On 13/07/2016 11:21, Yang Zhang wrote:
>>
>> + if ((cr4 & X86_CR4_UMIP) && !boot_cpu_has(X86_FEATURE_UMIP)) {
>> + vmcs_set_bits(SECONDARY_VM_EXEC_CONTROL,
>> + SECONDARY_EXEC_DESC);
>> + hw_cr4 &= ~X86_CR4_UMIP;
>> + } else
>> + vmcs_clear_bits(SECONDARY_VM_EXEC_CONTROL,
>> + SECONDARY_EXEC_DESC);
>> +
>
> Since the faults based on privilege level have priority over VM exits.
> So we don't need to enable/disable SECONDARY_EXEC_DESC dynamically.
> Instead, we can set it unconditionally.
I'm setting it dynamically because it slows down LGDT, LLDT, LIDT and LTR.
Paolo
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