linux-kernel - Re: [PATCH 2/3] x86/sysfb_efi: Fix valid BAR address range check

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Message-ID: <20160504102905.GF2839@codeblueprint.co.uk>
Date:	Wed, 4 May 2016 11:29:05 +0100
From:	Matt Fleming <matt@...eblueprint.co.uk>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	"H . Peter Anvin" <hpa@...or.com>,
	Wang YanQing <udknight@...il.com>,
	Ard Biesheuvel <ard.biesheuvel@...aro.org>,
	linux-kernel@...r.kernel.org, linux-efi@...r.kernel.org,
	David Herrmann <dh.herrmann@...il.com>,
	Peter Jones <pjones@...hat.com>, stable@...r.kernel.org,
	Tomi Valkeinen <tomi.valkeinen@...com>
Subject: Re: [PATCH 2/3] x86/sysfb_efi: Fix valid BAR address range check

On Wed, 04 May, at 12:23:40PM, Ingo Molnar wrote:
> 
> * Matt Fleming <matt@...eblueprint.co.uk> wrote:
> 
> > On Wed, 04 May, at 08:35:24AM, Ingo Molnar wrote:
> > > 
> > > * Matt Fleming <matt@...eblueprint.co.uk> wrote:
> > > 
> > > > From: Wang YanQing <udknight@...il.com>
> > > > 
> > > > We can't just break out when meet start is equal to zero,
> > > 
> > > Hm, wot?
> > 
> > The existing code treats address 0x0 as invalid for a PCI BAR range
> > start address, but 0x0 is actually possible and legitimate, so we
> > shouldn't be breaking out of the loop.
> 
> Yeah, so I just don't understand the 'when meet start is equal to zero' part - 
> what does it mean?

I suspect it means "when start is equal to zero" or "when we encounter
the scenario where start is equal to zero".

Wang?