From 491c1ad1ac8d891aa440eb0216d023af6c038346 Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Fri, 27 Sep 2019 14:45:19 -0700 Subject: [PATCH] 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 [Replace "else" with early "return" in the unrestricted guest branch. - Paolo] Signed-off-by: Paolo Bonzini --- arch/x86/kvm/vmx/vmx.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index cc83abc93f6d..9eb35e6cbc3f 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -1431,9 +1431,16 @@ 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; - __set_bit(VCPU_EXREG_RFLAGS, (ulong *)&vcpu->arch.regs_avail); + 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;