After applying preempt disable patch, i.e PATCH 1/2, Christian reported
a subsequent warning stopping his board to boot properly.
WARNING: at .kvmppc_fix_ee_before_entry+0x10/0x28, CPU#0: qemu-system-ppc/4667
CPU: 0 UID: 1000 PID: 4667 Comm: qemu-system-ppc Tainted: G W
7.3.0-rc4-2-powerpc64-smp #1 PREEMPT
Tainted: [W]=WARN
Hardware name: varisys,CYRUS5040 e5500 0x80240012 CoreNet Generic
NIP [c00000000005dc3c] .kvmppc_fix_ee_before_entry+0x10/0x28
LR [c00000000005f298] .kvmppc_handle_exit+0x5b4/0x5e8
Call Trace:
[c000000086587780] [c00000000005ee10] .kvmppc_handle_exit+0x12c/0x5e8
(unreliable)
[c000000086587830] [c000000000062068] .kvmppc_resume_host+0xb8/0x10c
It triggers below warning...
static inline void kvmppc_fix_ee_before_entry(void)
{
trace_hardirqs_on();
/*
* To avoid races, the caller must have gone directly from having
* interrupts fully-enabled to hard-disabled.
*/
WARN_ON(local_paca->irq_happened != PACA_IRQ_HARD_DIS);
This happens since kvmppc_prepare_to_enter does first local_irq_disable
followed by hard_irq_disable. This leaves a small window where interrupt
may occur and it could set the irq pending bit in PACA. When that
happens replay that interrupt before entering the guest.
Fixes: 12013e3d4695 ("KVM: powerpc: Use generic xfer to guest work function")
Reported-by: Christian Zigotzky <[email protected]>
Closes:
https://lore.kernel.org/all/[email protected]/
Signed-off-by: Shrikanth Hegde <[email protected]>
---
arch/powerpc/kvm/powerpc.c | 13 +++++++++++++
1 file changed, 13 insertions(+)
diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
index 9194cf492d1c..847ff07c364b 100644
--- a/arch/powerpc/kvm/powerpc.c
+++ b/arch/powerpc/kvm/powerpc.c
@@ -147,6 +147,19 @@ int kvmppc_prepare_to_enter(struct kvm_vcpu *vcpu)
continue;
}
+#ifdef CONFIG_PPC64
+ /*
+ * Interrupt arrived between the soft and hard
+ * disable. Replay it and retry guest entry.
+ */
+ if (unlikely(local_paca->irq_happened != PACA_IRQ_HARD_DIS)) {
+ local_irq_enable();
+ local_irq_disable();
+ hard_irq_disable();
+ continue;
+ }
+#endif
+
guest_enter_irqoff();
return 1;
}
--
2.52.0
