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Re: [Qemu-devel] [PATCH v3 06/13] pc: apic_common: extend APIC ID proper
From: |
Eduardo Habkost |
Subject: |
Re: [Qemu-devel] [PATCH v3 06/13] pc: apic_common: extend APIC ID property to 32bit |
Date: |
Tue, 18 Oct 2016 12:14:43 -0200 |
User-agent: |
Mutt/1.7.0 (2016-08-17) |
On Tue, Oct 18, 2016 at 04:01:56PM +0200, Igor Mammedov wrote:
> On Tue, 18 Oct 2016 10:59:17 -0200
> Eduardo Habkost <address@hidden> wrote:
>
> > On Tue, Oct 18, 2016 at 02:36:10PM +0200, Igor Mammedov wrote:
> > > On Tue, 18 Oct 2016 08:56:28 -0200
> > > Eduardo Habkost <address@hidden> wrote:
> > >
> > > > On Thu, Oct 13, 2016 at 11:52:40AM +0200, Igor Mammedov wrote:
> > > > > ACPI ID is 32 bit wide on CPUs with x2APIC support.
> > > > > Extend 'id' property to support it.
> > > > >
> > > > > Signed-off-by: Igor Mammedov <address@hidden>
> > > > > ---
> > > > > v3:
> > > > > keep original behaviour where 'id' is readonly after
> > > > > object is realized (pbonzini)
> > > > > ---
> > > > [...]
> > > > > diff --git a/hw/intc/apic_common.c b/hw/intc/apic_common.c
> > > > > index 8d01c9c..30f2af0 100644
> > > > > --- a/hw/intc/apic_common.c
> > > > > +++ b/hw/intc/apic_common.c
> > > > > @@ -428,7 +429,6 @@ static const VMStateDescription
> > > > > vmstate_apic_common = {
> > > > > };
> > > > >
> > > > > static Property apic_properties_common[] = {
> > > > > - DEFINE_PROP_UINT8("id", APICCommonState, id, -1),
> > > > > DEFINE_PROP_UINT8("version", APICCommonState, version, 0x14),
> > > > > DEFINE_PROP_BIT("vapic", APICCommonState, vapic_control,
> > > > > VAPIC_ENABLE_BIT,
> > > > > true),
> > > > > @@ -437,6 +437,49 @@ static Property apic_properties_common[] = {
> > > > > DEFINE_PROP_END_OF_LIST(),
> > > > > };
> > > > >
> > > > > +static void apic_common_get_id(Object *obj, Visitor *v, const char
> > > > > *name,
> > > > > + void *opaque, Error **errp)
> > > > > +{
> > > > > + APICCommonState *s = APIC_COMMON(obj);
> > > > > + int64_t value;
> > > > > +
> > > > > + value = s->apicbase & MSR_IA32_APICBASE_EXTD ?
> > > > > s->initial_apic_id : s->id;
> > > > > + visit_type_int(v, name, &value, errp);
> > > > > +}
> > > >
> > > > Who exactly is going to read this property and require this logic
> > > > to be in the property getter?
> > > As it's set/read only from CPU we don't actually have to expose it
> > > as property.
> > > However, I've kept it as read/write property because it has already
> > > been this way and been exposed to external users as some magic property.
> > > Not sure is anyone cares.
> > >
> > >
> > > > Do we really need to expose this to the outside as a magic
> > > > property that changes depending on hardware state? Returning
> > > > initial_apic_id sounds much simpler.
> > > Well that's what it is now, so I've kept current behavior.
> > > If we decide to change property behavior or drop it altogether
> > > I can do it on top.
> > >
> >
> > I agree to make them static properties as follow-up patch. This
> > way, if the change breaks anything we can revert only that patch.
> Static property won't work here as it should show APIC ID
> depending on current CPU mode.
My suggestion is to _not_ show a different ID depending on the
current mode, to keep it simple. We can just have
"initial-apic-id" and "id" properties.
But, anyway, I didn't mean to suggest static properties
specifically. Where I say "static property" above, please read
"simple property that returns just a simple struct field and
don't need custom getter/setter code". That means either using a
static property (in case we still want it to be writeable, which
I doubt) or using object_property_add_uint*_ptr().
>
> I could make it readonly property on respin,
> and set apic.id/initial_apic_id directly from CPU.
> Change would be
> - apic_common_set_id()
> + apic_common::set_apic_id() callback
> It won't get us less LOC, more likely it will take even more
> code to do so.
> As it's in this patch, it's at least consistent in a way
> values are get/set. And effectively it's readonly due to check:
Don't worry about doing it on the respin. I'm OK with keeping the
current version by now, and change it in a follow-up patch.
>
> + if (dev->realized) {
> + qdev_prop_set_after_realize(dev, name, errp);
> + return;
> + }
>
> as external user can see only realized apic device.
That's true. But we could avoid all the extra getter/setter code
if we just use a static property or a read-only
object_property_add_uint*_ptr() property.
(All I say above are suggestions for a follow-up patch. I'm OK
with keeping the existing behavior like you do in this patch, to
keep this series simple.)
--
Eduardo
[Qemu-devel] [PATCH v3 06/13] pc: apic_common: extend APIC ID property to 32bit, Igor Mammedov, 2016/10/13
[Qemu-devel] [PATCH v3 07/13] pc: apic_common: restore APIC ID to initial ID on reset, Igor Mammedov, 2016/10/13
[Qemu-devel] [PATCH v3 08/13] pc: apic_common: reset APIC ID to initial ID when switching into x2APIC mode, Igor Mammedov, 2016/10/13
[Qemu-devel] [PATCH v3 09/13] pc: kvm_apic: pass APIC ID depending on xAPIC/x2APIC mode, Igor Mammedov, 2016/10/13