linux-kernel - [PATCH AUTOSEL for 4.14 015/100] KVM: nVMX: Fix vmx_check_nested_events() return value in case an event was reinjected to L2

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Message-ID: <20180124041414.32065-15-alexander.levin@microsoft.com>
Date:   Wed, 24 Jan 2018 04:14:29 +0000
From:   Sasha Levin <Alexander.Levin@...rosoft.com>
To:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
CC:     Liran Alon <liran.alon@...cle.com>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Sasha Levin <Alexander.Levin@...rosoft.com>
Subject: [PATCH AUTOSEL for 4.14 015/100] KVM: nVMX: Fix
 vmx_check_nested_events() return value in case an event was reinjected to L2

From: Liran Alon <liran.alon@...cle.com>

[ Upstream commit 917dc6068bc12a2dafffcf0e9d405ddb1b8780cb ]

vmx_check_nested_events() should return -EBUSY only in case there is a
pending L1 event which requires a VMExit from L2 to L1 but such a
VMExit is currently blocked. Such VMExits are blocked either
because nested_run_pending=1 or an event was reinjected to L2.
vmx_check_nested_events() should return 0 in case there are no
pending L1 events which requires a VMExit from L2 to L1 or if
a VMExit from L2 to L1 was done internally.

However, upstream commit which introduced blocking in case an event was
reinjected to L2 (commit acc9ab601327 ("KVM: nVMX: Fix pending events
injection")) contains a bug: It returns -EBUSY even if there are no
pending L1 events which requires VMExit from L2 to L1.

This commit fix this issue.

Fixes: acc9ab601327 ("KVM: nVMX: Fix pending events injection")

Signed-off-by: Liran Alon <liran.alon@...cle.com>
Reviewed-by: Nikita Leshenko <nikita.leshchenko@...cle.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Signed-off-by: Radim Krčmář <rkrcmar@...hat.com>
Signed-off-by: Sasha Levin <alexander.levin@...rosoft.com>
---
 arch/x86/kvm/vmx.c | 13 ++++++-------
 1 file changed, 6 insertions(+), 7 deletions(-)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 3a16e45f0c2e..d073f91bc089 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -11114,13 +11114,12 @@ static int vmx_check_nested_events(struct kvm_vcpu *vcpu, bool external_intr)
 {
 	struct vcpu_vmx *vmx = to_vmx(vcpu);
 	unsigned long exit_qual;
-
-	if (kvm_event_needs_reinjection(vcpu))
-		return -EBUSY;
+	bool block_nested_events =
+	    vmx->nested.nested_run_pending || kvm_event_needs_reinjection(vcpu);
 
 	if (vcpu->arch.exception.pending &&
 		nested_vmx_check_exception(vcpu, &exit_qual)) {
-		if (vmx->nested.nested_run_pending)
+		if (block_nested_events)
 			return -EBUSY;
 		nested_vmx_inject_exception_vmexit(vcpu, exit_qual);
 		vcpu->arch.exception.pending = false;
@@ -11129,14 +11128,14 @@ static int vmx_check_nested_events(struct kvm_vcpu *vcpu, bool external_intr)
 
 	if (nested_cpu_has_preemption_timer(get_vmcs12(vcpu)) &&
 	    vmx->nested.preemption_timer_expired) {
-		if (vmx->nested.nested_run_pending)
+		if (block_nested_events)
 			return -EBUSY;
 		nested_vmx_vmexit(vcpu, EXIT_REASON_PREEMPTION_TIMER, 0, 0);
 		return 0;
 	}
 
 	if (vcpu->arch.nmi_pending && nested_exit_on_nmi(vcpu)) {
-		if (vmx->nested.nested_run_pending)
+		if (block_nested_events)
 			return -EBUSY;
 		nested_vmx_vmexit(vcpu, EXIT_REASON_EXCEPTION_NMI,
 				  NMI_VECTOR | INTR_TYPE_NMI_INTR |
@@ -11152,7 +11151,7 @@ static int vmx_check_nested_events(struct kvm_vcpu *vcpu, bool external_intr)
 
 	if ((kvm_cpu_has_interrupt(vcpu) || external_intr) &&
 	    nested_exit_on_intr(vcpu)) {
-		if (vmx->nested.nested_run_pending)
+		if (block_nested_events)
 			return -EBUSY;
 		nested_vmx_vmexit(vcpu, EXIT_REASON_EXTERNAL_INTERRUPT, 0, 0);
 		return 0;
-- 
2.11.0