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From: Vitaly Kuznetsov <vkuznets@redhat.com>
To: kvm@vger.kernel.org, Paolo Bonzini <pbonzini@redhat.com>
Cc: linux-kernel@vger.kernel.org,
	Sean Christopherson <seanjc@google.com>,
	Wanpeng Li <wanpengli@tencent.com>,
	Jim Mattson <jmattson@google.com>,
	Maxim Levitsky <mlevitsk@redhat.com>
Subject: [PATCH 6/7] KVM: nVMX: Request to sync eVMCS from VMCS12 after migration
Date: Tue, 11 May 2021 13:19:55 +0200	[thread overview]
Message-ID: <20210511111956.1555830-7-vkuznets@redhat.com> (raw)
In-Reply-To: <20210511111956.1555830-1-vkuznets@redhat.com>

VMCS12 is used to keep the authoritative state during nested state
migration. In case 'need_vmcs12_to_shadow_sync' flag is set, we're
in between L2->L1 vmexit and L1 guest run when actual sync to
enlightened (or shadow) VMCS happens. Nested state, however, has
no flag for 'need_vmcs12_to_shadow_sync' so vmx_set_nested_state()->
set_current_vmptr() always sets it. Enlightened vmptrld path, however,
doesn't have the quirk so some VMCS12 changes may not get properly
reflected to eVMCS and L1 will see an incorrect state.

Note, during L2 execution or when need_vmcs12_to_shadow_sync is not
set the change is effectively a nop: in the former case all changes
will get reflected during the first L2->L1 vmexit and in the later
case VMCS12 and eVMCS are already in sync (thanks to
copy_enlightened_to_vmcs12() in vmx_get_nested_state()).

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
 arch/x86/kvm/vmx/nested.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 1661e2e19560..0a422c6091dc 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -3135,6 +3135,12 @@ static bool nested_get_evmcs_page(struct kvm_vcpu *vcpu)
 		if (evmptrld_status == EVMPTRLD_VMFAIL ||
 		    evmptrld_status == EVMPTRLD_ERROR)
 			return false;
+		/*
+		 * Post migration VMCS12 always provides the most actual
+		 * information, copy it to eVMCS upon entry.
+		 */
+		vmx->nested.need_vmcs12_to_shadow_sync = true;
 	return true;

  parent reply	other threads:[~2021-05-11 11:20 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-11 11:19 [PATCH 0/7] KVM: nVMX: Fixes for nested state migration when eVMCS is in use Vitaly Kuznetsov
2021-05-11 11:19 ` [PATCH 1/7] KVM: nVMX: Introduce nested_evmcs_is_used() Vitaly Kuznetsov
2021-05-11 11:19 ` [PATCH 2/7] KVM: nVMX: Release enlightened VMCS on VMCLEAR Vitaly Kuznetsov
2021-05-11 11:19 ` [PATCH 3/7] KVM: nVMX: Ignore 'hv_clean_fields' data when eVMCS data is copied in vmx_get_nested_state() Vitaly Kuznetsov
2021-05-11 16:37   ` Sean Christopherson
2021-05-12  7:14     ` Vitaly Kuznetsov
2021-05-11 11:19 ` [PATCH 4/7] KVM: nVMX: Force enlightened VMCS sync from nested_vmx_failValid() Vitaly Kuznetsov
2021-05-11 11:19 ` [PATCH 5/7] KVM: nVMX: Reset eVMCS clean fields data from prepare_vmcs02() Vitaly Kuznetsov
2021-05-11 16:32   ` Sean Christopherson
2021-05-12  7:19     ` Vitaly Kuznetsov
2021-05-11 11:19 ` Vitaly Kuznetsov [this message]
2021-05-11 11:19 ` [PATCH 7/7] KVM: selftests: evmcs_test: Test that KVM_STATE_NESTED_EVMCS is never lost Vitaly Kuznetsov

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