Messages in this thread | | | From | Michael Kelley <> | Subject | RE: [PATCH V4 2/3] HYPERV/IOMMU: Add Hyper-V stub IOMMU driver | Date | Thu, 21 Feb 2019 17:27:37 +0000 |
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From: lantianyu1986@gmail.com <lantianyu1986@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
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