From 066941bd4eeb159307a5d7d795100d0887c00442 Mon Sep 17 00:00:00 2001 From: "H. Peter Anvin" Date: Wed, 21 Jan 2009 15:04:32 -0800 Subject: [PATCH] x86: unmask CPUID levels on Intel CPUs Impact: Fixes crashes with misconfigured BIOSes on XSAVE hardware Avuton Olrich reported early boot crashes with v2.6.28 and bisected it down to dc1e35c6e95e8923cf1d3510438b63c600fee1e2 ("x86, xsave: enable xsave/xrstor on cpus with xsave support"). If the CPUID limit bit in MSR_IA32_MISC_ENABLE is set, clear it to make all CPUID information available. This is required for some features to work, in particular XSAVE. Reported-and-bisected-by: Avuton Olrich Tested-by: Avuton Olrich Signed-off-by: H. Peter Anvin --- arch/x86/kernel/cpu/intel.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c index 8ea6929e974..43c1dcf0bec 100644 --- a/arch/x86/kernel/cpu/intel.c +++ b/arch/x86/kernel/cpu/intel.c @@ -29,6 +29,16 @@ 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); + } + if ((c->x86 == 0xf && c->x86_model >= 0x03) || (c->x86 == 0x6 && c->x86_model >= 0x0e)) set_cpu_cap(c, X86_FEATURE_CONSTANT_TSC); -- 2.41.1