linux-kernel - [PATCH] Revert "KVM: x86: Unconditionally enable irqs in guest context"

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Message-Id: <20210105192844.296277-1-nitesh@redhat.com>
Date:   Tue,  5 Jan 2021 14:28:44 -0500
From:   Nitesh Narayan Lal <nitesh@...hat.com>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        seanjc@...gle.com, w90p710@...il.com, pbonzini@...hat.com,
        vkuznets@...hat.com, nitesh@...hat.com
Subject: [PATCH] Revert "KVM: x86: Unconditionally enable irqs in guest context"

This reverts commit d7a08882a0a4b4e176691331ee3f492996579534.

After the introduction of the patch:

	87fa7f3e9: x86/kvm: Move context tracking where it belongs

since we have moved guest_exit_irqoff closer to the VM-Exit, explicit
enabling of irqs to process pending interrupts should not be required
within vcpu_enter_guest anymore.

Conflicts:
	arch/x86/kvm/svm.c

Signed-off-by: Nitesh Narayan Lal <nitesh@...hat.com>
---
 arch/x86/kvm/svm/svm.c |  9 +++++++++
 arch/x86/kvm/x86.c     | 11 -----------
 2 files changed, 9 insertions(+), 11 deletions(-)

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index cce0143a6f80..c9b2fbb32484 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -4187,6 +4187,15 @@ static int svm_check_intercept(struct kvm_vcpu *vcpu,
 
 static void svm_handle_exit_irqoff(struct kvm_vcpu *vcpu)
 {
+	kvm_before_interrupt(vcpu);
+	local_irq_enable();
+	/*
+	 * We must have an instruction with interrupts enabled, so
+	 * the timer interrupt isn't delayed by the interrupt shadow.
+	 */
+	asm("nop");
+	local_irq_disable();
+	kvm_after_interrupt(vcpu);
 }
 
 static void svm_sched_in(struct kvm_vcpu *vcpu, int cpu)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 3f7c1fc7a3ce..3e17c9ffcad8 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -9023,18 +9023,7 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
 
 	kvm_x86_ops.handle_exit_irqoff(vcpu);
 
-	/*
-	 * Consume any pending interrupts, including the possible source of
-	 * VM-Exit on SVM and any ticks that occur between VM-Exit and now.
-	 * An instruction is required after local_irq_enable() to fully unblock
-	 * interrupts on processors that implement an interrupt shadow, the
-	 * stat.exits increment will do nicely.
-	 */
-	kvm_before_interrupt(vcpu);
-	local_irq_enable();
 	++vcpu->stat.exits;
-	local_irq_disable();
-	kvm_after_interrupt(vcpu);
 
 	if (lapic_in_kernel(vcpu)) {
 		s64 delta = vcpu->arch.apic->lapic_timer.advance_expire_delta;
-- 
2.27.0