linux-kernel - Re: [PATCH -mm] kexec jump -v9

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Date:	Fri, 16 May 2008 10:08:06 +0800
From:	"Huang, Ying" <ying.huang@...el.com>
To:	Vivek Goyal <vgoyal@...hat.com>
CC:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Pavel Machek <pavel@....cz>, nigel@...el.suspend2.net,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-pm@...ts.linux-foundation.org,
	Kexec Mailing List <kexec@...ts.infradead.org>
Subject: Re: [PATCH -mm] kexec jump -v9

On Thu, 2008-05-15 at 21:51 -0400, Vivek Goyal wrote:
> On Fri, May 16, 2008 at 09:48:34AM +0800, Huang, Ying wrote:
> > On Thu, 2008-05-15 at 16:09 -0400, Vivek Goyal wrote:
> > [...]
> > > Ok, You want to make BIOS calls. We already do that using vm86 mode and
> > > use bios real mode interrupts. So why do we need this interface? Or, IOW,
> > > how is this interface better?
> > 
> > It can call code in 32-bit physical mode in addition to real mode. So It
> > can be used to call EFI runtime service, especially call EFI 64 runtime
> > service under 32-bit kernel or vice versa.
> > 
> > The main purpose of kexec jump is for hibernation. But I think if the
> > effort is small, why not support general 32-bit physical mode code call
> > at same time.
> > 
> 
> In general what's the environment requirements for EFI runtime 
> services? I mean, just that processor should be in protected mode with
> paging disabled or one need to stop all other cpus and devices and then make
> the call (as we are doing in this case?). 

Put processor in protected mode with paging disabled is sufficient. In
one of previous kexec jump versions, I provide some option to choose the
state saved (whether stop other cpus, whether stop devices).

I agree that now we should focus on kexec based hibernation. But I think
it is reasonable to keep the possibility with minimal effort.

Best Regards,
Huang Ying

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