x86: unmask CPUID levels on Intel CPUs, fix (99fb4d34) · Commits · 戴 / test

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 <mingo@elte.hu>

arch/x86/kernel/cpu/intel.c

+11 −8

Original line number	Diff line number	Diff line
		@@ -29,15 +29,18 @@

		static void __cpuinit early_init_intel(struct cpuinfo_x86 *c)
		{
		/* Unmask CPUID levels if masked: */
		if (c->x86 == 6 && c->x86_model >= 15) {
		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)) {
		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) \|\|
		(c->x86 == 0x6 && c->x86_model >= 0x0e))

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