Re: [PATCH v3.1 10/12] x86/mtrr: use new cache_map in mtrr_type_lookup()

[Juergen Gross]

On 26.02.23 18:00, Michael Kelley (LINUX) wrote:
> From: Juergen Gross <jgross@xxxxxxxx> Sent: Thursday, February 23, 2023 10:37 PM
> > Instead of crawling through the MTRR register state, use the new
> > cache_map for looking up the cache type(s) of a memory region.
> >
> > This allows now to set the uniform parameter according to the
> > uniformity of the cache mode of the region, instead of setting it
> > only if the complete region is mapped by a single MTRR. This now
> > includes even the region covered by the fixed MTRR registers.
> >
> > Make sure uniform is always set.
> >
> > Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
> > ---
> > V3:
> > - new patch
> > V3.1:
> > - fix type_merge() (Michael Kelley)
>
> Thanks.  This version fixes the problem I previously reported with a normal
> VM.
>
> However, I'm seeing a different problem in a Confidential VM where
> mtrr_overwrite_state() is used.  In this case, we have no MTRRs, and when
> mtrr_copy_map() is called, the copy is not done, and cache_map is set
> to NULL.  Subsequently when mtrr_type_lookup() is called, the check
> for a NULL cache_map causes MTRR_TYPE_UNCACHABLE to be returned.
> Then we're back to the original problem where pat_x_mtrr_type()
> returns UC- instead of WB.

Sigh. Just removing the test for cache_map being NULL in mtrr_type_lookup()
should do the job.

Will send V4 soon.


Juergen

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