powerpc/xive: Discard disabled interrupts in get_irqchip_state()

When an interrupt is passed through, the KVM XIVE device calls the
set_vcpu_affinity() handler which raises the P bit to mask the
interrupt and to catch any in-flight interrupts while routing the
interrupt to the guest.

On the guest side, drivers (like some Intels) can request at probe
time some MSIs and call synchronize_irq() to check that there are no
in flight interrupts. This will call the XIVE get_irqchip_state()
handler which will always return true as the interrupt P bit has been
set on the host side and lock the CPU in an infinite loop.

Fix that by discarding disabled interrupts in get_irqchip_state().

Fixes: da15c03 ("powerpc/xive: Implement get_irqchip_state method for XIVE to fix shutdown race")
Cc: [email protected] #v5.4+
Signed-off-by: Cédric Le Goater <[email protected]>
Tested-by: seeteena <[email protected]>
Signed-off-by: Michael Ellerman <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

arch/powerpc/sysdev/xive/common.c

@@ -945,7 +945,8 @@ static int xive_get_irqchip_state(struct irq_data *data,
 		 * interrupt to be inactive in that case.
 		 */
 		*state = (pq != XIVE_ESB_INVALID) && !xd->stale_p &&
-			(xd->saved_p || !!(pq & XIVE_ESB_VAL_P));
+			(xd->saved_p || (!!(pq & XIVE_ESB_VAL_P) &&
+			 !irqd_irq_disabled(data)));
 		return 0;
 	default:
 		return -EINVAL;