linux-kernel - Re: [PATCH] export efi.flags to sysfs

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Message-ID: <20140529124520.GC14570@redhat.com>
Date:	Thu, 29 May 2014 08:45:20 -0400
From:	Vivek Goyal <vgoyal@...hat.com>
To:	Dave Young <dyoung@...hat.com>
Cc:	matt.fleming@...el.com, bp@...en8.de, linux-kernel@...r.kernel.org,
	linux-efi@...r.kernel.org
Subject: Re: [PATCH] export efi.flags to sysfs

On Thu, May 29, 2014 at 10:08:37AM +0800, Dave Young wrote:
> On 05/28/14 at 08:40am, Vivek Goyal wrote:
> > On Wed, May 28, 2014 at 10:13:59AM +0800, Dave Young wrote:
> > > On 05/27/14 at 09:34am, Vivek Goyal wrote:
> > > > On Mon, May 26, 2014 at 04:39:35PM +0800, Dave Young wrote:
> > > > > 
> > > > > For efi=old_map and any old_map quirks like SGI UV in current
> > > > > tree kexec/kdump will fail because it depends on the new 1:1 mapping.
> > > > > 
> > > > > Thus export the mapping method to sysfs so kexec tools can switch
> > > > > to original way to boot.
> > > > > 
> > > > > Since we have efi.flags for all efi facilities so let's just export the
> > > > > efi.flags itself, it maybe useful for other arches and use cases.
> > > > > 
> > > > 
> > > > Does it require any documentation in Documentation/ABI/..
> > > 
> > > Yes, it's necessary. Will do in next version.
> > > 
> > > I'm still discussing with Matt, exporting efi.flags seems not a good way
> > > because they are more internal interfaces. 
> > > 
> > > Probably I should export only a file 'old_map' instead.
> > 
> > How does /sys/firmware/efi/runtime-map/* look like with old mapping? Can't
> > we look at it and figure out if it is 1:1 or not.
> 
> There's phys_addr and virt_addr, (virt_addr - phys_addr) will always be
> -64G for 1:1 map, ioremapped addresses space is different.

I am curious that what's the meaning of 1:1 mapping here? So far I thought
that means virt and physical addresses are same but that does not seem
to be the case. So what does it mean?

Thanks
Vivek
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