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

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Date:   Thu, 08 Oct 2020 14:02:48 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     David Woodhouse <dwmw2@...radead.org>, x86@...nel.org
Cc:     kvm <kvm@...r.kernel.org>, Paolo Bonzini <pbonzini@...hat.com>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 4/5] x86/apic: Support 15 bits of APIC ID in IOAPIC/MSI where available

On Thu, Oct 08 2020 at 13:54, Thomas Gleixner wrote:
> On Wed, Oct 07 2020 at 13:20, David Woodhouse wrote:
>> 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

So this wants to be

bool virt_ext_dest_id __ro_after_init;

in apic.c and then please make the IO/APIC places depend on this as well
so any change to the utilization of the reserved IO/APIC bits in the
future is not going to end up in surprises.

Thanks,

        tglx