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Message-Id: <20221004081023.32402-2-jgross@suse.com>
Date: Tue, 4 Oct 2022 10:10:08 +0200
From: Juergen Gross <jgross@...e.com>
To: linux-kernel@...r.kernel.org, x86@...nel.org
Cc: Juergen Gross <jgross@...e.com>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
Dave Hansen <dave.hansen@...ux.intel.com>,
"H. Peter Anvin" <hpa@...or.com>
Subject: [PATCH v4 01/16] x86/mtrr: add comment for set_mtrr_state() serialization
Add a comment how set_mtrr_state() is needing serialization.
Suggested-by: Borislav Petkov <bp@...en8.de>
Signed-off-by: Juergen Gross <jgross@...e.com>
---
V3:
- new patch instead of old patch 1
---
arch/x86/kernel/cpu/mtrr/generic.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kernel/cpu/mtrr/generic.c b/arch/x86/kernel/cpu/mtrr/generic.c
index 558108296f3c..cd64eab02393 100644
--- a/arch/x86/kernel/cpu/mtrr/generic.c
+++ b/arch/x86/kernel/cpu/mtrr/generic.c
@@ -684,7 +684,10 @@ static u32 deftype_lo, deftype_hi;
/**
* set_mtrr_state - Set the MTRR state for this CPU.
*
- * NOTE: The CPU must already be in a safe state for MTRR changes.
+ * NOTE: The CPU must already be in a safe state for MTRR changes, including
+ * measures that only a single CPU can be active in set_mtrr_state() in
+ * order to not be subject to races for usage of deftype_lo (this is
+ * accomplished by taking set_atomicity_lock).
* RETURNS: 0 if no changes made, else a mask indicating what was changed.
*/
static unsigned long set_mtrr_state(void)
--
2.35.3
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