linux-kernel - Re: [PATCH] x86/kvm/mmu: make mmu->prev

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Date:   Fri, 22 Feb 2019 21:29:28 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Vitaly Kuznetsov <vkuznets@...hat.com>, kvm@...r.kernel.org
Cc:     Radim Krčmář <rkrcmar@...hat.com>,
        Junaid Shahid <junaids@...gle.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86/kvm/mmu: make mmu->prev_roots cache work for NPT case

On 22/02/19 19:49, Vitaly Kuznetsov wrote:
>> Really cr4_pae means "are the PTEs 8 bytes".  So I think your patch is
>> correct but on top we should set it to 1 (not zero!!) for
>> kvm_calc_shadow_ept_root_page_role, init_kvm_nested_mmu and
>> kvm_calc_tdp_mmu_root_page_role.  Or maybe everything breaks with that
>> change.
>>
> Yes, exactly. If we put '1' there kvm_mmu_get_page() will again filter
> it out and we won't be able to find the root in prev_roots cache :-(
> 

Well, of course then kvm_mmu_get_page() would have to remove the filtering.

Paolo