From: lantianyu1...@gmail.com <lantianyu1...@gmail.com> Sent: Monday, February 11, 2019 6:20 AM > + /* > + * Hyper-V doesn't provide irq remapping function for > + * IO-APIC and so IO-APIC only accepts 8-bit APIC ID. > + * Cpu's APIC ID is read from ACPI MADT table and APIC IDs > + * in the MADT table on Hyper-v are sorted monotonic increasingly. > + * APIC ID reflects cpu topology. There maybe some APIC ID > + * gaps when cpu number in a socket is not power of two. Prepare > + * max cpu affinity for IOAPIC irqs. Scan cpu 0-255 and set cpu > + * into ioapic_max_cpumask if its APIC ID is less than 256. > + */ > + for (i = min_t(unsigned int, num_possible_cpus(), 255); i >= 0; i--)
The above isn't quite right. For example, if num_possible_cpus() is 8, then the loop will be executed 9 times, for values 8 down through 0. It should be executed for values 7 down through 0. > + if (cpu_physical_id(i) < 256) > + cpumask_set_cpu(i, &ioapic_max_cpumask); > + > + return 0; > +} Michael
