Marc Zyngier [off-list ref] writes:

quoted

On Wed, 28 Apr 2021 15:00:15 +0100,
Alexandru Elisei [off-list ref] wrote:

quoted

I interpret that as that an INVALL guarantees that a change is
visible, but it the change can become visible even without the
INVALL.

Yes. Expecting the LPI to be delivered or not in the absence of an
invalidate when its configuration has been altered is wrong. The
architecture doesn't guarantee anything of the sort.

Is the underlying hypervisor allowed to invalidate and reload the
configuration whenever it wants or should it only be driven by the
guests requests?

I did consider a more nuanced variant of the test that allowed for a
delivery pre-inval and a pass for post-inval as long as it had been
delivered one way or another:

--8<---------------cut here---------------start------------->8---
modified   arm/gic.c

@@ -36,6 +36,7 @@ static struct gic *gic;
 static int acked[NR_CPUS], spurious[NR_CPUS];
 static int irq_sender[NR_CPUS], irq_number[NR_CPUS];
 static cpumask_t ready;
+static bool under_tcg;
 
 static void nr_cpu_check(int nr)
 {

@@ -687,6 +688,7 @@ static void test_its_trigger(void)
 	struct its_collection *col3;
 	struct its_device *dev2, *dev7;
 	cpumask_t mask;
+	bool before, after;
 
 	if (its_setup1())
 		return;

@@ -734,15 +736,17 @@ static void test_its_trigger(void)
 	/*
 	 * re-enable the LPI but willingly do not call invall
 	 * so the change in config is not taken into account.
-	 * The LPI should not hit
+	 * The LPI should not hit. This does however depend on
+	 * implementation defined behaviour - under QEMU TCG emulation
+	 * it can quite correctly process the event directly.
 	 */
 	gicv3_lpi_set_config(8195, LPI_PROP_DEFAULT);
 	stats_reset();
 	cpumask_clear(&mask);
 	its_send_int(dev2, 20);
 	wait_for_interrupts(&mask);
-	report(check_acked(&mask, -1, -1),
-			"dev2/eventid=20 still does not trigger any LPI");
+	before = check_acked(&mask, -1, -1);
+	report_xfail(under_tcg, before, "dev2/eventid=20 still may not trigger any LPI");
 
 	/* Now call the invall and check the LPI hits */
 	stats_reset();

@@ -750,8 +754,8 @@ static void test_its_trigger(void)
 	cpumask_set_cpu(3, &mask);
 	its_send_invall(col3);
 	wait_for_interrupts(&mask);
-	report(check_acked(&mask, 0, 8195),
-			"dev2/eventid=20 pending LPI is received");
+	after = check_acked(&mask, 0, 8195);
+	report(before != after, "dev2/eventid=20 pending LPI is
 	received");