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Re: [Xen-devel] [PATCH RFC] efi: By default use the BOOT_ACPI method instead of BOOT_EFI unless on reduced ACPI hardware.

On Thu, Jan 22, 2015 at 09:49:08AM +0000, Jan Beulich wrote:
> >>> On 21.01.15 at 22:53, <konrad.wilk@xxxxxxxxxx> wrote:
> > This mimics the behavior of the Linux kernel in which the reboot
> > sequence by default under EFI booted kernels is first ACPI.
> Which is contrary to the EFI spec. I.e. NAK.

I am failing to see that in the spec. I see that it says what
the ResetSystem() call does, but nothing about "MUST".

I see this at the start of the spec:

" Together, these provide a standard environment for booting an OS. This
specification is designed as a pure interface specification. As such,
the specification defines the set of interface s and structures that
platform firmware must implement. "

(which talks about 'booting an OS' - which this is not, and interestingly
enough - it does say implement, but not where it must implement it

But I have not dug that deep in the spec to find something
that says you MUST not use existing other specs? Perhaps you
remember where the contrary part is?

Also, why do we want to be different that Windows and Linux when doing
EFI operations?

> > EFI reboot is only tried if the user supplied it or if the hardware
> > is an ACPI 5.0 (or higher) reduced hardware board.
> > 
> > This fixes the EFI firmware crashing on Lenovo ThinkCentre M57
> Buggy firmware should be worked around with "reboot="; I'd
> certainly accept a patch to bypass efi_reset_system() in that
> case.

Independent of the conversation above I will work the patch
that way.  Would you also be OK if I stuck the DMI data for the
ThinkCentre to make this automatic?

> Jan

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