linux-kernel - [PATCH] x86/mtrr: Check if fixed-range MTRR exists in `mtrr_save_fixed

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Message-ID: <20250509085612.2236222-2-jiaqing.zhao@linux.intel.com>
Date: Fri,  9 May 2025 08:56:12 +0000
From: Jiaqing Zhao <jiaqing.zhao@...ux.intel.com>
To: Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	x86@...nel.org,
	"H. Peter Anvin" <hpa@...or.com>,
	Bernhard Kaindl <bk@...e.de>,
	Andi Kleen <ak@...ux.intel.com>
Cc: Li Fei <fei1.li@...el.com>,
	Jiaqing Zhao <jiaqing.zhao@...ux.intel.com>,
	stable@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] x86/mtrr: Check if fixed-range MTRR exists in `mtrr_save_fixed_ranges`

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@...r.kernel.org
Signed-off-by: Jiaqing Zhao <jiaqing.zhao@...ux.intel.com>
---
 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