Re: [PATCH 1/2] KVM: TDX: Enable Notify VM exit

[Sean Christopherson <seanjc@google.com>]

On Fri, Aug 07, 2026, Xiaoyao Li wrote:
> On 8/6/2026 9:33 PM, Nikolay Borisov wrote:
> > > diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
> > > index 545b03d9d10b..cdc0d24657ac 100644
> > > --- a/arch/x86/kvm/vmx/tdx.c
> > > +++ b/arch/x86/kvm/vmx/tdx.c
> > > @@ -2129,6 +2129,9 @@ int tdx_handle_exit(struct kvm_vcpu *vcpu,
> > > fastpath_t fastpath)
> > >            * - If it's not an MSMI, no need to do anything here.
> > >            */
> > >           return 1;
> > > +    case EXIT_REASON_NOTIFY:
> > > +        /* NMI blocking state is handled by TDX module */
> > > +        return __handle_notify(vcpu, false);
> > 
> > I'd rather there be a private handle_tdx_notify function in tdx.c than
> > exposing __handle_notify and introducing the boolean. This is needed
> > because the TDX module handles the NMI unblocking, so let's keep the
> > implementation specific to tdx.
> 
> The initial version just implemented a separate handler for TDX. It had the
> exact same code as VMX's handle_notify() except the "NMI blocking handling".
> So to eliminate the code duplication, I changed to current code.
> 
> Sean, please let me if you have a preference. Otherwise, I'll follow
> Nikolay's preference in a v2.

Handling this like __vmx_handle_ept_violation() and __vmx_deliver_posted_interrupt()
seems like the obvious answer.

diff --git a/arch/x86/kvm/vmx/common.h b/arch/x86/kvm/vmx/common.h
index 08005676702c..c179fb34c336 100644
--- a/arch/x86/kvm/vmx/common.h
+++ b/arch/x86/kvm/vmx/common.h
@@ -4,6 +4,7 @@
 
 #include <linux/kvm_host.h>
 #include <asm/posted_intr.h>
+#include <asm/vmx.h>
 
 #include "mmu.h"
 
@@ -183,6 +184,25 @@ static inline void __vmx_deliver_posted_interrupt(struct kvm_vcpu *vcpu,
        kvm_vcpu_trigger_posted_interrupt(vcpu, POSTED_INTR_VECTOR);
 }
 
+static inline int __vmx_handle_notify(struct kvm_vcpu *vcpu,
+                                     unsigned long exit_qual)
+{
+
+       bool context_invalid = exit_qual & NOTIFY_VM_CONTEXT_INVALID;
+
+       ++vcpu->stat.notify_window_exits;
+
+       if (vcpu->kvm->arch.notify_vmexit_flags & KVM_X86_NOTIFY_VMEXIT_USER ||
+           context_invalid) {
+               vcpu->run->exit_reason = KVM_EXIT_NOTIFY;
+               vcpu->run->notify.flags = context_invalid ?
+                                         KVM_NOTIFY_CONTEXT_INVALID : 0;
+               return 0;
+       }
+
+       return 1;
+}
+
 noinstr void vmx_handle_nmi(struct kvm_vcpu *vcpu);
 
 #endif /* __KVM_X86_VMX_COMMON_H */
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 9abd2ed3aeae..e77c1037e95d 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -6289,9 +6289,6 @@ static int handle_bus_lock_vmexit(struct kvm_vcpu *vcpu)
 static int handle_notify(struct kvm_vcpu *vcpu)
 {
        unsigned long exit_qual = vmx_get_exit_qual(vcpu);
-       bool context_invalid = exit_qual & NOTIFY_VM_CONTEXT_INVALID;
-
-       ++vcpu->stat.notify_window_exits;
 
        /*
         * Notify VM exit happened while executing iret from NMI,
@@ -6301,15 +6298,7 @@ static int handle_notify(struct kvm_vcpu *vcpu)
                vmcs_set_bits(GUEST_INTERRUPTIBILITY_INFO,
                              GUEST_INTR_STATE_NMI);
 
-       if (vcpu->kvm->arch.notify_vmexit_flags & KVM_X86_NOTIFY_VMEXIT_USER ||
-           context_invalid) {
-               vcpu->run->exit_reason = KVM_EXIT_NOTIFY;
-               vcpu->run->notify.flags = context_invalid ?
-                                         KVM_NOTIFY_CONTEXT_INVALID : 0;
-               return 0;
-       }
-
-       return 1;
+       return __vmx_handle_notify(vcpu, exit_qual);
 }
 
 static int vmx_get_msr_imm_reg(struct kvm_vcpu *vcpu)