Re: [PATCH 4/5] x86/apic: Support 15 bits of APIC ID in IOAPIC/MSI where available

From: Thomas Gleixner
Date: Thu Oct 08 2020 - 07:54:59 EST


On Wed, Oct 07 2020 at 13:20, David Woodhouse wrote:
>
> + /*
> + * If the hypervisor supports extended destination ID in IOAPIC
> + * and MSI, that increases the maximum APIC ID that can be used
> + * for non-remapped IRQ domains.
> + */
> + if (x86_init.hyper.msi_ext_dest_id()) {
> + msi_ext_dest_id = 1;
> + apic_limit = 32767;
> + }

This needs to be outside of the remap mode check because?

> +
> if (remap_mode != IRQ_REMAP_X2APIC_MODE) {
> /*
> * Using X2APIC without IR is not architecturally supported
> @@ -1856,9 +1868,10 @@ static __init void try_to_enable_x2apic(int remap_mode)
> * in physical mode, and CPUs with an APIC ID that cannnot
> * be addressed must not be brought online.
> */
> - x2apic_set_max_apicid(255);
> + x2apic_set_max_apicid(apic_limit);
> x2apic_phys = 1;
> }
> +
> x2apic_enable();
> }
>
> diff --git a/arch/x86/kernel/apic/msi.c b/arch/x86/kernel/apic/msi.c
> index 2825e003259c..85206f971284 100644
> --- a/arch/x86/kernel/apic/msi.c
> +++ b/arch/x86/kernel/apic/msi.c
> @@ -23,8 +23,11 @@
>
> struct irq_domain *x86_pci_msi_default_domain __ro_after_init;
>
> +int msi_ext_dest_id __ro_after_init;

bool please.

Aside of that this breaks the build for a kernel with CONFIG_PCI_MSI=n

Thanks,

tglx