[PATCH v2] x86/mtrr: Check if fixed-range MTRR exists in mtrr_save_fixed_ranges()

[Jiaqing Zhao]

When suspending, save_processor_state() calls mtrr_save_fixed_ranges()
to save fixed-range MTRRs. On platforms without fixed-range MTRRs,
accessing these MSRs will trigger unchecked MSR access error. Make
sure fixed-range MTRRs are supported before access to prevent such
error.

Since mtrr_state.have_fixed is only set when MTRRs are present and
enabled, checking the CPU feature flag in mtrr_save_fixed_ranges()
is unnecessary.

Fixes: 3ebad5905609 ("[PATCH] x86: Save and restore the fixed-range MTRRs of the BSP when suspending")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Jiaqing Zhao <jiaqing.zhao@xxxxxxxxxxxxxxx>
---
v2:
* Removed unnecessary boot_cpu_has(X86_FEATURE_MTRR) check.
* Updated commit message.
Link: https://lore.kernel.org/all/20250509085612.2236222-2-jiaqing.zhao@xxxxxxxxxxxxxxx

 arch/x86/kernel/cpu/mtrr/generic.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/mtrr/generic.c b/arch/x86/kernel/cpu/mtrr/generic.c
index e2c6b471d230..8c18327eb10b 100644
--- a/arch/x86/kernel/cpu/mtrr/generic.c
+++ b/arch/x86/kernel/cpu/mtrr/generic.c
@@ -593,7 +593,7 @@ static void get_fixed_ranges(mtrr_type *frs)
 
 void mtrr_save_fixed_ranges(void *info)
 {
-	if (boot_cpu_has(X86_FEATURE_MTRR))
+	if (mtrr_state.have_fixed)
 		get_fixed_ranges(mtrr_state.fixed_ranges);
 }
 
-- 
2.43.0