RE: Out of mtrrs

From: Pallipadi, Venkatesh
Date: Fri Aug 29 2008 - 18:56:54 EST




>-----Original Message-----
>From: linux-kernel-owner@xxxxxxxxxxxxxxx
>[mailto:linux-kernel-owner@xxxxxxxxxxxxxxx] On Behalf Of "J.A.
>Magallón"
>Sent: Friday, August 29, 2008 8:33 AM
>To: Linux-Kernel
>Subject: Out of mtrrs
>
>Hi all...
>
>I'm using the xorg intel driver, and drm/X report it has no free mtrrs
>in kernel to set up:
>
>one:~# cat /proc/mtrr
>reg00: base=0xfffe0000 (4095MB), size= 128KB: write-protect, count=1
>reg01: base=0xfffc0000 (4095MB), size= 128KB: uncachable, count=1
>reg02: base=0x00000000 ( 0MB), size= 256MB: write-back, count=1
>reg03: base=0x10000000 ( 256MB), size= 256MB: write-back, count=1
>reg04: base=0x1f800000 ( 504MB), size= 8MB: uncachable, count=1
>reg05: base=0x1f600000 ( 502MB), size= 2MB: uncachable, count=1
>reg06: base=0x1f500000 ( 501MB), size= 1MB: uncachable, count=1
>reg07: base=0x00000000 ( 0MB), size= 128KB: uncachable, count=1
>
>dmesg:
>
>[drm] Initialized i915 1.6.0 20060119 on minor 0
>mtrr: no more MTRRs available
>
>one:/var/log# grep Linear x.log
>(--) intel(0): Linear framebuffer at 0x20000000
>
>I think X tries to get a mtrr at 0x20000000, but kernel has no free one
>to offer.
>
>Does this have any solution ?
>

One of the main motivations to add PAT support was this kind of errors.
With PAT aware X, this will no longer be a problem as X will map this
using PAT APIs.

Thanks,
Venki
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