linux-kernel - Re: [PATCH v2 16/16] ARM64: XEN: Initialize Xen specific UEFI runtime services

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Date:	Mon, 18 Jan 2016 18:27:48 +0000
From:	Mark Rutland <mark.rutland@....com>
To:	Stefano Stabellini <stefano.stabellini@...citrix.com>
Cc:	Shannon Zhao <zhaoshenglong@...wei.com>, ard.biesheuvel@...aro.org,
	linux-arm-kernel@...ts.infradead.org,
	stefano.stabellini@...rix.com, david.vrabel@...rix.com,
	catalin.marinas@....com, will.deacon@....com,
	julien.grall@...rix.com, xen-devel@...ts.xen.org,
	devicetree@...r.kernel.org, linux-efi@...r.kernel.org,
	linux-kernel@...r.kernel.org, shannon.zhao@...aro.org,
	peter.huangpeng@...wei.com, Jan Beulich <JBeulich@...ell.com>,
	Ian Campbell <Ian.Campbell@...rix.com>
Subject: Re: [PATCH v2 16/16] ARM64: XEN: Initialize Xen specific UEFI
 runtime services

On Mon, Jan 18, 2016 at 05:45:24PM +0000, Stefano Stabellini wrote:
> On Mon, 18 Jan 2016, Mark Rutland wrote:
> > On Fri, Jan 15, 2016 at 02:55:29PM +0800, Shannon Zhao wrote:
> > > +void __init xen_efi_runtime_setup(void)
> > > +{
> > > +	efi.get_time                 = xen_efi_get_time;
> > > +	efi.set_time                 = xen_efi_set_time;
> > > +	efi.get_wakeup_time          = xen_efi_get_wakeup_time;
> > > +	efi.set_wakeup_time          = xen_efi_set_wakeup_time;
> > > +	efi.get_variable             = xen_efi_get_variable;
> > > +	efi.get_next_variable        = xen_efi_get_next_variable;
> > > +	efi.set_variable             = xen_efi_set_variable;
> > > +	efi.query_variable_info      = xen_efi_query_variable_info;
> > > +	efi.update_capsule           = xen_efi_update_capsule;
> > > +	efi.query_capsule_caps       = xen_efi_query_capsule_caps;
> > > +	efi.get_next_high_mono_count = xen_efi_get_next_high_mono_count;
> > > +	efi.reset_system             = NULL;
> > > +}
> > 
> > How do capsules work in the absence of an EFI system reset?
> 
> Actually I don't think that capsules are available in Xen on ARM64 yet,
> see "TODO - disabled until implemented on ARM" in
> xen/common/efi/runtime.c.
> 
> FYI system reset is available, but it is provided via a different
> mechanism (HYPERVISOR_sched_op(xen_restart...)

Will that trigger Xen to do the right thing to trigger capsule updates
when implemented in Xen? Or do we need a xen_efi_reset_system?

Does that override PSCI?

In machine_restart we try efi_reboot first specifically to allow for
capsule updates. Similarly drivers/firmware/efi/reboot.c registers
efi_power_off late in order to override anything else, though that's
best-effort at present.

Thanks,
Mark.