Re: [Xen-devel] [PATCH 51/57] ARM: new VGIC: Add preliminary stub implementation

[Julien Grall <julien.grall@xxxxxxx>]

Hi,

On 03/13/2018 03:55 PM, Andre Przywara wrote:
> Hi,
>
> On 09/03/18 18:18, Julien Grall wrote:
> > Hi Andre,
> >
> > On 05/03/18 16:04, Andre Przywara wrote:
> > > The ARM arch code requires an interrupt controller emulation to implement
> > > vgic_clear_pending_irqs(), although it is suspected that it is actually
> > > not necessary. Go with a stub for now to make the linker happy.
> > The implementation of that function is fundamentally wrong on the
> > current vGIC for a few reasons:
> >      - lr_mask is reset but the LRs are not. This means when we context
> > switch back, the LR might still be written and injecting unexpected
> > interrupt (whoops).
> >      - both lists (inflight and pending) are cleared which means that a
> > physical interrupt pending on that vCPU is lost forever (stay active in
> > the physical so never going to fire again).
> >
> > Furthermore, I don't think that Xen business to reset the GIC on cpu_on.
> > If anything should be done, then is it on CPU_off to migrate the current
> > interrupts to another vCPU. But IIRC the OS is responsible for that.
> >
> > So I would kill that function. Any opinions?
> So I guess given that the patch is pretty small, we are good with
> keeping that for now, and solve this together with the old VGIC later.
I am ok with that.

Cheers,

--
Julien Grall

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