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

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Date:	Mon, 02 Aug 2010 10:42:00 +0800
From:	Huang Ying <ying.huang@...el.com>
To:	"Tang, Feng" <feng.tang@...el.com>
Cc:	Bjorn Helgaas <bjorn.helgaas@...com>,
	Matthew Garrett <mjg59@...f.ucam.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: EFI runtime-services on x86_64

Hi, Bjorn,

On Mon, 2010-08-02 at 10:35 +0800, Tang, Feng wrote:
> 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.

I think get/set_time service should have worked on x86_64 too. Just
lacks proper debugging/testing for recent kernels.

Best Regards,
Huang Ying

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