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Re: [PATCH 2/2] x86/pat: add functions to query specific cache mode availability



On 5/19/22 10:15 PM, Chuck Zmudzinski wrote:
On 5/3/22 9:22 AM, Juergen Gross wrote:
Some drivers are using pat_enabled() in order to test availability of
special caching modes (WC and UC-). This will lead to false negatives
in case the system was booted e.g. with the "nopat" variant and the
BIOS did setup the PAT MSR supporting the queried mode, or if the
system is running as a Xen PV guest.
Hello,

I am also getting a false positive

Sorry, I meant false negative here, not false
positive.

Chuck

in a Xen Dom0 from
pat_enabled() where bdd8b6c98239 patched the file

drivers/gpu/drm/i915/gem/i915_gem_pages.c

I think this patch also needs to touch that file to
fix the issue I am seeing.
...




 


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