[PATCH 7/8] arm64/kexec: Add checks for KVM

[Geoff Levand]

Hi Takahiro,

On Mon, 2015-02-02 at 17:18 +0900, AKASHI Takahiro wrote:
> On 01/31/2015 04:48 AM, Geoff Levand wrote:
> > As an initial implementation we can hook into the CPU_DYING_FROZEN
> > notifier sent to hyp_init_cpu_notify().  The longer term solution
> > should use kvm_arch_hardware_enable() and kvm_arch_hardware_disable().
> 
> Are these two different approaches? 

Yes, these are two different solutions,  One initial work-around, and a
more involved proper solution.  Hooking into the CPU_DYING_FROZEN
notifier would be a initial fix.  The proper solution would be to move
the KVM setup to kvm_arch_hardware_enable(), and the shutdown to
kvm_arch_hardware_disable().


> kernel_exec() -> machine_shutdown() -> disable_nonboot_cpu()
>     -> _cpu_down() -> cpu_notify_nofail(CPU_DEAD|...)
> 
> On the other hand, kvm already has a hook into kvm_arch_hardware_disable():
>    (ignoring kvm_usage_count here)
> kvm_cpu_hotplug(CPU_DYING) -> hardware_disable()
>     -> hardware_disable_nolock() -> kvm_arch_hardware_disable()
> 
> So it seems that we don't have to add a new hook at hyp_init_cpu_notify()
> if kvm_arch_hardware_disable() is properly implemented.

Yes, that is correct.  But, as above, you would also need to update the
KVM startup to use kvm_arch_hardware_enable().

> disable_nonboot_cpu() will not inovke cpu hotplug on *boot* cpu, and
> we should handle it in a separate way though.

IIRC, the secondary cpus go through PSCI on shutdown, and that path
is working OK.  Maybe I am mistaken though.

The primary cpu shutdown (hyp stubs restored) is what is missing.  The
primary cpu goes through cpu_soft_restart(), and that is what is
currently failing.

-Geoff