Re: [PATCH] x86/APIC: Remove x2APIC pure cluster mode

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Tue, Sep 24, 2024 at 04:27:36PM +0100, Andrew Cooper wrote:
> On 24/09/2024 4:10 pm, Roger Pau Monné wrote:
> > On Mon, Sep 23, 2024 at 03:35:59PM +0100, Matthew Barnes wrote:
> >> With the introduction of mixed x2APIC mode (using cluster addressing for
> >> IPIs and physical for external interrupts) the use of pure cluster mode
> >> doesn't have any benefit.
> >>
> >> Remove the mode itself, leaving only the code required for logical
> >> addressing when sending IPIs.
> >>
> >> Implements: https://gitlab.com/xen-project/xen/-/issues/189
> 
> We use the Resolves: tag for this.  Can fix on commit.
> 
> > There's at least one extra bit which I would also like to see removed,
> > either in this patch, or as following patch.
> >
> > In struct arch_irq_desc we have 3 cpumasks: cpu_mask, old_cpu_mask and
> > pending_mask.  After dropping cluster mode for external interrupts,
> > those fields could become integers AFACT, as now interrupts can only
> > target a single CPU opposed to a logical CPU set.
> 
> A separate patch for sure, but that sounds like a great improvement.

Oh, there are quite some fields of struct genapic that are not needed
anymore, since both implementations set it to the same function.  It
would be helpful to prune them.

Thanks, Roger.