Re: [rfc 4.16-rt patch] arm64: efi,fpsimd: use a local_lock() in efi_virtmap_load()

[Mike Galbraith <efault@gmx.de>]

On Thu, 2018-07-26 at 17:09 +0200, Sebastian Andrzej Siewior wrote:
> On 2018-07-11 17:07:22 [+0200], Mike Galbraith wrote:
> > Greetings,
> > 
> > With the patch below, there's still one neon splat to figure out what
> > to do with should this patch not die a gruesome death.  Cavium box
> > boots and seemingly works fine modulo kvm, which is utterly deadly in
> > 4.16-rt due to..
> > 
> > 972             if (!vgic_initialized(vcpu->kvm))
> > 973                     return false;
> > 974
> > 975             irq = vgic_get_irq(vcpu->kvm, vcpu, vintid);
> > 976             spin_lock_irqsave(&irq->irq_lock, flags);
> > 
> > ..that lock apparently having wandered into a minefield post v4.14.
> > 
> > Remaining neon splat:
> 
> I don't have this with preempt-disable patch for kernel_neon_begin()
> (posted seconds ago).

Oh, forget you _ever saw_ that patch.  It later demonstrated it's
"correctness" quite convincingly.  I didn't explicitly recall it due to
the patch it tried to build upon proving in the end to be a bit south
of wonderful itself, making the whole exercise a "let's make a bad
situation even worse" kinda thing :)

	-Mike