x86/irq: fix calculation of max PV dom0 pIRQs

The current calculation of PV dom0 pIRQs uses:

n = min(fls(num_present_cpus()), dom0_max_vcpus());

The usage of fls() is wrong, as num_present_cpus() already returns the number
of present CPUs, not the bitmap mask of CPUs.

Fix by removing the usage of fls().

Fixes: 7e73a6e7f1 ('have architectures specify the number of PIRQs a hardware domain gets')
Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>
master commit: 5c56361c61
master date: 2024-11-25 11:33:06 +0100

xen/arch/x86/io_apic.c

@@ -2727,7 +2727,7 @@ void __init ioapic_init(void)
 
 unsigned int __hwdom_init arch_hwdom_irqs(const struct domain *d)
 {
-    unsigned int n = fls(num_present_cpus());
+    unsigned int n = num_present_cpus();
     /* Bounding by the domain pirq EOI bitmap capacity. */
     const unsigned int max_irqs = min_t(unsigned int, nr_irqs,
                                         PAGE_SIZE * BITS_PER_BYTE);