Mailing List Archive: [query] gic_set_lr always uses maintenance Interrupt

[query] gic_set_lr always uses maintenance Interrupt

Oct 30, 2013, 2:55 AM

Post #1 of 3 (3655 views)

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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Re: [query] gic_set_lr always uses maintenance Interrupt [ In reply to ]

mj.embd at gmail

Oct 31, 2013, 2:42 AM

Post #2 of 3 (3539 views)

Permalink

Hi Ian,

Can you please comment...

On Wed, Oct 30, 2013 at 3:25 PM, Mj Embd <mj.embd@gmail.com> wrote:
> 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 ?

--
-mj

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Re: [query] gic_set_lr always uses maintenance Interrupt [ In reply to ]

Ian.Campbell at citrix

Oct 31, 2013, 9:41 AM

Post #3 of 3 (3539 views)

Permalink

On Thu, 2013-10-31 at 15:12 +0530, Mj Embd wrote:
> Hi Ian,
>
> Can you please comment...

I think I commented on the version on xen-devel.

FYI xen-arm@ is for the discussion of the (mostly moribund) PV port of
Xen to ARM[0], discussion of the mainline port to ARM with virt
extensions[1] happens on xen-devel@. Yes, this is confusing.

Ian.

[0] http://wiki.xenproject.org/wiki/Xen_ARM_%28PV%29
[1] http://wiki.xenproject.org/wiki/Xen_ARM_with_Virtualization_Extensions

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