linux-kernel - Re: [PATCH v2 19/25] KVM: x86/mmu: simplify and/or inline computation of shadow MMU roles

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Date:   Tue, 8 Mar 2022 19:41:36 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        dmatlack@...gle.com
Subject: Re: [PATCH v2 19/25] KVM: x86/mmu: simplify and/or inline
 computation of shadow MMU roles

On Tue, Mar 08, 2022, Sean Christopherson wrote:
> On Mon, Feb 21, 2022, Paolo Bonzini wrote:
> > @@ -4822,18 +4798,23 @@ static void kvm_init_shadow_mmu(struct kvm_vcpu *vcpu,
> >  {
> >  	struct kvm_mmu *context = &vcpu->arch.root_mmu;
> >  	union kvm_mmu_paging_mode cpu_mode = kvm_calc_cpu_mode(vcpu, regs);
> > -	union kvm_mmu_page_role root_role =
> > -		kvm_calc_shadow_mmu_root_page_role(vcpu, cpu_mode);
> > +	union kvm_mmu_page_role root_role;
> >  
> > -	shadow_mmu_init_context(vcpu, context, cpu_mode, root_role);
> > -}
> > +	root_role = cpu_mode.base;
> > +	root_role.level = max_t(u32, root_role.level, PT32E_ROOT_LEVEL);
> 
> Heh, we have different definitions of "simpler".   Can we split the difference
> and do?
> 
> 	/* KVM uses PAE paging whenever the guest isn't using 64-bit paging. */
> 	if (!____is_efer_lma(regs))
> 		root_role.level = PT32E_ROOT_LEVEL;

Ha, and then the very next patch stomps all over this.  I think this just needs
to add

	BUILD_MMU_ROLE_ACCESSOR(ext, efer, lma);

and do

	if (!is_efer_lma(context))
		root_role.level = PT32E_ROOT_LEVEL;