linux-kernel - Re: [PATCH] efi/libstub/fdt: Standardize the names of EFI stub parameters

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Date:	Fri, 11 Sep 2015 14:46:43 +0200
From:	Daniel Kiper <daniel.kiper@...cle.com>
To:	Mark Rutland <mark.rutland@....com>
Cc:	Stefano Stabellini <stefano.stabellini@...citrix.com>,
	Shannon Zhao <zhaoshenglong@...wei.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>,
	"Ian.Campbell@...rix.com" <Ian.Campbell@...rix.com>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	"ard.biesheuvel@...aro.org" <ard.biesheuvel@...aro.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"leif.lindholm@...aro.org" <leif.lindholm@...aro.org>,
	"xen-devel@...ts.xen.org" <xen-devel@...ts.xen.org>,
	"julien.grall@...rix.com" <julien.grall@...rix.com>,
	"freebsd-arm@...ebsd.org" <freebsd-arm@...ebsd.org>,
	"matt.fleming@...el.com" <matt.fleming@...el.com>,
	"christoffer.dall@...aro.org" <christoffer.dall@...aro.org>,
	"jbeulich@...e.com" <jbeulich@...e.com>,
	"peter.huangpeng@...wei.com" <peter.huangpeng@...wei.com>,
	"shannon.zhao@...aro.org" <shannon.zhao@...aro.org>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Subject: Re: [PATCH] efi/libstub/fdt: Standardize the names of EFI stub
 parameters

On Thu, Sep 10, 2015 at 05:23:02PM +0100, Mark Rutland wrote:
> > > C) When you could go:
> > >
> > >    DT -> Discover Xen -> Xen-specific stuff -> Xen-specific EFI/ACPI discovery
> >
> > I take you mean discovering Xen with the usual Xen hypervisor node on
> > device tree. I think that C) is a good option actually. I like it. Not
> > sure why we didn't think about this earlier. Is there anything EFI or
> > ACPI which is needed before Xen support is discovered by
> > arch/arm64/kernel/setup.c:setup_arch -> xen_early_init()?
>
> Currently lots (including the memory map). With the stuff to support
> SPCR, the ACPI discovery would be moved before xen_early_init().
>
> > If not, we could just go for this. A lot of complexity would go away.
>
> I suspect this would still be fairly complex, but would at least prevent
> the Xen-specific EFI handling from adversely affecting the native case.
>
> > > D) If you want to be generic:
> > >    EFI -> EFI application -> EFI tables -> ACPI tables -> Xen-specific stuff
> > >           \------------------------------------------/
> > > 	   (virtualize these, provide shims to Dom0, but handle
> > > 	    everything in Xen itself)
> >
> > I think that this is good in theory but could turn out to be a lot of
> > work in practice. We could probably virtualize the RuntimeServices but
> > the BootServices are troublesome.
>
> What's troublesome with the boot services?
>
> What can't be simulated?

How do you want to access bare metal EFI boot services from dom0 if they
were shutdown long time ago before loading dom0 image? What do you need
from EFI boot services in dom0?

Daniel
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