linux-kernel - [PATCH AUTOSEL 5.1 93/95] KVM: arm/arm64: Fix emulated ptimer irq injection

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Message-Id: <20190627003021.19867-93-sashal@kernel.org>
Date:   Wed, 26 Jun 2019 20:30:18 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Andrew Jones <drjones@...hat.com>,
        Marc Zyngier <marc.zyngier@....com>,
        Sasha Levin <sashal@...nel.org>, kvmarm@...ts.cs.columbia.edu
Subject: [PATCH AUTOSEL 5.1 93/95] KVM: arm/arm64: Fix emulated ptimer irq injection

From: Andrew Jones <drjones@...hat.com>

[ Upstream commit e4e5a865e9a9e8e47ac1959b629e9f3ae3b062f2 ]

The emulated ptimer needs to track the level changes, otherwise the
the interrupt will never get deasserted, resulting in the guest getting
stuck in an interrupt storm if it enables ptimer interrupts. This was
found with kvm-unit-tests; the ptimer tests hung as soon as interrupts
were enabled. Typical Linux guests don't have a problem as they prefer
using the virtual timer.

Fixes: bee038a674875 ("KVM: arm/arm64: Rework the timer code to use a timer_map")
Signed-off-by: Andrew Jones <drjones@...hat.com>
[Simplified the patch to res we only care about emulated timers here]
Signed-off-by: Marc Zyngier <marc.zyngier@....com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 virt/kvm/arm/arch_timer.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/virt/kvm/arm/arch_timer.c b/virt/kvm/arm/arch_timer.c
index 7fc272ecae16..1b1c449ceaf4 100644
--- a/virt/kvm/arm/arch_timer.c
+++ b/virt/kvm/arm/arch_timer.c
@@ -321,14 +321,15 @@ static void kvm_timer_update_irq(struct kvm_vcpu *vcpu, bool new_level,
 	}
 }
 
+/* Only called for a fully emulated timer */
 static void timer_emulate(struct arch_timer_context *ctx)
 {
 	bool should_fire = kvm_timer_should_fire(ctx);
 
 	trace_kvm_timer_emulate(ctx, should_fire);
 
-	if (should_fire) {
-		kvm_timer_update_irq(ctx->vcpu, true, ctx);
+	if (should_fire != ctx->irq.level) {
+		kvm_timer_update_irq(ctx->vcpu, should_fire, ctx);
 		return;
 	}
 
-- 
2.20.1