diff options
| -rw-r--r-- | src/cpu/intel/model_206ax/model_206ax_init.c | 19 |
1 files changed, 16 insertions, 3 deletions
diff --git a/src/cpu/intel/model_206ax/model_206ax_init.c b/src/cpu/intel/model_206ax/model_206ax_init.c index 64c32a0bc9..71879e2b1f 100644 --- a/src/cpu/intel/model_206ax/model_206ax_init.c +++ b/src/cpu/intel/model_206ax/model_206ax_init.c @@ -144,10 +144,23 @@ static void enable_vmx(void) printk(BIOS_DEBUG, "%s VMX\n", enable ? "Enabling" : "Disabling"); + /* Even though the Intel manual says you must set the lock bit in addition + * to the VMX bit in order for VMX to work, it is incorrect. Thus we leave + * it unlocked for the OS to manage things itself. This is good for a few + * reasons: + * - No need to reflash the bios just to toggle the lock bit. + * - The VMX bits really really should match each other across cores, so + * hard locking it on one while another has the opposite setting can + * easily lead to crashes as code using VMX migrates between them. + * - Vendors that want to "upsell" from a bios that disables+locks to + * one that doesn't is sleazy. + * By leaving this to the OS (e.g. Linux), people can do exactly what they + * want on the fly, and do it correctly (e.g. across multiple cores). + */ if (enable) { - msr.lo |= (1 << 2); - if (regs.ecx & CPUID_SMX) - msr.lo |= (1 << 1); + msr.lo |= (1 << 2); + if (regs.ecx & CPUID_SMX) + msr.lo |= (1 << 1); } wrmsr(IA32_FEATURE_CONTROL, msr); |