linux-kernel - Re: [PATCH v2 4/7] KVM: x86/mmu: Zap only obsolete roots if a root shadow page is zapped

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Date:   Thu, 3 Mar 2022 08:14:42 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Sean Christopherson <seanjc@...gle.com>
Cc:     Christian Borntraeger <borntraeger@...ux.ibm.com>,
        Janosch Frank <frankja@...ux.ibm.com>,
        David Hildenbrand <david@...hat.com>,
        Claudio Imbrenda <imbrenda@...ux.ibm.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, Ben Gardon <bgardon@...gle.com>,
        Lai Jiangshan <jiangshanlai@...il.com>
Subject: Re: [PATCH v2 4/7] KVM: x86/mmu: Zap only obsolete roots if a root
 shadow page is zapped

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