linux-kernel - Re: [PATCH 02/11] PCI: Try to allocate mem64 above 4G at first

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Date:	Fri, 25 May 2012 14:58:52 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Bjorn Helgaas <bhelgaas@...gle.com>
CC:	Yinghai Lu <yinghai@...nel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Steven Newbury <steve@...wbury.org.uk>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 02/11] PCI: Try to allocate mem64 above 4G at first

On 05/25/2012 02:55 PM, Bjorn Helgaas wrote:
> 
> I think we actually have a separate bug here.  On 64-bit non-x86
> architectures, PCIBIOS_MAX_MEM_32 is a 64-bit -1, so the following
> attempt to avoid putting a 32-bit BAR above 4G only works on x86,
> where PCIBIOS_MAX_MEM_32 is 0xffffffff.
> 
>         /* don't allocate too high if the pref mem doesn't support 64bit*/
>         if (!(res->flags & IORESOURCE_MEM_64))
>                 max = PCIBIOS_MAX_MEM_32;
> 
> I think we should fix this with a separate patch that removes
> PCIBIOS_MAX_MEM_32 altogether, replacing this use with an explicit
> 0xffffffff (or some other "max 32-bit value" symbol).  I don't think
> there's anything arch-specific about this.
> 
> So I'd like to see two patches here:
>   1) Avoid allocating 64-bit regions for 32-bit BARs
>   2) Try to allocate regions above 4GB for 64-bit BARs
> 

Do we also need to track the maximum address available to the CPU?

	-hpa

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