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

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Date:	Fri, 24 May 2013 13:09:11 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	Matt Fleming <matt@...sole-pimps.org>
Cc:	Russ Anderson <rja@....com>,
	Matthew Garrett <matthew.garrett@...ula.com>,
	matt.fleming@...el.com, linux-efi@...r.kernel.org, x86@...nel.org,
	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...ux.intel.com>
Subject: Re: [regression, bisected] x86: efi: Pass boot services variable
 info to runtime code

On Fri, May 24, 2013 at 08:43:31AM +0100, Matt Fleming wrote:
> What appears to be happening is that your the EFI runtime services
> code is calling into the EFI boot services code, which is definitely
> a bug in your firmware because we're at runtime, but we've seen
> other machines that do similar things so we usually handle it just
> fine. However, what makes your case different, and the reason you
> see the above splat, is that it's using the physical address of
> the EFI boot services region, not the virtual one we setup with
> SetVirtualAddressMap(). Which is a second firmware bug.

I'm speechless. Let's have someone else do the ranting this time:

http://www.happyassassin.net/2013/05/03/a-day-in-the-life-of-a-firmware-engineer/

> Again, we have seen other machines that access
> physical addresses after SetVirtualAddressMap(), but until now we
> haven't had any non-optional code that triggered them.
> 
> The only reason I can see that the offending commit would introduce this
> problem is because it calls QueryVariableInfo() at boot time. I notice
> that your machine is an SGI UV one, is there any chance you could get a
> firmware fix for this? If possible, it would be also good to confirm
> that it's this chunk of code in setup_efi_vars(),
> 
> 	status = efi_call_phys4(sys_table->runtime->query_variable_info,
> 				EFI_VARIABLE_NON_VOLATILE |
> 				EFI_VARIABLE_BOOTSERVICE_ACCESS |
> 				EFI_VARIABLE_RUNTIME_ACCESS, &store_size,
> 				&remaining_size, &var_size);
> 
> that later makes GetNextVariable() jump to the physical address of the
> EFI Boot Services region. Because if not, we need to do some more
> digging.
> 
> Borislav, how are your 1:1 mapping patches coming along? In theory, once
> those are merged we can gracefully workaround these kinds of issues.

What do you mean, map boot time functions 1:1 too?

In any case, I think I have an idea about the bug I was discussing with
hpa recently but I need to do more experimenting. I have the next week
off, though, so don't hold your breath just yet :).
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