x86_exception *fault)
> >  {
> > +	WARN_ON_ONCE(fault->vector != PF_VECTOR);
> > +
> >  	if (mmu_is_nested(vcpu) && !fault->nested_page_fault)
> >  		vcpu->arch.nested_mmu.inject_page_fault(vcpu, fault);
> >  	else
> > @@ -620,6 +623,7 @@ static bool kvm_propagate_fault(struct kvm_vcpu *vcpu, struct x86_exception *fau
> >  
> >  	return fault->nested_page_fault;
> >  }
> > +EXPORT_SYMBOL_GPL(kvm_inject_emulated_page_fault);
> 
> We don't seem to use the return value a lot, actually,
> inject_emulated_exception() seems to be the only one, the rest just call
> it without checking the return value. Judging by the new name, I'd guess
> that the function returns whether it was able to inject the exception or
> not but this doesn't seem to be the case. My suggestion would then be to
> make it return 'void' and return 'fault->nested_page_fault' separately
> in inject_emulated_exception().

Oooh, I like that idea.  The return from the common helper also confuses me
every time I look at it.

> >  void kvm_inject_nmi(struct kvm_vcpu *vcpu)
> >  {
> > @@ -6373,7 +6377,7 @@ static bool inject_emulated_exception(struct kvm_vcpu *vcpu)
> >  {
> >  	struct x86_emulate_ctxt *ctxt = vcpu->arch.emulate_ctxt;
> >  	if (ctxt->exception.vector == PF_VECTOR)
> > -		return kvm_propagate_fault(vcpu, &ctxt->exception);
> > +		return kvm_inject_emulated_page_fault(vcpu, &ctxt->exception);
> >  
> >  	if (ctxt->exception.error_code_valid)
> >  		kvm_queue_exception_e(vcpu, ctxt->exception.vector,
> 
> With or without the change suggested above,
> 
> Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
> 
> -- 
> Vitaly
> 