Re: [PATCH v4 35/49] KVM: arm64: GICv3: nv: Plug L1 LR sync into deactivation primitive

[Marc Zyngier <maz@kernel.org>]

[+ Darren]

On Tue, 31 Mar 2026 10:42:57 +0100,
Marc Zyngier <maz@kernel.org> wrote:
> 
> On Tue, 31 Mar 2026 07:31:54 +0100,
> Vishnu Pajjuri <vishnu@os.amperecomputing.com> wrote:
> > 
> > >> LOG:
> > >> [  164.647367] Call trace:
> > >> [  164.647368]  smp_call_function_many_cond+0x334/0x7a0 (P)
> > >> [  164.647372]  smp_call_function_many+0x20/0x40
> > >> [  164.647374]  kvm_make_all_cpus_request+0xec/0x1b8
> > >> [  164.647377]  vgic_queue_irq_unlock+0x1c8/0x2c8
> > >> [  164.647380]  kvm_vgic_inject_irq+0x194/0x1e0
> > >> [  164.647381]  kvm_vm_ioctl_irq_line+0x170/0x400
> > >> [  164.647386]  kvm_vm_ioctl+0x7b8/0xc88
> > >> [  164.647389]  __arm64_sys_ioctl+0xb4/0x118
> > >> [  164.647393]  invoke_syscall+0x6c/0x100
> > >> [  164.647397]  el0_svc_common.constprop.0+0x48/0xf0
> > >> [  164.647398]  do_el0_svc+0x24/0x38
> > >> [  164.647400]  el0_svc+0x3c/0x170
> > >> [  164.647403]  el0t_64_sync_handler+0xa0/0xe8
> > >> [  164.647405]  el0t_64_sync+0x1b0/0x1b8
> > > 
> > > This trace is about interrupt injection from userspace, not
> > > deactivation of a HW interrupt.
> > > None of that makes much sense.
> > 
> > Although this behavior is puzzling, it matches the trace I typically
> > observe on L0. After reverting the patch, I was able to boot L2 guests
> > successfully.
> 
> Well, this patch fixes real bugs, so it isn't going anywhere.
> 
> The patch you are reverting addresses the deactivation of a HW
> interrupt, which is likely to be a timer (that's the only one we
> support). The stacktrace points to the userspace injection of an SPI.
> 
> If we need to broadcast IPI, that's because there is no other SPI
> currently in flight. But if a CPU is not responding to the IPI, what
> is it doing? How does this interact with the patch you are reverting?
> 
> Given that I don't know what you're running, how you are running it,
> that I don't have access to whatever HW you are using, and that you
> are providing no useful information that'd help me debug this, I will
> leave it up to you to debug it and come back with a detailed analysis
> of the problem.

Have you made progress on this? I can't reproduce it at all despite my
best effort. I'm perfectly happy to help, but you need to give me
*something* to go on.

Thanks,

	M.

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