Messages in this thread | | | Date | Tue, 12 Apr 2016 14:14:39 -0700 (PDT) | From | Stefano Stabellini <> | Subject | Re: Xen regression, Was: [PATCH] x86/irq: Probe for PIC presence before allocating descs for legacy IRQs |
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On Tue, 12 Apr 2016, Boris Ostrovsky wrote: > On 04/12/2016 02:06 PM, Stefano Stabellini wrote: > > On Tue, 12 Apr 2016, Boris Ostrovsky wrote: > > > On 04/11/2016 10:08 PM, Stefano Stabellini wrote: > > > > Hi all, > > > > > > > > Unfortunately this patch (now commit > > > > 8c058b0b9c34d8c8d7912880956543769323e2d8) causes a regression on Xen > > > > when running on top of QEMU: the number of PIT irqs get set to 0 by > > > > probe_8259A but actually there are 16. > > > > > > > > Any suggestions on how to fix this? > > > > > > > > 1) we could revert 8c058b0b9c34d8c8d7912880956543769323e2d8 > > > > 2) we could introduce an 'if (!xen_domain())' in probe_8259A > > > > 3) suggestions welcome > > > Stefano, do you have b4ff8389ed14b849354b59ce9b360bdefcdbf99c ? > > > > > > It was supposed to fix this problem for Xen. However, I just noticed that > > > arch/arm64/include/asm/irq.h makes nr_legacy_irqs() return 0 (unlike > > > arch/arm/include/asm/irq.h). Could that be the problem? > > I have b4ff8389ed14b849354b59ce9b360bdefcdbf99c but it doesn't fix the > > issue for me. > > > > Is the idea of your patch that xen_allocate_irq_gsi will allocate the > > descriptor dynamically instead? > > Right. > > > If so, it doesn't work because it > > doesn't get called for irq 14: > > So how has it worked until now then?
It didn't for me :-) Maybe it was working for DomUs, but not for Dom0?
> > piix_init_one -> ata_pci_sff_activate_host -> devm_request_irq -> > > devm_request_threaded_irq-> request_threaded_irq -> irq_to_desc(14) -> > > -EVAIL > > > > If you look at pci_xen_initial_domain, the loop: > > > > for (irq = 0; irq < nr_legacy_irqs(); irq++) { > > > > won't work anymore because by the time is called, nr_legacy_irqs() > > already returns 0, because it has been changed by probe_8259A(). > > > > We also need the following patch: > > > > --- > > > > xen/x86: actually allocate legacy interrupts on PV guests > > > > b4ff8389ed14 is incomplete: relies on nr_legacy_irqs() to get the number > > of legacy interrupts when actually nr_legacy_irqs() returns 0 after > > probe_8259A(). Use NR_IRQS_LEGACY instead. > > > > Signed-off-by: Stefano Stabellini <sstabellini@kernel.org> > > > > diff --git a/arch/x86/pci/xen.c b/arch/x86/pci/xen.c > > index beac4df..6db0060 100644 > > --- a/arch/x86/pci/xen.c > > +++ b/arch/x86/pci/xen.c > > @@ -492,7 +492,7 @@ int __init pci_xen_initial_domain(void) > > __acpi_register_gsi = acpi_register_gsi_xen; > > __acpi_unregister_gsi = NULL; > > /* Pre-allocate legacy irqs */ > > - for (irq = 0; irq < nr_legacy_irqs(); irq++) { > > + for (irq = 0; irq < NR_IRQS_LEGACY; irq++) { > > int trigger, polarity; > > if (acpi_get_override_irq(irq, &trigger, &polarity) == -1) > > > Won't we need the same change in the 'if (0 == nr_ioapics)' clause?
That's not a problem: there is 1 ioapic in my system and is detected correctly.
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