[PATCH v3 2/2] x86/svm: Use the virtual NMI when available

[Abdelkareem Abdelsaamad <abdelkareem.abdelsaamad@xxxxxxxxxx>]

With the Virtual NMI (vNMI), the pending NMI is simply stuffed into the VMCB
and handed off to the hardware. There is no need for the artificial tracking
of the NMI handling completion with the IRET instruction interception.

Adjust the svm_inject_nmi to rather inject the NMIs using the vNMI Hardware
accelerated feature when the AMD platform support the vNMI.

Adjust the svm_get_interrupt_shadow to check if the vNMI is currently blocked
by servicing another in-progress NMI.

Signed-off-by: Abdelkareem Abdelsaamad <abdelkareem.abdelsaamad@xxxxxxxxxx>
---
 xen/arch/x86/hvm/svm/intr.c | 9 +++++++++
 xen/arch/x86/hvm/svm/svm.c  | 5 ++++-
 xen/arch/x86/hvm/svm/vmcb.c | 2 ++
 3 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/xen/arch/x86/hvm/svm/intr.c b/xen/arch/x86/hvm/svm/intr.c
index 6453a46b85..3e8959f155 100644
--- a/xen/arch/x86/hvm/svm/intr.c
+++ b/xen/arch/x86/hvm/svm/intr.c
@@ -33,6 +33,15 @@ static void svm_inject_nmi(struct vcpu *v)
     u32 general1_intercepts = vmcb_get_general1_intercepts(vmcb);
     intinfo_t event;
 
+    if ( vmcb->_vintr.fields.vnmi_enable )
+    {
+       if ( !vmcb->_vintr.fields.vnmi_pending &&
+            !vmcb->_vintr.fields.vnmi_blocking )
+           vmcb->_vintr.fields.vnmi_pending = 1;
+
+        return;
+    }
+
     event.raw = 0;
     event.v = true;
     event.type = X86_ET_NMI;
diff --git a/xen/arch/x86/hvm/svm/svm.c b/xen/arch/x86/hvm/svm/svm.c
index 18ba837738..3dfdc18133 100644
--- a/xen/arch/x86/hvm/svm/svm.c
+++ b/xen/arch/x86/hvm/svm/svm.c
@@ -548,7 +548,9 @@ static unsigned cf_check int 
svm_get_interrupt_shadow(struct vcpu *v)
     if ( vmcb->int_stat.intr_shadow )
         intr_shadow |= HVM_INTR_SHADOW_MOV_SS | HVM_INTR_SHADOW_STI;
 
-    if ( vmcb_get_general1_intercepts(vmcb) & GENERAL1_INTERCEPT_IRET )
+    if ( vmcb->_vintr.fields.vnmi_enable
+         ? vmcb->_vintr.fields.vnmi_blocking
+         : (vmcb_get_general1_intercepts(vmcb) & GENERAL1_INTERCEPT_IRET) )
         intr_shadow |= HVM_INTR_SHADOW_NMI;
 
     return intr_shadow;
@@ -2524,6 +2526,7 @@ const struct hvm_function_table * __init start_svm(void)
     P(cpu_has_tsc_ratio, "TSC Rate MSR");
     P(cpu_has_svm_sss, "NPT Supervisor Shadow Stack");
     P(cpu_has_svm_spec_ctrl, "MSR_SPEC_CTRL virtualisation");
+    P(cpu_has_svm_vnmi, "Virtual NMI");
     P(cpu_has_svm_bus_lock, "Bus Lock Filter");
 #undef P
 
diff --git a/xen/arch/x86/hvm/svm/vmcb.c b/xen/arch/x86/hvm/svm/vmcb.c
index e583ef8548..e90bbac332 100644
--- a/xen/arch/x86/hvm/svm/vmcb.c
+++ b/xen/arch/x86/hvm/svm/vmcb.c
@@ -184,6 +184,8 @@ static int construct_vmcb(struct vcpu *v)
     if ( default_xen_spec_ctrl == SPEC_CTRL_STIBP )
         v->arch.msrs->spec_ctrl.raw = SPEC_CTRL_STIBP;
 
+    vmcb->_vintr.fields.vnmi_enable = cpu_has_svm_vnmi;
+
     return 0;
 }
 
-- 
2.52.0