linux-kernel - [PATCH 4.9 28/32] KVM: nSVM: clear events pending from svm_complete

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Message-Id: <20190304081604.373320084@linuxfoundation.org>
Date:   Mon,  4 Mar 2019 09:22:16 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Vitaly Kuznetsov <vkuznets@...hat.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.9 28/32] KVM: nSVM: clear events pending from svm_complete_interrupts() when exiting to L1

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

[ Upstream commit 619ad846fc3452adaf71ca246c5aa711e2055398 ]

kvm-unit-tests' eventinj "NMI failing on IDT" test results in NMI being
delivered to the host (L1) when it's running nested. The problem seems to
be: svm_complete_interrupts() raises 'nmi_injected' flag but later we
decide to reflect EXIT_NPF to L1. The flag remains pending and we do NMI
injection upon entry so it got delivered to L1 instead of L2.

It seems that VMX code solves the same issue in prepare_vmcs12(), this was
introduced with code refactoring in commit 5f3d5799974b ("KVM: nVMX: Rework
event injection and recovery").

Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 arch/x86/kvm/svm.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index afc2bd03b4d9e..01eb0451b96d3 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -2862,6 +2862,14 @@ static int nested_svm_vmexit(struct vcpu_svm *svm)
 	kvm_mmu_reset_context(&svm->vcpu);
 	kvm_mmu_load(&svm->vcpu);

+	/*
+	 * Drop what we picked up for L2 via svm_complete_interrupts() so it
+	 * doesn't end up in L1.
+	 */
+	svm->vcpu.arch.nmi_injected = false;
+	kvm_clear_exception_queue(&svm->vcpu);
+	kvm_clear_interrupt_queue(&svm->vcpu);
+
 	return 0;
 }

-- 
2.19.1