linux-kernel - Re: EFI runtime-services on x86

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Message-ID: <20100802103535.6442ab49@feng-i7>
Date:	Mon, 2 Aug 2010 10:35:35 +0800
From:	Feng Tang <feng.tang@...el.com>
To:	Bjorn Helgaas <bjorn.helgaas@...com>
CC:	Matthew Garrett <mjg59@...f.ucam.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	<ying.huang@...el.com>
Subject: Re: EFI runtime-services on x86_64

Hi Bjorn,

On Sat, 31 Jul 2010 04:58:48 +0800
Bjorn Helgaas <bjorn.helgaas@...com> wrote:

> Hello Feng,
> 
> Can you educate me about your commit 772be899bc, "86: Make EFI RTC
> function depend on 32bit again"?
> 
> It adds "#ifdef CONFIG_X86_32" to avoid using efi_get_time() and
> efi_set_rtc_mmss(), but there's no explanation of *why* those services
> only work on 32-bit.
> 
> Is this an EFI spec limitation?  Do the other EFI runtime services
> work on 64-bit, since you didn't touch them?  Or do we just not use
> any of the others?
> 

Commit 772be899bc, "86: Make EFI RTC function depend on 32bit again" is
a regression fix for 7bd867d "x86: Move get/set_wallclock to x86_platform_ops".
These 2 commits just abstract the rtc service for legacy x86 PC/EFI/Virtualiation
kernel, and has no functional change to existing code.

I'm not familiar with EFI, but my understanding is current EFI code in 
kernel only provides the get/set_time service for x86_32 platform.

Cc Ying who is more familiar with EFI than me.

Thanks,
Feng
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