linux-kernel - Re: GPT detection regression in efi.c from commit 27a7c64

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Date:	Fri, 13 Sep 2013 10:37:38 -0700
From:	Davidlohr Bueso <davidlohr@...com>
To:	Matt Porter <matt.porter@...aro.org>
Cc:	Karel Zak <kzak@...hat.com>, Matt Fleming <matt.fleming@...el.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	torvalds@...ux-foundation.org
Subject: Re: GPT detection regression in efi.c from commit 27a7c64

On Fri, 2013-09-13 at 13:01 -0400, Matt Porter wrote:
> On 09/13/2013 12:28 PM, Davidlohr Bueso wrote:
[...]
> 
> >> I get that this is not compliant with UEFI. I bring this up because
> >> before this commit the is_pmbr_valid() check was less pedantic. In 3.11
> >> a PMBR formatted this way did not fail the check. For my particular
> >> case, I simply dded out LBA 1 and whacked the SizeInLBA field to comply
> >> with the spec and this patch and I'm back in business. We're updating
> >> the tools that we inherited to prepopulate our boards with a GPT to be
> >> compliant. However, I wondered if this would be a problem for all the
> >> people with Windows-generated GPTs as noted in [1].
> >
> > I guess this comes down to choosing whether or not we want Linux to be
> > more UEFI compliant or not. Should we care if Microsoft decides to go do
> > things out of the official spec? I don't know the policy here. The fact
> > is that *they* should update their partitioning tools and create valid
> > pMBRs. Any way, I'm ok with reverting this commit if deemed necessary.
> 
> I can't say first-hand that Windows 7/8 does what is claimed in this 
> description as I simply don't have access to any Windows machines here. 
> If it's true, I would have to agree with Linus that meeting reality if 
> more important than meeting the spec.

Yep, me too.

> 
> Hopefully somebody can confirm that Windows does indeed produce these 
> special PMBRs that need to be handled as an exception to the spec.

I've got a partition with Windows 7 and I can take a look during the
weekend. Do you know exactly what tool was used for creating the
partition?

Thanks,
Davidlohr

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