From 5b0e508415a83989fe704b4718a1a214bc333ca7 Mon Sep 17 00:00:00 2001 From: Jan Beulich Date: Mon, 10 Mar 2008 13:11:17 +0000 Subject: x86: prevent unconditional writes to DebugCtl MSR Otherwise, enabling (or better, subsequent disabling) of single stepping would cause a kernel oops on CPUs not having this MSR. The patch could have been added a conditional to the MSR write in user_disable_single_step(), but centralizing the updates seems safer and (looking forward) better manageable. Signed-off-by: Jan Beulich Cc: Markus Metzger Signed-off-by: Ingo Molnar --- include/asm-x86/processor.h | 9 +++++++++ 1 file changed, 9 insertions(+) (limited to 'include/asm-x86') diff --git a/include/asm-x86/processor.h b/include/asm-x86/processor.h index cc0268395ea..40227c9bf51 100644 --- a/include/asm-x86/processor.h +++ b/include/asm-x86/processor.h @@ -741,6 +741,15 @@ extern void switch_to_new_gdt(void); extern void cpu_init(void); extern void init_gdt(int cpu); +static inline void update_debugctlmsr(unsigned long debugctlmsr) +{ +#ifndef CONFIG_X86_DEBUGCTLMSR + if (boot_cpu_data.x86 < 6) + return; +#endif + wrmsrl(MSR_IA32_DEBUGCTLMSR, debugctlmsr); +} + /* * from system description table in BIOS. Mostly for MCA use, but * others may find it useful: -- cgit