linux-kernel - Re: [PATCH V3 11/12] KVM: X86/MMU: Don't use mmu->pae_root when shadowing PAE NPT in 64-bit host

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Message-ID: <Ytc948/8kK18/d0d@google.com>
Date:   Tue, 19 Jul 2022 23:27:31 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Lai Jiangshan <jiangshanlai@...il.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        Paolo Bonzini <pbonzini@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Maxim Levitsky <mlevitsk@...hat.com>,
        David Matlack <dmatlack@...gle.com>,
        Lai Jiangshan <jiangshan.ljs@...group.com>
Subject: Re: [PATCH V3 11/12] KVM: X86/MMU: Don't use mmu->pae_root when
 shadowing PAE NPT in 64-bit host

On Tue, Jul 19, 2022, Sean Christopherson wrote:
> On Sat, May 21, 2022, Lai Jiangshan wrote:
> Actually, I think the series is buggy.  That patch, which precedes this one, does
> 
> 	if (vcpu->arch.mmu->root_role.level != PT32E_ROOT_LEVEL)
> 		return 0;
> 
> i.e. does NOT allocate pae_root for a 64-bit host, which means that running KVM
> against the on-demand patch would result in the WARN firing and bad things happening.

Gah, I take that back, pae_root is allocated by mmu_alloc_special_roots().