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Date:   Thu, 3 Mar 2022 08:14:42 +0100
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Subject: Re: [PATCH v2 4/7] KVM: x86/mmu: Zap only obsolete roots if a root
 shadow page is zapped
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To:     Sean Christopherson <seanjc@google.com>
Cc:     Christian Borntraeger <borntraeger@linux.ibm.com>,
        Janosch Frank <frankja@linux.ibm.com>,
        David Hildenbrand <david@redhat.com>,
        Claudio Imbrenda <imbrenda@linux.ibm.com>,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        Wanpeng Li <wanpengli@tencent.com>,
        Jim Mattson <jmattson@google.com>,
        Joerg Roedel <joro@8bytes.org>, kvm@vger.kernel.org,
        linux-kernel@vger.kernel.org, Ben Gardon <bgardon@google.com>,
        Lai Jiangshan <jiangshanlai@gmail.com>
References: <20220225182248.3812651-1-seanjc@google.com>
 <20220225182248.3812651-5-seanjc@google.com>
 <40a22c39-9da4-6c37-8ad0-b33970e35a2b@redhat.com>
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 <217cc048-8ca7-2b7b-141f-f44f0d95eec5@redhat.com>
 <Yh/1hPMhqeFKO0ih@google.com>
From:   Paolo Bonzini <pbonzini@redhat.com>
In-Reply-To: <Yh/1hPMhqeFKO0ih@google.com>
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On 3/2/22 23:53, Sean Christopherson wrote:
>>
>> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
>> index c5e3f219803e..7899ca4748c7 100644
>> --- a/arch/x86/kvm/svm/svm.c
>> +++ b/arch/x86/kvm/svm/svm.c
>> @@ -3857,6 +3857,9 @@ static void svm_load_mmu_pgd(struct kvm_vcpu *vcpu,
>> hpa_t root_hpa,
>>          unsigned long cr3;
>>
>>          if (npt_enabled) {
>> +               if (is_tdp_mmu_root(root_hpa))
>> +                       svm->current_vmcb->asid_generation = 0;
>> +
>>                  svm->vmcb->control.nested_cr3 = __sme_set(root_hpa);
>>                  vmcb_mark_dirty(svm->vmcb, VMCB_NPT);
>>
>> Why not just new_asid
> My mental coin flip came up tails?  new_asid() is definitely more intuitive.
> 

Can you submit a patch (seems like 5.17+stable material)?

Paolo