Re: [Xen-devel] [PATCH v3.1 09/15] xen/x86: allow the emulated APICs to be enabled for the hardware domain

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 04.11.16 at 10:47, <roger.pau@xxxxxxxxxx> wrote:
> On Fri, Nov 04, 2016 at 03:19:11AM -0600, Jan Beulich wrote:
>> >>> On 29.10.16 at 10:59, <roger.pau@xxxxxxxxxx> wrote:
>> > --- a/xen/arch/x86/domain.c
>> > +++ b/xen/arch/x86/domain.c
>> > @@ -509,6 +509,27 @@ void vcpu_destroy(struct vcpu *v)
>> >          xfree(v->arch.pv_vcpu.trap_ctxt);
>> >  }
>> >  
>> > +static bool emulation_flags_ok(const struct domain *d, uint32_t emflags)
>> > +{
>> > +
>> > +    if ( is_hvm_domain(d) )
>> > +    {
>> > +        if ( is_hardware_domain(d) &&
>> > +             emflags != 
>> > (XEN_X86_EMU_PIT|XEN_X86_EMU_LAPIC|XEN_X86_EMU_IOAPIC) )
>> > +            return false;
>> 
>> Why are hardware domains required to get all three?
> 
> The PIT is always enabled for hardware domains, although we might consider 
> disabling it for PVHv2 Dom0? TBH, I don't have a strong opinion here.

I think unless there's a reason to require it, it should be optional.

> The local APIC and IO APIC are required in order to deliver interrupts from 
> physical devices (this is only for PVHv2 hardware domains).

I can see the need for an LAPIC, but I don't think IO-APICs are
strictly necessary. Therefore I'd like the option of it being optional
at least to be considered (perhaps by way of a brief note in the
commit message).

Jan


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
https://lists.xen.org/xen-devel