Re: [Minios-devel] [UNIKRAFT PATCHv4 38/43] plat/kvm: Implement shutdown for Arm64

[Wei Chen <Wei.Chen@xxxxxxx>]

Hi Julien,

> -----Original Message-----
> From: Julien Grall <julien.grall@xxxxxxx>
> Sent: 2018年7月19日 21:40
> To: Wei Chen <Wei.Chen@xxxxxxx>; minios-devel@xxxxxxxxxxxxxxxxxxxx;
> simon.kuenzer@xxxxxxxxx
> Cc: Kaly Xin <Kaly.Xin@xxxxxxx>; nd <nd@xxxxxxx>
> Subject: Re: [Minios-devel] [UNIKRAFT PATCHv4 38/43] plat/kvm: Implement
> shutdown for Arm64
> 
> Hi Wei,
> 
> On 06/07/18 10:03, Wei Chen wrote:
> > QEMU/KVM provide a PSCI interface for virtual machine on
> > Arm64 platform. So we use this interface to implement
> > platform system off function.
> >
> > Signed-off-by: Wei Chen <Wei.Chen@xxxxxxx>
> > ---
> >   plat/kvm/shutdown.c | 11 +++++++++--
> >   1 file changed, 9 insertions(+), 2 deletions(-)
> >
> > diff --git a/plat/kvm/shutdown.c b/plat/kvm/shutdown.c
> > index a513df9..0f0a01f 100644
> > --- a/plat/kvm/shutdown.c
> > +++ b/plat/kvm/shutdown.c
> > @@ -22,7 +22,8 @@
> >    */
> >
> >   #include <errno.h>
> > -#include <x86/cpu.h>
> > +#include <cpu.h>
> > +#include <irq.h>
> >   #include <uk/print.h>
> >   #include <uk/plat/bootstrap.h>
> >
> > @@ -38,7 +39,11 @@ void ukplat_terminate(enum ukplat_gstate request 
> > __unused)
> >      * be 83 ('S', 41 << 1 | 1).
> >      */
> >     uk_printk("Unikraft halted\n");
> > +#if defined(__X86_64__)
> >     outw(0x501, 41);
> > +#elif defined(__ARM_64__)
> > +   system_off();
> > +#endif
> >
> >     /*
> >      * If we got here, there is no way to initiate "shutdown" on virtio
> > @@ -49,7 +54,9 @@ void ukplat_terminate(enum ukplat_gstate request __unused)
> >
> >   static void cpu_halt(void)
> >   {
> > -   __asm__ __volatile__("cli; hlt");
> > +   local_irq_disable();
> > +   halt();
> 
> I think you want to move halt() in the for loop for Arm because WFI will
> come back when an interrupt is received. This means you will go into a
> busy loop wasting power.
> 

I think I don't want the WFI come back. The role of the cpu_halt is used
to hang up the system. It's not an idle.

> > +
> >     for (;;)
> >             ;
> >   }
> >
> 
> Cheers,
> 
> --
> Julien Grall
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