From: Juergen Gross Date: Tue, 4 Oct 2022 08:10:08 +0000 (+0200) Subject: x86/mtrr: Add comment for set_mtrr_state() serialization X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=01c97c7303580682751b5aaae043b639bdcbacb3;p=linux.git x86/mtrr: Add comment for set_mtrr_state() serialization Add a comment about set_mtrr_state() needing serialization. [ bp: Touchups. ] Suggested-by: Borislav Petkov Signed-off-by: Juergen Gross Signed-off-by: Borislav Petkov Link: https://lore.kernel.org/r/20220820092533.29420-2-jgross@suse.com --- diff --git a/arch/x86/kernel/cpu/mtrr/generic.c b/arch/x86/kernel/cpu/mtrr/generic.c index 558108296f3cf..c8f895157e059 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)