linux-kernel - Re: [PATCH] x86, pci: Add quirk for unsizeable Broadwell EP bar

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Message-ID: <20160205015734.GA29929@localhost>
Date:	Thu, 4 Feb 2016 19:57:34 -0600
From:	Bjorn Helgaas <helgaas@...nel.org>
To:	Andi Kleen <ak@...ux.intel.com>
Cc:	Andi Kleen <andi@...stfloor.org>, bhelgaas@...gle.com,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org,
	x86@...nel.org
Subject: Re: [PATCH] x86, pci: Add quirk for unsizeable Broadwell EP bar

On Thu, Feb 04, 2016 at 10:54:42AM -0800, Andi Kleen wrote:
> > It sounds like these devices have some device-specific register where
> > BAR 0 is supposed to be?  Setting IORESOURCE_PCI_FIXED doesn't seem
> > like the right solution to me.  Even if we set that, the core still
> 
> There is no actually functional register on these locations that has any side
> effects.
> 
> > believes this resource corresponds to some address space consumed by
> > the device.  I think we will still try to size the BAR and decode its
> > type.  I think it will still show up via lspci.  That's all
> > meaningless.
> 
> But would actually anything use it?

You mean, would anything actually use the lspci output?  I don't know,
but why would we want it to print garbage?

And the kernel certainly uses the struct resource.  Setting
IORESOURCE_PCI_FIXED is not a way of saying "please ignore this
resource."

Bjorn