Re: [PATCH v5 3/4] KVM: x86: Add EOI exit bitmap inference

[Jan Kiszka <jan.kiszka@siemens.com>]

On 2015-07-29 22:27, Steve Rutherford wrote:
> On Wed, Jul 29, 2015 at 02:38:09PM +0200, Paolo Bonzini wrote:
>>
>>
>> On 28/07/2015 01:17, Steve Rutherford wrote:
>>> diff --git a/arch/x86/kvm/ioapic.h b/arch/x86/kvm/ioapic.h
>>> index d8cc54b..f6ce112 100644
>>> --- a/arch/x86/kvm/ioapic.h
>>> +++ b/arch/x86/kvm/ioapic.h
>>> @@ -9,6 +9,7 @@ struct kvm;
>>>  struct kvm_vcpu;
>>>  
>>>  #define IOAPIC_NUM_PINS  KVM_IOAPIC_NUM_PINS
>>> +#define MAX_NR_RESERVED_IOAPIC_PINS 48
>>
>> Why is this needed?
> This constant is used to bound the number of IOAPIC pins that are
> reservable when enabling KVM_CAP_SPLIT_IRQCHIP. IIRC, x86 doesn't
> support more than 2 IOAPICs.  

Huh? Surely not. I've already seen boxes with at least three, and I
think you can even hot-plug them today via extension cards. Not saying
that QEMU supports that already, even without KVM, but we must not limit
ourselves in the kernel API.

So please remove such a static limit on how many IOAPICs userspace can
emulate or raise it to something sufficiently large that will last long
enough.

Jan

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