• Vitaly Kuznetsov's avatar
    x86/irq: Probe for PIC presence before allocating descs for legacy IRQs · 8c058b0b
    Vitaly Kuznetsov authored
    Commit d32932d0 ("x86/irq: Convert IOAPIC to use hierarchical irqdomain
    interfaces") brought a regression for Hyper-V Gen2 instances. These
    instances don't have i8259 legacy PIC but they use legacy IRQs for serial
    port, rtc, and acpi. With this commit included we end up with these IRQs
    not initialized. Earlier, there was a special workaround for legacy IRQs
    in mp_map_pin_to_irq() doing mp_irqdomain_map() without looking at
    nr_legacy_irqs() and now we fail in __irq_domain_alloc_irqs() when
    irq_domain_alloc_descs() returns -EEXIST.
    
    The essence of the issue seems to be that early_irq_init() calls
    arch_probe_nr_irqs() to figure out the number of legacy IRQs before
    we probe for i8259 and gets 16. Later when init_8259A() is called we switch
    to NULL legacy PIC and nr_legacy_irqs() starts to return 0 but we already
    have 16 descs allocated.
    
    Solve the issue by separating i8259 probe from init and calling it in
    arch_probe_nr_irqs() before we actually use nr_legacy_irqs() information.
    
    Fixes: d32932d0 ("x86/irq: Convert IOAPIC to use hierarchical irqdomain interfaces")
    Signed-off-by: default avatarVitaly Kuznetsov <vkuznets@redhat.com>
    Cc: Jiang Liu <jiang.liu@linux.intel.com>
    Cc: K. Y. Srinivasan <kys@microsoft.com>
    Cc: stable@vger.kernel.org
    Link: http://lkml.kernel.org/r/1446543614-3621-1-git-send-email-vkuznets@redhat.comSigned-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
    8c058b0b
i8259.h 1.79 KB