Messages in this thread Patch in this message | | | Date | Thu, 21 Apr 2016 10:30:13 +0100 (BST) | From | Stefano Stabellini <> | Subject | Re: [PATCH] xen/x86: actually allocate legacy interrupts on PV guests |
| |
On Thu, 21 Apr 2016, Juergen Gross wrote: > On 20/04/16 15:15, Stefano Stabellini wrote: > > 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. > > Would you mind describing the resulting problem?
This is a good question. The symptom is:
ata_piix: probe of 0000:00:01.1 failed with error -22
> With this commit message I'm absolutely not capable to decide whether > e.g. the other use of nr_legacy_irqs() in pci_xen_initial_domain() is > correct or not.
I looked at it but I couldn't really test that code because if I try to change the number of ioapics in the system using the "noapic" command line option (which actually changes the number if ioapics, not lapics), I get an error from Linux saying that noapic is not supported when running on Xen.
In my opinion having nr_legacy_irqs() calls in Xen code, which returns 0, is like playing with fire. I think it would be safer/saner to replace them all with NR_IRQS_LEGACY, simply because reading the code one would not expect that all those loops don't actually have any iterations.
However I didn't make the change because I couldn't test it properly.
> > Signed-off-by: Stefano Stabellini <sstabellini@kernel.org> > > > > diff --git a/arch/x86/pci/xen.c b/arch/x86/pci/xen.c > > index beac4df..349b8ce 100644 > > --- a/arch/x86/pci/xen.c > > +++ b/arch/x86/pci/xen.c > > @@ -491,8 +491,11 @@ int __init pci_xen_initial_domain(void) > > #endif > > __acpi_register_gsi = acpi_register_gsi_xen; > > __acpi_unregister_gsi = NULL; > > - /* Pre-allocate legacy irqs */ > > - for (irq = 0; irq < nr_legacy_irqs(); irq++) { > > + /* > > + * Pre-allocate the legacy IRQs. Use NR_LEGACY_IRQS here > > + * because we don't have a PIC and thus nr_legacy_irqs() is zero. > > + */ > > + for (irq = 0; irq < NR_IRQS_LEGACY; irq++) { > > int trigger, polarity; > > > > if (acpi_get_override_irq(irq, &trigger, &polarity) == -1) > > >
| |