linux-kernel - [PATCH] KVM: arm64: Fix CPUHP logic for protected KVM

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Message-ID: <20230719175400.647154-1-rananta@google.com>
Date:   Wed, 19 Jul 2023 17:54:00 +0000
From:   Raghavendra Rao Ananta <rananta@...gle.com>
To:     Oliver Upton <oliver.upton@...ux.dev>,
        Marc Zyngier <maz@...nel.org>
Cc:     James Morse <james.morse@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Will Deacon <will@...nel.org>, Fuad Tabba <tabba@...gle.com>,
        Jing Zhang <jingzhangos@...gle.com>,
        Colton Lewis <coltonlewis@...gle.com>,
        Reiji Watanabe <reijiw@...gle.com>,
        Raghavendra Rao Anata <rananta@...gle.com>,
        kvmarm@...ts.linux.dev, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org
Subject: [PATCH] KVM: arm64: Fix CPUHP logic for protected KVM

For protected kvm, the CPU hotplug 'down' logic currently brings
down the timer and vGIC, essentially disabling interrupts. However,
because of how the 'kvm_arm_hardware_enabled' flag is designed, it
never re-enables them back on the CPU hotplug 'up' path. Hence,
clean up the logic to maintain the CPU hotplug up/down symmetry.

Fixes: 466d27e48d7c ("KVM: arm64: Simplify the CPUHP logic")
Reported-by: Oliver Upton <oliver.upton@...ux.dev>
Suggested-by: Oliver Upton <oliver.upton@...ux.dev>
Signed-off-by: Raghavendra Rao Ananta <rananta@...gle.com>
---
 arch/arm64/kvm/arm.c | 14 ++++----------
 1 file changed, 4 insertions(+), 10 deletions(-)

diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index c2c14059f6a8..010ebfa69650 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -1867,14 +1867,10 @@ static void _kvm_arch_hardware_enable(void *discard)
 
 int kvm_arch_hardware_enable(void)
 {
-	int was_enabled = __this_cpu_read(kvm_arm_hardware_enabled);
-
 	_kvm_arch_hardware_enable(NULL);
 
-	if (!was_enabled) {
-		kvm_vgic_cpu_up();
-		kvm_timer_cpu_up();
-	}
+	kvm_vgic_cpu_up();
+	kvm_timer_cpu_up();
 
 	return 0;
 }
@@ -1889,10 +1885,8 @@ static void _kvm_arch_hardware_disable(void *discard)
 
 void kvm_arch_hardware_disable(void)
 {
-	if (__this_cpu_read(kvm_arm_hardware_enabled)) {
-		kvm_timer_cpu_down();
-		kvm_vgic_cpu_down();
-	}
+	kvm_timer_cpu_down();
+	kvm_vgic_cpu_down();
 
 	if (!is_protected_kvm_enabled())
 		_kvm_arch_hardware_disable(NULL);
-- 
2.41.0.487.g6d72f3e995-goog