Messages in this thread | | | Subject | Re: [RFC PATCH 4/4] KVM: vmx: add support for emulating UMIP | From | Paolo Bonzini <> | Date | Wed, 13 Jul 2016 11:35:10 +0200 |
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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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