Re: [PATCH] MIPS: Fix broken malta qemu

[Guenter Roeck]

On 04/02/2016 05:19 AM, Qais Yousef wrote:
> Hi Paul,
>
> On 01/04/2016 13:48, Paul Burton wrote:
> > On Thu, Mar 17, 2016 at 09:08:09PM +0000, Qais Yousef wrote:
> > > Malta defconfig compiles with GIC on. Hence when compiling for SMP it causes the
> > > new IPI code to be activated. But on qemu malta there's no GIC causing a
> > > BUG_ON(!ipidomain) to be hit in mips_smp_ipi_init().
> > >
> > > Since in that configuration one can only run a single core SMP (!), skip IPI
> > > initialisation if we detect that this is the case. It is a sensible behaviour
> > > to introduce and should keep such possible configuration to run rather than die
> > > hard unnecessarily.
> > Hi Qais/Ralf,
> >
> > This patch is insufficient I'm afraid. It's entirely possible to use SMP
> > with multiple VPEs in a single core on Malta boards that don't have a
> > GIC - we have code handling IPIs in that case guarded by #ifdef
> > CONFIG_MIPS_MT_SMP in arch/mips/mti-malta/malta-int.c. I think the
> > BUG_ON needs to be removed entirely, unless that single-core multi-VPE
> > IPI code is also converted to use an IPI irqdomain.
>
> I was under the impression that SMP is only supported under GIC and older forms of SMP are deprecated.
>
> I think the problem you're describing is different to the one this is trying to fix. The right fix for your issue is to make CONFIG_GENERIC_IRQ_IPI selected when CONFIG_MIPS_GIC && !CONFIG_MIPS_MT_SMP.
Didn't Paul say that his system doesn't have a GIC ? Are you saying that he can not
(or no longer) run an image built for SMP on his system ?

Guenter