Re: PCI resource problems caused by improper address rounding

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Linus Torvalds wrote:

On Tue, 18 Dec 2007, Richard Henderson wrote:
I've added dmesg, /proc/iomem, and lspci -v output to that bug.

Basically, we have

	c0000000-cfffffff : free
	ddf00000-dfefffff : PCI Bus #04
	e0000000-efffffff : pnp 00:0b
	f0000000-fedfffff : less than 256MB

Gaah. That really is very unlucky. That 256M only goes at one point in the low 4GB, but the thing is, it fits perfectly well above it, and dammit, that resource is explicitly a 64-bit resource or a really good reason.
However, I wonder about that

	e0000000-efffffff : pnp 00:0b

thing. I actually suspect that that whole allocation is literally *meant* for that 256MB graphics aperture, but the kernel explicitly avoids it because it's listed in the PnP tables.

That is probably the MMCONFIG aperture, in that case any attempt to map the graphics BAR there will have disastrous results. (This BIOS has an MCFG table, though it looks like this Fedora kernel has MMCONFIG disabled, so we can't tell what it actually contains.)

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Robert Hancock      Saskatoon, SK, Canada
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Home Page: http://www.roberthancock.com/

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