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Re: [PATCH v4 for 4.23] Add GIC SGI boot/self tests in Xen
- To: "Grall, Julien" <julien@xxxxxxx>, Ayan Kumar Halder <ayan.kumar.halder@xxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- From: "Halder, Ayan Kumar" <ayankuma@xxxxxxx>
- Date: Thu, 17 Sep 2026 13:13:50 +0100
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- Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>, Bertrand Marquis <bertrand.marquis@xxxxxxx>, Michal Orzel <michal.orzel@xxxxxxx>, "Volodymyr Babchuk" <Volodymyr_Babchuk@xxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Anthony PERARD <anthony.perard@xxxxxxxxxx>, "Jan Beulich" <jbeulich@xxxxxxxx>, Roger Pau Monne <roger@xxxxxxxxxxxxxx>, "Doug Goldstein" <cardoe@xxxxxxxxxx>
- Delivery-date: Thu, 17 Sep 2026 12:14:28 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 17/09/2026 08:57, Grall, Julien wrote:
Hi Ayan,
Hi Julien,
On 16/09/2026 12:35, Ayan Kumar Halder wrote:
+static void __init expect_sgi(const cpumask_t *mask,
+ const unsigned int *before, const char
*what)
+{
+ s_time_t deadline = NOW() + MILLISECS(100);
+ unsigned int cpu;
+
+ for_each_cpu ( cpu, mask )
+ {
+ while ( sgi_count(cpu) == before[cpu] )
+ {
+ if ( NOW() > deadline )
+ panic("GIC selftest: %s: CPU%u did not receive
GIC_SGI_TEST\n",
+ what, cpu);
+ cpu_relax();
+ }
+ }
+
+ printk("GIC selftest: CPU%u: %s: OK\n", smp_processor_id(), what);
+}
+
+/*
+ * "All but self" is only meaningful once every CPU can take an SGI,
so it is
+ * run by whichever CPU observes that it is the last one to get here.
+ */
+static int __init gic_sgi_selftest(void)
+{
+ static atomic_t __initdata seen = ATOMIC_INIT(0);
+ unsigned int before[NR_CPUS] = { };
Sorry I didn't spot this earlier. NR_CPUS can be quite large (up to
16K). So this will blow up the stack.
As this is a test, we have hardcoded NR_CPUS = 4 in
automation/scripts/qemu-boot-selftest-arm64.sh.
If there are 16K CPUs, our test only checks for 4 cpus only.
However if there is still a concern ....
There are two options:
1) Use static
2) Temporarily allocate "before"
I don't have a strong opinion on which way to go with.
I can use static.
- Ayan
Cheers,
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