From 99fb4d349db7e7dacb2099c5cc320a9e2d31c1ef Mon Sep 17 00:00:00 2001 From: Ingo Molnar Date: Mon, 26 Jan 2009 04:30:41 +0100 Subject: [PATCH] x86: unmask CPUID levels on Intel CPUs, fix Impact: fix boot hang on pre-model-15 Intel CPUs rdmsrl_safe() does not work in very early bootup code yet, because we dont have the pagefault handler installed yet so exception section does not get parsed. rdmsr_safe() will just crash and hang the bootup. So limit the MSR_IA32_MISC_ENABLE MSR read to those CPU types that support it. Signed-off-by: Ingo Molnar --- arch/x86/kernel/cpu/intel.c | 19 +++++++++++-------- 1 file changed, 11 insertions(+), 8 deletions(-) diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c index 43c1dcf0bec..549f2ada55f 100644 --- a/arch/x86/kernel/cpu/intel.c +++ b/arch/x86/kernel/cpu/intel.c @@ -29,14 +29,17 @@ static void __cpuinit early_init_intel(struct cpuinfo_x86 *c) { - u64 misc_enable; - - /* Unmask CPUID levels if masked */ - if (!rdmsrl_safe(MSR_IA32_MISC_ENABLE, &misc_enable) && - (misc_enable & MSR_IA32_MISC_ENABLE_LIMIT_CPUID)) { - misc_enable &= ~MSR_IA32_MISC_ENABLE_LIMIT_CPUID; - wrmsrl(MSR_IA32_MISC_ENABLE, misc_enable); - c->cpuid_level = cpuid_eax(0); + /* Unmask CPUID levels if masked: */ + if (c->x86 == 6 && c->x86_model >= 15) { + u64 misc_enable; + + rdmsrl(MSR_IA32_MISC_ENABLE, misc_enable); + + if (misc_enable & MSR_IA32_MISC_ENABLE_LIMIT_CPUID) { + misc_enable &= ~MSR_IA32_MISC_ENABLE_LIMIT_CPUID; + wrmsrl(MSR_IA32_MISC_ENABLE, misc_enable); + c->cpuid_level = cpuid_eax(0); + } } if ((c->x86 == 0xf && c->x86_model >= 0x03) || -- 2.20.1