Vitaly!
On Mon, 2 Nov 2015, Vitaly Kuznetsov wrote:
> Commit d32932d02e18 ("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.
Nice catch!
> Fixes: d32932d02e18 ("x86/irq: Convert IOAPIC to use hierarchical irqdomain
> interfaces")
> Signed-off-by: Vitaly Kuznetsov <[email protected]>
> ---
> arch/x86/include/asm/i8259.h | 1 +
> arch/x86/kernel/apic/vector.c | 3 +++
> arch/x86/kernel/i8259.c | 24 ++++++++++++++++--------
> 3 files changed, 20 insertions(+), 8 deletions(-)
>
> diff --git a/arch/x86/include/asm/i8259.h b/arch/x86/include/asm/i8259.h
> index ccffa53..bd55a77 100644
> --- a/arch/x86/include/asm/i8259.h
> +++ b/arch/x86/include/asm/i8259.h
> @@ -60,6 +60,7 @@ struct legacy_pic {
> void (*mask_all)(void);
> void (*restore_mask)(void);
> void (*init)(int auto_eoi);
> + void (*probe)(void);
> int (*irq_pending)(unsigned int irq);
> void (*make_irq)(unsigned int irq);
> };
> diff --git a/arch/x86/kernel/apic/vector.c b/arch/x86/kernel/apic/vector.c
> index 836d11b..aadd7ae 100644
> --- a/arch/x86/kernel/apic/vector.c
> +++ b/arch/x86/kernel/apic/vector.c
> @@ -361,6 +361,9 @@ int __init arch_probe_nr_irqs(void)
> if (nr < nr_irqs)
> nr_irqs = nr;
>
> + /* nr_legecy_irqs() depends on the PIC presence */
> + legacy_pic->probe();
> +
> return nr_legacy_irqs();
We can simplify this by letting probe() return the number of legacy
interrupts, hmm?
Thanks,
tglx
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