diff options
| author | Juergen Gross <jgross@suse.com> | 2023-01-10 09:54:27 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2023-01-18 13:58:22 +0300 |
| commit | c1c59538337ab6d45700cb4a1c9725e67f59bc6e (patch) | |
| tree | 9c1cb100373d1694843af27746cef9383e6fa9a0 /arch | |
| parent | 1dc8c5574cc2491016691b86a70fcfa4d05279ce (diff) | |
| download | linux-c1c59538337ab6d45700cb4a1c9725e67f59bc6e.tar.xz | |
x86/pat: Fix pat_x_mtrr_type() for MTRR disabled case
commit 90b926e68f500844dff16b5bcea178dc55cf580a upstream.
Since
72cbc8f04fe2 ("x86/PAT: Have pat_enabled() properly reflect state when running on Xen")
PAT can be enabled without MTRR.
This has resulted in problems e.g. for a SEV-SNP guest running under Hyper-V,
when trying to establish a new mapping via memremap() with WB caching mode, as
pat_x_mtrr_type() will call mtrr_type_lookup(), which in turn is returning
MTRR_TYPE_INVALID due to MTRR being disabled in this configuration.
The result is a mapping with UC- caching, leading to severe performance
degradation.
Fix that by handling MTRR_TYPE_INVALID the same way as MTRR_TYPE_WRBACK
in pat_x_mtrr_type() because MTRR_TYPE_INVALID means MTRRs are disabled.
[ bp: Massage commit message. ]
Fixes: 72cbc8f04fe2 ("x86/PAT: Have pat_enabled() properly reflect state when running on Xen")
Reported-by: Michael Kelley (LINUX) <mikelley@microsoft.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Tested-by: Michael Kelley <mikelley@microsoft.com>
Cc: <stable@kernel.org>
Link: https://lore.kernel.org/r/20230110065427.20767-1-jgross@suse.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/x86/mm/pat/memtype.c | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/arch/x86/mm/pat/memtype.c b/arch/x86/mm/pat/memtype.c index 66a209f7eb86..2642bc4c8ec0 100644 --- a/arch/x86/mm/pat/memtype.c +++ b/arch/x86/mm/pat/memtype.c @@ -434,7 +434,8 @@ 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) + if (mtrr_type != MTRR_TYPE_WRBACK && + mtrr_type != MTRR_TYPE_INVALID) return _PAGE_CACHE_MODE_UC_MINUS; return _PAGE_CACHE_MODE_WB; |