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[XenARM] [query] gic_set_lr always uses maintenance Interrupt


  • To: xen-arm@xxxxxxxxxxxxx
  • From: Mj Embd <mj.embd@xxxxxxxxx>
  • Date: Wed, 30 Oct 2013 15:25:44 +0530
  • Delivery-date: Wed, 30 Oct 2013 09:55:52 +0000
  • List-id: List for Xen ARM developers and users <xen-arm.lists.xen.org>

Hi,

As per section 5.2.2 of IHI0048B_b_gic_architecture_specification, If
hypervisor is injecting a VIRQ into guest, that is actually a HW IRQ,
and guest does EOI (provided conditions) the maintenance interrupt is
not needed.

In xen arch/arm/gic.c always while setting an LR using gic_set_lr ,
the maintenance_int is enabled.

Can some one clear the doubt on why it is done
a) is this because EOI by guest would result in control back to
hypervisor to replenish the LR for   inflight, as there is otherwise
no way to know in hypervisor that the LR is available.
or
b) some other reason ?

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