linux-kernel - [PATCH v2] x86/mtrr: Check if fixed MTRRs exist before saving them

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Message-ID: <20240110150806.22531-1-ak@linux.intel.com>
Date: Wed, 10 Jan 2024 07:08:06 -0800
From: Andi Kleen <ak@...ux.intel.com>
To: x86@...nel.org
Cc: linux-kernel@...r.kernel.org,
	Andi Kleen <ak@...ux.intel.com>
Subject: [PATCH v2] x86/mtrr: Check if fixed MTRRs exist before saving them

This one place forgot to check the fixed capability. Otherwise there
will a harmless but ugly WARN_ON for the failed WRMSR when the MSR
doesn't exist. Noticed when testing X86S support.

Fixes: 2b1f6278d77c ("[PATCH] x86: Save the MTRRs of the BSP before")
Signed-off-by: Andi Kleen <ak@...ux.intel.com>

---

v2: Add Fixes tag and expand description.
---
 arch/x86/kernel/cpu/mtrr/mtrr.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/mtrr/mtrr.c b/arch/x86/kernel/cpu/mtrr/mtrr.c
index 767bf1c71aad..2a2fc14955cd 100644
--- a/arch/x86/kernel/cpu/mtrr/mtrr.c
+++ b/arch/x86/kernel/cpu/mtrr/mtrr.c
@@ -609,7 +609,7 @@ void mtrr_save_state(void)
 {
 	int first_cpu;
 
-	if (!mtrr_enabled())
+	if (!mtrr_enabled() || !mtrr_state.have_fixed)
 		return;
 
 	first_cpu = cpumask_first(cpu_online_mask);
-- 
2.43.0