Sean Christopherson <sean.j.christopherson@xxxxxxxxx> writes:
> 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@xxxxxxxxx>
> ---
> arch/x86/kvm/vmx/vmx.c | 28 ++++++++++++++++++----------
> 1 file changed, 18 insertions(+), 10 deletions(-)
>
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index 83fe8b02b732..814d3e6d0264 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -1426,18 +1426,26 @@ 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);
> - vmx->rflags = rflags;
> - if (vmx->rmode.vm86_active) {
> - vmx->rmode.save_rflags = rflags;
> - rflags |= X86_EFLAGS_IOPL | X86_EFLAGS_VM;
> + if (enable_unrestricted_guest) {
> + __set_bit(VCPU_EXREG_RFLAGS, (ulong *)&vcpu->arch.regs_avail);
> +
> + vmx->rflags = rflags;
> + vmcs_writel(GUEST_RFLAGS, rflags);
> + } else {
> + 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;
> + }
> + vmcs_writel(GUEST_RFLAGS, rflags);
> +
> + if ((old_rflags ^ vmx->rflags) & X86_EFLAGS_VM)
> + vmx->emulation_required = emulation_required(vcpu);
> }
> - vmcs_writel(GUEST_RFLAGS, rflags);
We're doing vmcs_writel() in both branches so it could've stayed here, right?
> -
> - if ((old_rflags ^ vmx->rflags) & X86_EFLAGS_VM)
> - vmx->emulation_required = emulation_required(vcpu);
> }
>
> u32 vmx_get_interrupt_shadow(struct kvm_vcpu *vcpu)
Reviewed-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
--
Vitaly
