[PATCH] 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 MTRR or fixed-range
MTRR support, accessing MTRR MSRs triggers unchecked MSR access error.
Make sure fixed-range MTRR is supported before access to prevent such
error.

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>
---
 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..ca37b374d1b0 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 (boot_cpu_has(X86_FEATURE_MTRR) && mtrr_state.have_fixed)
 		get_fixed_ranges(mtrr_state.fixed_ranges);
 }
 
-- 
2.43.0