Re: [Patch][RFC] fix PAL_HALT ( is Re: [Xen-ia64-devel] [RFC] dump core is failed for PAL_HALT)

[Isaku Yamahata <yamahata@xxxxxxxxxxxxx>]

On Wed, Jan 24, 2007 at 11:43:37AM +0900, Akio Takebe wrote:
Content-Description: Mail message body

> Thank you for your suggestion.
> >Choice C.
> >     Modify PAL_HALT emulation as follows.
> >     If other vcpu is left and alive, vcpu is put in sleep.
> >     If current is the last vcpu, call domain_shutdown(SHUTDOWN_poweroff).
> >     It will be guaranteed that the vcpu which call panic() calls
> >        HYPERVISOR_shutdown(SHUTDOWN_crash) via xen_panic_block so that
> >        the guest domain's core dump should be created.
> >        (I haven't tested it though.)
> >
> >-- 
> 
> I make the patch of choice C.
> This patch modify PAL_HALT of guest domain.
> I can dump correctly with my patch.
> But if I use this patch, I cannot shutdown domU,
> because linux machine_halt() call cpu_halt from only one cpu.
> Do anyone know why linux call it from only one cpu?
> Or do I have miss-reading about that?

According to SDM vol2 11.9, PAL_HALT places cpu in low power state.
So the current behaviour that xen/ia64 shutdown unconditionally is
wrong.
CPU hot-unplug routine also calls cpu_halt(). In that case, 
only the targeted cpu should be halted. We don't want domain shutdown.

Probably modifying machine_reboot() and machine_power_off() 
needs modification(paravirtualization) to call shutdown hypercall.
-- 
yamahata

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