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| author | Andi Kleen <ak@linux.intel.com> | 2024-08-08 03:02:44 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2024-08-14 16:34:34 +0300 |
| commit | 388f1c954019f253a8383f7eb733f38d541e10b6 (patch) | |
| tree | baaef6fbcd205cb20230159db2c7455604b5ab2c | |
| parent | 718ea0de5c9d71c588366e2e77e2d088b3ab7405 (diff) | |
| download | linux-388f1c954019f253a8383f7eb733f38d541e10b6.tar.xz | |
x86/mtrr: Check if fixed MTRRs exist before saving them
commit 919f18f961c03d6694aa726c514184f2311a4614 upstream.
MTRRs have an obsolete fixed variant for fine grained caching control
of the 640K-1MB region that uses separate MSRs. This fixed variant has
a separate capability bit in the MTRR capability MSR.
So far all x86 CPUs which support MTRR have this separate bit set, so it
went unnoticed that mtrr_save_state() does not check the capability bit
before accessing the fixed MTRR MSRs.
Though on a CPU that does not support the fixed MTRR capability this
results in a #GP. The #GP itself is harmless because the RDMSR fault is
handled gracefully, but results in a WARN_ON().
Add the missing capability check to prevent this.
Fixes: 2b1f6278d77c ("[PATCH] x86: Save the MTRRs of the BSP before booting an AP")
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/all/20240808000244.946864-1-ak@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | arch/x86/kernel/cpu/mtrr/mtrr.c | 2 |
1 files changed, 1 insertions, 1 deletions
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); |