linux-kernel - Re: [PATCH 0/4] KVM: nVMX: Fix migration of nested guests when eVMCS is in use

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Message-ID: <f2f7020d-9293-d9bb-093f-b9c857a962d8@redhat.com>
Date:   Mon, 3 May 2021 17:43:30 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Vitaly Kuznetsov <vkuznets@...hat.com>, kvm@...r.kernel.org
Cc:     Sean Christopherson <seanjc@...gle.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Maxim Levitsky <mlevitsk@...hat.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/4] KVM: nVMX: Fix migration of nested guests when eVMCS
 is in use

On 03/05/21 17:08, Vitaly Kuznetsov wrote:
> Win10 guests with WSL2 enabled sometimes crash on migration when
> enlightened VMCS was used. The condition seems to be induced by the
> situation when L2->L1 exit is caused immediately after migration and
> before L2 gets a chance to run (e.g. when there's an interrupt pending).

Interesting, I think it gets to nested_vmx_vmexit before

                 if (kvm_check_request(KVM_REQ_GET_NESTED_STATE_PAGES, vcpu)) {
                         if (unlikely(!kvm_x86_ops.nested_ops->get_nested_state_pages(vcpu))) {
                                 r = 0;
                                 goto out;
                         }
                 }

due to the infamous calls to check_nested_events that are scattered
through KVM?

Paolo