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Message-ID: <167336831878.4906.1036202649956155536.tip-bot2@tip-bot2>
Date: Tue, 10 Jan 2023 16:31:58 -0000
From: "tip-bot2 for Juergen Gross" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: "Michael Kelley (LINUX)" <mikelley@...rosoft.com>,
Juergen Gross <jgross@...e.com>,
"Borislav Petkov (AMD)" <bp@...en8.de>, <stable@...nel.org>,
x86@...nel.org, linux-kernel@...r.kernel.org
Subject: [tip: x86/urgent] x86/pat: Fix pat_x_mtrr_type() for MTRR disabled case
The following commit has been merged into the x86/urgent branch of tip:
Commit-ID: 90b926e68f500844dff16b5bcea178dc55cf580a
Gitweb: https://git.kernel.org/tip/90b926e68f500844dff16b5bcea178dc55cf580a
Author: Juergen Gross <jgross@...e.com>
AuthorDate: Tue, 10 Jan 2023 07:54:27 +01:00
Committer: Borislav Petkov (AMD) <bp@...en8.de>
CommitterDate: Tue, 10 Jan 2023 17:21:53 +01:00
x86/pat: Fix pat_x_mtrr_type() for MTRR disabled case
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@...rosoft.com>
Signed-off-by: Juergen Gross <jgross@...e.com>
Signed-off-by: Borislav Petkov (AMD) <bp@...en8.de>
Reviewed-by: Michael Kelley <mikelley@...rosoft.com>
Tested-by: Michael Kelley <mikelley@...rosoft.com>
Cc: <stable@...nel.org>
Link: https://lore.kernel.org/r/20230110065427.20767-1-jgross@suse.com
---
arch/x86/mm/pat/memtype.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/arch/x86/mm/pat/memtype.c b/arch/x86/mm/pat/memtype.c
index 46de9cf..fb4b1b5 100644
--- a/arch/x86/mm/pat/memtype.c
+++ b/arch/x86/mm/pat/memtype.c
@@ -387,7 +387,8 @@ 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;
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