linux-kernel - Re: PCI resource problems caused by improper address rounding

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Message-Id: <20071222011218.0a5cfa42.akpm@linux-foundation.org>
Date:	Sat, 22 Dec 2007 01:12:18 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Ivan Kokshaysky <ink@...assic.park.msu.ru>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Richard Henderson <rth@...ddle.net>,
	Chuck Ebbert <cebbert@...hat.com>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Daniel Ritz <daniel.ritz@....ch>, Greg KH <greg@...ah.com>
Subject: Re: PCI resource problems caused by improper address rounding

On Thu, 20 Dec 2007 11:46:16 +0300 Ivan Kokshaysky <ink@...assic.park.msu.ru> wrote:

> PCI: do respect full 64-bit address for bridge prefetch window
> 
> Prevent the prefetch window from being programmed with a bogus address
> when its respective resource gets allocated above the 4G mark.
> 
> Note that we cannot yet guarantee correct resource allocations
> above 4G, though it might work in some simple cases.
> 

So.. did we agree that this patch is good to go?

> --- a/drivers/pci/setup-bus.c
> +++ b/drivers/pci/setup-bus.c
> @@ -208,8 +208,11 @@ pci_setup_bridge(struct pci_bus *bus)
>  	}
>  	pci_write_config_dword(bridge, PCI_PREF_MEMORY_BASE, l);
>  
> -	/* Clear out the upper 32 bits of PREF base. */
> -	pci_write_config_dword(bridge, PCI_PREF_BASE_UPPER32, 0);
> +	/* Set up the upper 32 bits of PREF base/limit. */
> +	l = region.start >> 16 >> 16;

We have the little upper_32_bits() helper for this.

> +	pci_write_config_dword(bridge, PCI_PREF_BASE_UPPER32, l);
> +	l = region.end >> 16 >> 16;
> +	pci_write_config_dword(bridge, PCI_PREF_LIMIT_UPPER32, l);
>  
>  	pci_write_config_word(bridge, PCI_BRIDGE_CONTROL, bus->bridge_ctl);
>  }

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