x86/mtrr: Revert 90b926e68f50 ("x86/pat: Fix pat_x_mtrr_type() for MTRR disabled...

Commit

  90b926e68f50 ("x86/pat: Fix pat_x_mtrr_type() for MTRR disabled case")

broke the use case of running Xen dom0 kernels on machines with an
external disk enclosure attached via USB, see Link tag.

What this commit was originally fixing - SEV-SNP guests on Hyper-V - is
a more specialized situation which has other issues at the moment anyway
so reverting this now and addressing the issue properly later is the
prudent thing to do.

So revert it in time for the 6.2 proper release.

  [ bp: Rewrite commit message. ]

Reported-by: Christian Kujau <lists@nerdbynature.de>
Tested-by: Christian Kujau <lists@nerdbynature.de>
Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/4fe9541e-4d4c-2b2a-f8c8-2d34a7284930@nerdbynature.de

diff --git a/arch/x86/mm/pat/memtype.c b/arch/x86/mm/pat/memtype.c
index fb4b1b5e0deab2fcbd1f1a2442431fe63adbbc24..46de9cf5c91d2be26a72afdd4de86b87c2b2c3c2 100644 (file)
--- a/arch/x86/mm/pat/memtype.c
+++ b/arch/x86/mm/pat/memtype.c
@@ -387,8 +387,7 @@ static unsigned long pat_x_mtrr_type(u64 start, u64 end,
                u8 mtrr_type, uniform;
 
                mtrr_type = mtrr_type_lookup(start, end, &uniform);
-               if (mtrr_type != MTRR_TYPE_WRBACK &&
-                   mtrr_type != MTRR_TYPE_INVALID)
+               if (mtrr_type != MTRR_TYPE_WRBACK)
                        return _PAGE_CACHE_MODE_UC_MINUS;
 
                return _PAGE_CACHE_MODE_WB;