Commit 491c1ad1 authored Sep 27, 2019 by Sean Christopherson Committed by Paolo Bonzini Oct 22, 2019

KVM: VMX: Optimize vmx_set_rflags() for unrestricted guest



Rework vmx_set_rflags() to avoid the extra code need to handle emulation
of real mode and invalid state when unrestricted guest is disabled.  The
primary reason for doing so is to avoid the call to vmx_get_rflags(),
which will incur a VMREAD when RFLAGS is not already available.  When
running nested VMs, the majority of calls to vmx_set_rflags() will occur
without an associated vmx_get_rflags(), i.e. when stuffing GUEST_RFLAGS
during transitions between vmcs01 and vmcs02.

Note, vmx_get_rflags() guarantees RFLAGS is marked available.

Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
[Replace "else" with early "return" in the unrestricted guest branch. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

parent e7bddc52

arch/x86/kvm/vmx/vmx.c

+9 −2

Original line number	Diff line number	Diff line
		@@ -1431,10 +1431,17 @@ unsigned long vmx_get_rflags(struct kvm_vcpu *vcpu)
		void vmx_set_rflags(struct kvm_vcpu *vcpu, unsigned long rflags)
		{
		struct vcpu_vmx *vmx = to_vmx(vcpu);
		unsigned long old_rflags = vmx_get_rflags(vcpu);
		unsigned long old_rflags;

		if (enable_unrestricted_guest) {
		__set_bit(VCPU_EXREG_RFLAGS, (ulong *)&vcpu->arch.regs_avail);
		vmx->rflags = rflags;
		vmcs_writel(GUEST_RFLAGS, rflags);
		return;
		}

		old_rflags = vmx_get_rflags(vcpu);
		vmx->rflags = rflags;
		if (vmx->rmode.vm86_active) {
		vmx->rmode.save_rflags = rflags;
		rflags \|= X86_EFLAGS_IOPL \| X86_EFLAGS_VM;

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