Re: [Xen-devel] [PATCH v7 23/32] xen/x86: make sure the HVM callback vector is correctly set

[Roger Pau Monnà <roger.pau@xxxxxxxxxx>]

El 15/10/15 a les 13.30, Paul Durrant ha escrit:
>> -----Original Message-----
>> From: xen-devel-bounces@xxxxxxxxxxxxx [mailto:xen-devel-
>> bounces@xxxxxxxxxxxxx] On Behalf Of Andrew Cooper
>> Sent: 14 October 2015 17:02
>> To: Jan Beulich; Roger Pau Monne
>> Cc: xen-devel@xxxxxxxxxxxxxxxxxxxx
>> Subject: Re: [Xen-devel] [PATCH v7 23/32] xen/x86: make sure the HVM
>> callback vector is correctly set
>>
>> On 14/10/15 16:54, Jan Beulich wrote:
>>>>>> On 02.10.15 at 17:48, <roger.pau@xxxxxxxxxx> wrote:
>>>> --- a/xen/arch/x86/hvm/irq.c
>>>> +++ b/xen/arch/x86/hvm/irq.c
>>>> @@ -330,6 +330,10 @@ void hvm_set_callback_via(struct domain *d,
>> uint64_t
>>>> via)
>>>>           (via_type > HVMIRQ_callback_vector) )
>>>>          via_type = HVMIRQ_callback_none;
>>>>
>>>> +    if ( via_type != HVMIRQ_callback_vector &&
>>>> +         (!has_vlapic(d) || !has_vioapic(d) || !has_vpic(d)) )
>>>> +        return;
>>> Why are both IO-APIC and PIC required? Doesn't one suffice, or
>>> can't MSI-like interrupts even get delivered without either?
>>
>> In real hardware, MSI-like interrupts have no interaction with the
>> IO-APIC or PIC.
>>
>> In fact, the purpose of the IO-APIC is to turn legacy line interrupts
>> into MSI interrupts.  The PICs were from the pre-MSI days where it
>> asserted the #INTR pin on the processor.
>>
>> Our virtual interrupt infrastructure should behave in a consistent manor.
>>
> 
> IIRC both the intx and gsi variants of the callback via go in at the vioapic 
> level.

OK, so I can remove the PIC requirement.

Roger.


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