Re: [PATCH v19 102/130] KVM: TDX: handle EXCEPTION_NMI and EXTERNAL_INTERRUPT

[Binbin Wu]

On 4/4/2024 2:51 AM, Isaku Yamahata wrote:
> On Mon, Apr 01, 2024 at 04:22:00PM +0800,
> Chao Gao <chao.gao@xxxxxxxxx> wrote:
>
> > On Mon, Feb 26, 2024 at 12:26:44AM -0800, isaku.yamahata@xxxxxxxxx wrote:
> > > From: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
> > >
> > > Because guest TD state is protected, exceptions in guest TDs can't be
> > > intercepted.  TDX VMM doesn't need to handle exceptions.
> > > tdx_handle_exit_irqoff() handles NMI and machine check.  Ignore NMI and
> > tdx_handle_exit_irqoff() doesn't handle NMIs.
> Will it to tdx_handle_exception().

I don't get  why tdx_handle_exception()?

NMI is handled in tdx_vcpu_enter_exit() prior to leaving the safety of 
noinstr, according to patch 098.
https://lore.kernel.org/kvm/88920c598dcb55c15219642f27d0781af6d0c044.1708933498.git.isaku.yamahata@xxxxxxxxx/

@@ -837,6 +857,12 @@ static noinstr void tdx_vcpu_enter_exit(struct 
vcpu_tdx *tdx)
     WARN_ON_ONCE(!kvm_rebooting &&
              (tdx->exit_reason.full & TDX_SW_ERROR) == TDX_SW_ERROR);

+    if ((u16)tdx->exit_reason.basic == EXIT_REASON_EXCEPTION_NMI &&
+        is_nmi(tdexit_intr_info(vcpu))) {
+        kvm_before_interrupt(vcpu, KVM_HANDLING_NMI);
+        vmx_do_nmi_irqoff();
+        kvm_after_interrupt(vcpu);
+    }
     guest_state_exit_irqoff();
 }

> > > machine check and continue guest TD execution.
> > >
> > > For external interrupt, increment stats same to the VMX case.
> > >
> > > Signed-off-by: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
> > > Reviewed-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> > > ---
> > > arch/x86/kvm/vmx/tdx.c | 23 +++++++++++++++++++++++
> > > 1 file changed, 23 insertions(+)
> > >
> > > diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
> > > index 0db80fa020d2..bdd74682b474 100644
> > > --- a/arch/x86/kvm/vmx/tdx.c
> > > +++ b/arch/x86/kvm/vmx/tdx.c
> > > @@ -918,6 +918,25 @@ void tdx_handle_exit_irqoff(struct kvm_vcpu *vcpu)
> > > 		vmx_handle_exception_irqoff(vcpu, tdexit_intr_info(vcpu));
> > > }
> > >
> > > +static int tdx_handle_exception(struct kvm_vcpu *vcpu)

Should this function be named as tdx_handle_exception_nmi() since it's 
checking nmi as well?

> > > +{
> > > +	u32 intr_info = tdexit_intr_info(vcpu);
> > > +
> > > +	if (is_nmi(intr_info) || is_machine_check(intr_info))
> > > +		return 1;