linux-kernel - Re: [PATCH v2 31/32] KVM: nVMX: Don't flush TLB on nested VM transition with EPT enabled

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Message-ID: <3c3a4d9b-b213-dfc0-2857-a975e9c20770@redhat.com>
Date:   Wed, 18 Mar 2020 18:11:28 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Sean Christopherson <sean.j.christopherson@...el.com>
Cc:     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>,
        Junaid Shahid <junaids@...gle.com>,
        Liran Alon <liran.alon@...cle.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        John Haxby <john.haxby@...cle.com>,
        Miaohe Lin <linmiaohe@...wei.com>,
        Tom Lendacky <thomas.lendacky@....com>
Subject: Re: [PATCH v2 31/32] KVM: nVMX: Don't flush TLB on nested VM
 transition with EPT enabled

On 18/03/20 18:02, Sean Christopherson wrote:
> So something like this?
> 
> 	if (!nested_ept)
> 		kvm_mmu_new_cr3(vcpu, cr3, enable_ept ||
> 					   nested_cpu_has_vpid(vmcs12));

... which is exactly nested_has_guest_tlb_tag(vcpu).  Well, not exactly
but it's a bug in your code above. :)

It completely makes sense to use that as the third argument, and while a
comment is still needed it will be much smaller.

Paolo