linux-kernel - Re: [RFC PATCH V3 3/4] KVM: X86: Alloc role.pae

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Message-ID: <658729a1-a4a1-a353-50d6-ef71e83a4375@redhat.com>
Date:   Thu, 14 Apr 2022 12:04:20 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Lai Jiangshan <jiangshanlai@...il.com>
Cc:     Sean Christopherson <seanjc@...gle.com>,
        LKML <linux-kernel@...r.kernel.org>, kvm@...r.kernel.org,
        Lai Jiangshan <jiangshan.ljs@...group.com>,
        Jonathan Corbet <corbet@....net>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        X86 ML <x86@...nel.org>, "H. Peter Anvin" <hpa@...or.com>,
        linux-doc@...r.kernel.org
Subject: Re: [RFC PATCH V3 3/4] KVM: X86: Alloc role.pae_root shadow page

On 4/14/22 11:32, Lai Jiangshan wrote:
> kvm_mmu_free_roots() can not free those new types of sp if they are still
> valid.  And different vcpu can use the same pae root sp if the guest cr3
> of the vcpus are the same.

Right, but then load_pdptrs only needs to zap the page before (or 
instead of) calling kvm_mmu_free_roots().

Paolo

> And new pae root can be put in prev_root too (not implemented yet)
> because they are not too special anymore.  As long as sp->gfn, sp->pae_off,
> sp->role are matched, they can be reused.