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[v3,01/10] x86/mtrr: add comment for set_mtrr_state() serialization

Message ID 20220908084914.21703-2-jgross@suse.com (mailing list archive)
State New, archived
Headers show
Series x86: make pat and mtrr independent from each other | expand

Commit Message

Jürgen Groß Sept. 8, 2022, 8:49 a.m. UTC 
Add a comment how set_mtrr_state() is needing serialization.

Suggested-by: Borislav Petkov <bp@alien8.de>
Signed-off-by: Juergen Gross <jgross@suse.com>
---
V3:
- new patch instead of old patch 1
---
 arch/x86/kernel/cpu/mtrr/generic.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)
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Patch

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)