Re: [Xen-devel] [PATCH] arm64: xen: Implement EFI reset_system callback

[Julien Grall <julien.grall@xxxxxxx>]

Hi,

On 18/04/17 19:51, Juergen Gross wrote:
> On 18/04/17 20:46, Stefano Stabellini wrote:
> > On Tue, 18 Apr 2017, Juergen Gross wrote:
> > > On 18/04/17 20:37, Stefano Stabellini wrote:
> > > > On Thu, 6 Apr 2017, Juergen Gross wrote:
> > > > > On 06/04/17 18:43, Daniel Kiper wrote:
> > > > > > On Thu, Apr 06, 2017 at 06:22:44PM +0200, Juergen Gross wrote:
> > > > > > > On 06/04/17 18:06, Daniel Kiper wrote:
> > > > > > > > Hi Julien,
> > > > > > > >
> > > > > > > > On Thu, Apr 06, 2017 at 04:39:13PM +0100, Julien Grall wrote:
> > > > > > > > > Hi Daniel,
> > > > > > > > >
> > > > > > > > > On 06/04/17 16:20, Daniel Kiper wrote:
> > > > > > > > > > On Thu, Apr 06, 2017 at 04:38:24PM +0200, Juergen Gross wrote:
> > > > > > > > > > > On 06/04/17 16:27, Daniel Kiper wrote:
> > > > > > > > > > > > On Thu, Apr 06, 2017 at 09:32:32AM +0100, Julien Grall wrote:
> > > > > > > > > > > > > Hi Juergen,
> > > > > > > > > > > > >
> > > > > > > > > > > > > On 06/04/17 07:23, Juergen Gross wrote:
> > > > > > > > > > > > > > On 05/04/17 21:49, Boris Ostrovsky wrote:
> > > > > > > > > > > > > > > On 04/05/2017 02:14 PM, Julien Grall wrote:
> > > > > > > > > > > > > > > > The x86 code has theoritically a similar issue, altought EFI does not
> > > > > > > > > > > > > > > > seem to be the preferred method. I have left it unimplemented on x86 and
> > > > > > > > > > > > > > > > CCed Linux Xen x86 maintainers to know their view here.
> > > > > > > > > > > > > > > (+Daniel)
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > This could be a problem for x86 as well, at least theoretically.
> > > > > > > > > > > > > > > xen_machine_power_off() may call pm_power_off(), which is efi.reset_system.
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > So I think we should have a similar routine there.
> > > > > > > > > > > > > > +1
> > > > > > > > > > > > > >
> > > > > > > > > > > > > > I don't see any problem with such a routine added, in contrast to
> > > > > > > > > > > > > > potential "reboots" instead of power off without it.
> > > > > > > > > > > > > >
> > > > > > > > > > > > > > So I think this dummy xen_efi_reset_system() should be added to
> > > > > > > > > > > > > > drivers/xen/efi.c instead.
> > > > > > > > > > > > > I will resend the patch during day with xen_efi_reset_system moved
> > > > > > > > > > > > > to common code and implement the x86 counterpart (thought, I will
> > > > > > > > > > > > > not be able to test it).
> > > > > > > > > > > > I think that this is ARM specific issue. On x86 machine_restart() calls
> > > > > > > > > > > > xen_restart(). Hence, everything works. So, I think that it should be
> > > > > > > > > > > > fixed only for ARM. Anyway, please CC me when you send a patch.
> > > > > > > > > > > What about xen_machine_power_off() (as stated in Boris' mail)?
> > > > > > > > > > Guys what do you think about that:
> > > > > > > > > >
> > > > > > > > > > --- a/drivers/firmware/efi/reboot.c
> > > > > > > > > > +++ b/drivers/firmware/efi/reboot.c
> > > > > > > > > > @@ -55,7 +55,7 @@ static void efi_power_off(void)
> > > > > > > > > >
> > > > > > > > > > static int __init efi_shutdown_init(void)
> > > > > > > > > > {
> > > > > > > > > > -       if (!efi_enabled(EFI_RUNTIME_SERVICES))
> > > > > > > > > > +       if (!efi_enabled(EFI_RUNTIME_SERVICES) || efi_enabled(EFI_PARAVIRT))
> > > > > > > > > >                return -ENODEV;
> > > > > > > > > >
> > > > > > > > > >        if (efi_poweroff_required())
> > > > > > > > > >
> > > > > > > > > >
> > > > > > > > > > Julien, for ARM64 please take a look at 
> > > > > > > > > > arch/arm64/kernel/efi.c:efi_poweroff_required(void).
> > > > > > > > > >
> > > > > > > > > > I hope that tweaks for both files should solve our problem.
> > > > > > > > > This sounds good for power off (I haven't tried to power off DOM0
> > > > > > > > > yet). But this will not solve the restart problem (see
> > > > > > > > > machine_restart in arch/arm64/kernel/process.c) which call directly
> > > > > > > > > efi_reboot.
> > > > > > > > Hmmm... It seems to me that efi.reset_system override with empty function
> > > > > > > > in arch/arm/xen/efi.c is the best solution. So, I see three patches here.
> > > > > > > > One for drivers/firmware/efi/reboot.c, one for arch/arm/xen/efi.c and one
> > > > > > > > for arch/arm64/kernel/efi.c. Does it make sense?
> > > > > > > I still think the empty function should be in drivers/xen/efi.c and we
> > > > > > > should use it in arch/x86/xen/efi.c, too.
> > > > > > If you wish we can go that way too. Though I thing that we should fix
> > > > > > drivers/firmware/efi/reboot.c:efi_shutdown_init() too. Just in case.
> > > > > Sure, go ahead. I won't object.
> > > > For the Xen on ARM side, the original patch that started this thread
> > > > (20170405181417.15985-1-julien.grall@xxxxxxx) is good to go, right?
> > > As I said: the dummy xen_efi_reset_system() should be in
> > > drivers/xen/efi.c
> > OK. Who is working on it?
> Didn't Julien say he would do it?
Yes. I looked at bit closer to the problem mention with power off. 
xen_efi_reset_system cannot be a NOP because there may not be fallback 
alternatives (see machine_power_off in arch/arm64/kernel/process.c)
So I think we would have to translate EFI_RESET* to Xen SHUTDOWN_* and 
then call HYPERVISOR_sched_op directly.
I will send a new version soon.

Cheers,

--
Julien Grall

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
https://lists.xen.org/xen-devel