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

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Date:   Wed, 9 Mar 2022 11:33:21 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Sean Christopherson <seanjc@...gle.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 3/8/22 20:35, Sean Christopherson wrote:
>> +	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;
> 

It's not that easy until the very end (when cpu_mode is set in 
kvm_mmu_init_walker), but I'll make sure to switch to is_efer_lma once 
it is possible.

Paolo