> Execute "int $2" to handle NMI in NMI caused VM exits when FRED is enabled. > > Like IRET for IDT, ERETS/ERETU are required to end the NMI handler for FRED > to unblock NMI ASAP (w/ bit 28 of CS set). And there are 2 approaches to > invoke the FRED NMI handler: > 1) execute "int $2", let the h/w do the job. > 2) create a FRED NMI stack frame on the current kernel stack with ASM, > and then jump to fred_entrypoint_kernel in arch/x86/entry/entry_64_fred.S. > > 1) is preferred as we want less ASM. > > Tested-by: Shan Kang <shan.kang@xxxxxxxxx> > Signed-off-by: Xin Li <xin3.li@xxxxxxxxx> > --- > > Changes since v4: > *) Do NOT use the term "injection", which in the KVM context means to > reinject an event into the guest (Sean Christopherson). > *) Add the explanation of why to execute "int $2" to invoke the NMI handler > in NMI caused VM exits (Sean Christopherson). Sean, Do you have any further issue with the last 2 VMX patches? If not, would you ack them? Thanks! Xin > --- > arch/x86/kvm/vmx/vmx.c | 11 ++++++++++- > 1 file changed, 10 insertions(+), 1 deletion(-) > > diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c > index 3ebeaab34b2e..4f12ead2266b 100644 > --- a/arch/x86/kvm/vmx/vmx.c > +++ b/arch/x86/kvm/vmx/vmx.c > @@ -7229,7 +7229,16 @@ static noinstr void vmx_vcpu_enter_exit(struct > kvm_vcpu *vcpu, > if ((u16)vmx->exit_reason.basic == EXIT_REASON_EXCEPTION_NMI && > is_nmi(vmx_get_intr_info(vcpu))) { > kvm_before_interrupt(vcpu, KVM_HANDLING_NMI); > - vmx_do_nmi_irqoff(); > + /* > + * Like IRET for IDT, ERETS/ERETU are required to end the NMI > + * handler for FRED to unblock NMI ASAP (w/ bit 28 of CS set). > + * > + * Invoke the FRED NMI handler through executing "int $2". > + */ > + if (cpu_feature_enabled(X86_FEATURE_FRED)) > + asm volatile("int $2"); > + else > + vmx_do_nmi_irqoff(); > kvm_after_interrupt(vcpu); > } > > -- > 2.34.1