Re: [PATCH] xen/arm: acpi: Support memory reserve configuration table

[Marc Zyngier <maz@xxxxxxxxxx>]

On Tue, 06 Sep 2022 03:52:37 +0100,
Leo Yan <leo.yan@xxxxxxxxxx> wrote:
> 
> On Thu, Aug 25, 2022 at 10:40:41PM +0800, Leo Yan wrote:
> 
> [...]
> 
> > > > But here I still cannot create the concept that how GIC RD tables play
> > > > roles to support the para virtualization or passthrough mode.
> > >
> > > I am not sure what you are actually asking. The pending tables are just
> > > memory you give to the GICv3 to record the state of the interrupts.
> >
> > For more specific, Xen has its own RD pending table, and we can use
> > this pending table to set state for SGI/PPI/LPI for a specific CPU
> > interface.  Xen works as hypervisor, it saves and restores the pending
> > table according to switched in VM context, right?
> >
> > On the other hand, what's the purpose for Linux kernel's GIC RD
> > pending table?  Is it only used for nested virtulisation?  I mean if
> > Linux kernel's GIC RD pending table is not used for the drivers in
> > Dom0 or DomU, then it's useless to pass it from the primary kernel to
> > secondary kernel; as result, we don't need to reserve the persistent
> > memory for the pending table in this case.
> 
> I don't receive further confirmation from Marc, anyway, I tried to cook
> a kernel patch to mute the kernel oops [1].

What sort of confirmation do you expect from me? None of what you
write above make much sense in the face of the architecture.

> Hope this is not too arbitrary and we can move forward a bit.
> 
> Thanks,
> Leo
> 
> [1] 
> https://lore.kernel.org/lkml/20220906024040.503764-1-leo.yan@xxxxxxxxxx/T/#u

I'm totally baffled by the fact you're trying to add some extra hacks
to Linux just to paper over some of the Xen's own issues.

        M.

-- 
Without deviation from the norm, progress is not possible.