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KVM: x86: Remove redundant vm_entry_controls_clearbit() call

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When emulating exit from long mode, EFER_LMA is cleared with
vmx_set_efer().  This will already unset the VM_ENTRY_IA32E_MODE control
bit as requested by SDM, so there is no need to unset VM_ENTRY_IA32E_MODE
again in exit_lmode() explicitly.  In case EFER isn't supported by
hardware, long mode isn't supported, so exit_lmode() cannot be reached.

Note that, thanks to the shadow controls mechanism, this change doesn't
eliminate vmread or vmwrite.

Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
Message-Id: <20220311102643.807507-3-zhenzhong.duan@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Zhenzhong Duan 2022-03-11 18:26:43 +08:00 committed by Paolo Bonzini
parent b76edfe91a
commit 4335edbbc1
1 changed files with 0 additions and 1 deletions
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arch/x86/kvm/vmx/vmx.c
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@ -2902,7 +2902,6 @@ static void enter_lmode(struct kvm_vcpu *vcpu)
static void exit_lmode(struct kvm_vcpu *vcpu)
{
vm_entry_controls_clearbit(to_vmx(vcpu), VM_ENTRY_IA32E_MODE);
vmx_set_efer(vcpu, vcpu->arch.efer & ~EFER_LMA);
}