linux-kernel - Re: [regression, bisected] x86: efi: Pass boot services variable info to runtime code

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Message-ID: <20130531101250.GD30394@gmail.com>
Date:	Fri, 31 May 2013 12:12:50 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Jiri Kosina <jkosina@...e.cz>
Cc:	Russ Anderson <rja@....com>, joeyli <jlee@...e.com>,
	Matt Fleming <matt@...sole-pimps.org>,
	Matthew Garrett <matthew.garrett@...ula.com>,
	matt.fleming@...el.com, linux-efi@...r.kernel.org, x86@...nel.org,
	linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...ux.intel.com>,
	Borislav Petkov <bp@...en8.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [regression, bisected] x86: efi: Pass boot services variable
 info to runtime code


* Jiri Kosina <jkosina@...e.cz> wrote:

> On Thu, 30 May 2013, Russ Anderson wrote:
> 
> > > > > > Yes, but this call is clearly happening way before ExitBootServices() -- 
> > > > > > see the surrounding code, see for example this in efi_main():
> > > > > > 
> > > > > > [ ... snip ... ]
> > > > > > 	setup_efi_vars(boot_params);
> > > > > > 
> > > > > > 	setup_efi_pci(boot_params);
> > > > > > 
> > > > > > 	status = efi_call_phys3(sys_table->boottime->allocate_pool,
> > > > > > 				EFI_LOADER_DATA, sizeof(*gdt),
> > > > > > 				(void **)&gdt);
> > > > > > 	if (status != EFI_SUCCESS) {
> > > > > > 		efi_printk("Failed to alloc mem for gdt structure\n");
> > > > > > 		goto fail;
> > > > > > 	}
> > > > > > [ ... snip ... ]
> > > > > 
> > > > > Yes.  Note the failing call is sys_table->runtime while all the
> > > > > other calls are sys_table->boottime and seem to work.  Not sure
> > > > > why the sys_table->runtime call has a problem but it may be
> > > > > a clue.  Could something in the runtime path not be set up???
> > > > 
> > > > That was my original idea early today as well. My understanding of the 
> > > > UEFI spec is admittedly limited, but afaics calling runtime method from 
> > > > boot environment should be a valid thing to do ... ?
> > > 
> > > QueryVariableInfo() is a runtime services, all runtime services should
> > > available bother on boot time and runtime:
> > > 
> > > UEFI spec 2.3.1 P.109:
> > >   Runtime Services
> > >   Functions that are available before and after any call to  
> > >   ExitBootServices(). These functions are described in Section 7.
> > 
> > That's a great idea.  This patch moves the QueryVariableInfo()
> > call from bootime to runtime, in efi_late_init().  The attached
> > patch is consistent with the UEFI spec and avoids the problem.
> 
> Unfortunately that means that you can as well throw the patch away 
> completely.
> 
> The sole point is to run the QueryVariableInfo() from the boot 
> environment, in order to obtain more accurate information. And it's a 
> valid thing to do, according to UEFI specification.

Argh!

The 'UEFI specification', if contradicted by reality, has _NO VALUE_ 
whatsoever. Full stop.

Any specification is only valuable as long as it's followed by everyone: 
but once that is not the case, it does not matter much what the written 
wishes on the paper express.

What matters is that a system that booted fine with v3.8 does not boot 
anymore due to a change we did to the EFI code. And the only valid 
response to that is to make it work. Full stop!

And this is not only about SGI/UV systems: in this thread there were 
multiple systems mentioned that _DO NOT BOOT_ due to this change.

So this change needs to be reverted or fixed.

Thanks,

	Ingo
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