Messages in this thread |  | | | Date | Sun, 1 Feb 2004 05:10:21 +0000 | | From | Matthew Wilcox <> | | Subject | Re: [patch] PCI Express Enhanced Config Patch - 2.6.0-test11 |
| |
On Sat, Jan 31, 2004 at 02:57:29PM -0700, Eric W. Biederman wrote: > Is it really safe to treat the base address as a u32? I know > if I was doing the BIOS and that address was tied to a 32bit BAR I > would be extremely tempted to put those 256M of address space above > 4G. Putting something like that below 4G leads to 1/2 Gig of memory > missing.
This is actually a Linux limitation -- we're pretty bad at dealing with 64-bit BARs on 32-bit architectures. There's two interfaces to get at it -- ioremap() and set_fixmap(). Both of these interfaces take an unsigned long to describe a physical address.
> Point being I don't think it is safe to assume the BIOS always puts > the extended PCI configuration space below 4G.
MCFG isn't described in any released version of the ACPI spec, so I don't know whether it's even possible for it to be a 64-bit address. There's a reserved field that might be used for the upper 32 bits.
-- "Next the statesmen will invent cheap lies, putting the blame upon the nation that is attacked, and every man will be glad of those conscience-soothing falsities, and will diligently study them, and refuse to examine any refutations of them; and thus he will by and by convince himself that the war is just, and will thank God for the better sleep he enjoys after this process of grotesque self-deception." -- Mark Twain - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
|  |