Re: [PATCH v6 00/16] x86/mtrr: fix handling with PAT but without MTRR

Borislav Petkov
2023-05-09T20:14:46Z

On Tue, May 02, 2023 at 02:09:15PM +0200, Juergen Gross wrote:
> This series tries to fix the rather special case of PAT being available
> without having MTRRs (either due to CONFIG_MTRR being not set, or
> because the feature has been disabled e.g. by a hypervisor).

More weird stuff. With the series:

[root@vh: ~> cat /proc/mtrr
cat: /proc/mtrr: Input/output error

before:

[root@vh: ~> cat /proc/mtrr
reg00: base=0x000000000 ( 0MB), size= 2048MB, count=1: write-back
reg01: base=0x080000000 ( 2048MB), size= 1024MB, count=1: write-back
reg02: base=0x0c0000000 ( 3072MB), size= 256MB, count=1: write-back
reg03: base=0x0ff000000 ( 4080MB), size= 16MB, count=1: write-protect

I think it wrongly determines that MTRRs are disabled by BIOS:

MTRRs disabled by BIOS
x86/PAT: Configuration [0-7]: WB WC UC- UC WB WP UC- WT

which is obviously wrong.

But more debugging later.

--
Regards/Gruss,
Boris.