[PATCH 3/3] svm/vnmi: Add support for the SVM Virtual NMI

[Abdelkareem@xxxxxxxxx, Abdelsaamad@xxxxxxxxx, abdelkareem.abdelsaamad@xxxxxxxxxx]

From: Abdelkareem Abdelsaamad <abdelkareem.abdelsaamad@xxxxxxxxxx>

With vNMI, the pending NMI is simply stuffed into the VMCB and handed off
to the hardware. This means that Xen needs to be able to set a vNMI pending
on-demand, and also query if a vNMI is pending, e.g. to honor the "at most
one NMI pending" rule and to preserve all NMIs across save and restore.

Introduce two new hvm_function_table callbacks to support the SVM's vNMI to
allow the Xen hypervisor to query if a vNMI is pending and to set VMCB's
_vintr pending flag so the NMIs are serviced by hardware if/when the virtual
NMIs become unblocked.

Signed-off-by: Abdelkareem Abdelsaamad <abdelkareem.abdelsaamad@xxxxxxxxxx>
---
 xen/arch/x86/hvm/hvm.c             | 29 +++++++++++++++++++++--------
 xen/arch/x86/hvm/svm/intr.c        | 16 ++++++++++++++--
 xen/arch/x86/hvm/svm/svm.c         | 23 ++++++++++++++++++++++-
 xen/arch/x86/hvm/svm/vmcb.c        |  3 +++
 xen/arch/x86/include/asm/hvm/hvm.h |  8 ++++++++
 5 files changed, 68 insertions(+), 11 deletions(-)

diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index 4d37a93c57..3117ef8f2f 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -3904,10 +3904,29 @@ void hvm_ud_intercept(struct cpu_user_regs *regs)
     }
 }
 
-enum hvm_intblk hvm_interrupt_blocked(struct vcpu *v, struct hvm_intack intack)
+static enum hvm_intblk hvm_nmi_blocked(struct vcpu *v)
 {
     unsigned long intr_shadow;
 
+    if (hvm_funcs.caps.vNMI)
+    {
+        if (!hvm_funcs.is_vnmi_pending(v))
+            return hvm_intblk_none;
+
+        return hvm_intblk_vnmi;
+    }
+
+    intr_shadow = alternative_call(hvm_funcs.get_interrupt_shadow, v);
+
+    if ( intr_shadow & (HVM_INTR_SHADOW_STI|HVM_INTR_SHADOW_MOV_SS) )
+        return hvm_intblk_shadow;
+
+    return ((intr_shadow & HVM_INTR_SHADOW_NMI) ?
+            hvm_intblk_nmi_iret : hvm_intblk_none);
+}
+
+enum hvm_intblk hvm_interrupt_blocked(struct vcpu *v, struct hvm_intack intack)
+{
     ASSERT(v == current);
 
     if ( nestedhvm_enabled(v->domain) ) {
@@ -3922,14 +3941,8 @@ enum hvm_intblk hvm_interrupt_blocked(struct vcpu *v, 
struct hvm_intack intack)
          !(guest_cpu_user_regs()->eflags & X86_EFLAGS_IF) )
         return hvm_intblk_rflags_ie;
 
-    intr_shadow = alternative_call(hvm_funcs.get_interrupt_shadow, v);
-
-    if ( intr_shadow & (HVM_INTR_SHADOW_STI|HVM_INTR_SHADOW_MOV_SS) )
-        return hvm_intblk_shadow;
-
     if ( intack.source == hvm_intsrc_nmi )
-        return ((intr_shadow & HVM_INTR_SHADOW_NMI) ?
-                hvm_intblk_nmi_iret : hvm_intblk_none);
+        return hvm_nmi_blocked(v);
 
     if ( intack.source == hvm_intsrc_lapic )
     {
diff --git a/xen/arch/x86/hvm/svm/intr.c b/xen/arch/x86/hvm/svm/intr.c
index 6453a46b85..c54298c402 100644
--- a/xen/arch/x86/hvm/svm/intr.c
+++ b/xen/arch/x86/hvm/svm/intr.c
@@ -29,10 +29,19 @@
 
 static void svm_inject_nmi(struct vcpu *v)
 {
-    struct vmcb_struct *vmcb = v->arch.hvm.svm.vmcb;
-    u32 general1_intercepts = vmcb_get_general1_intercepts(vmcb);
+    struct vmcb_struct *vmcb;
+    u32 general1_intercepts;
     intinfo_t event;
 
+    if (hvm_funcs.caps.vNMI)
+    {
+        hvm_funcs.set_vnmi_pending(v);
+        return;
+    }
+
+    vmcb = v->arch.hvm.svm.vmcb;
+    general1_intercepts = vmcb_get_general1_intercepts(vmcb);
+
     event.raw = 0;
     event.v = true;
     event.type = X86_ET_NMI;
@@ -176,6 +185,9 @@ void asmlinkage svm_intr_assist(void)
             }
         }
 
+        // vNMI is currently serviced in progress.
+        if (unlikely(intblk == hvm_intblk_vnmi)) return;
+
         /*
          * Pending IRQs must be delayed if:
          * 1. An event is already pending. This is despite the fact that SVM
diff --git a/xen/arch/x86/hvm/svm/svm.c b/xen/arch/x86/hvm/svm/svm.c
index e451937b04..f67869353b 100644
--- a/xen/arch/x86/hvm/svm/svm.c
+++ b/xen/arch/x86/hvm/svm/svm.c
@@ -297,6 +297,26 @@ void svm_intercept_msr(struct vcpu *v, uint32_t msr, int 
flags)
         __clear_bit(msr * 2 + 1, msr_bit);
 }
 
+static bool cf_check svm_is_vnmi_pending(struct vcpu *vcpu)
+{
+    if (!hvm_funcs.caps.vNMI)
+        return false;
+
+    return (vcpu->arch.hvm.svm.vmcb->_vintr.fields.vnmi_blocking);
+}
+
+static bool cf_check svm_set_vnmi_pending(struct vcpu *vcpu)
+{
+    if (!hvm_funcs.caps.vNMI)
+        return false;
+
+    if (vcpu->arch.hvm.svm.vmcb->_vintr.fields.vnmi_pending)
+        return false;
+
+    vcpu->arch.hvm.svm.vmcb->_vintr.fields.vnmi_pending = 1;
+    return true;
+}
+
 #ifdef CONFIG_VM_EVENT
 static void cf_check svm_enable_msr_interception(struct domain *d, uint32_t 
msr)
 {
@@ -2464,7 +2484,8 @@ static struct hvm_function_table __initdata_cf_clobber 
svm_function_table = {
 #endif
     .set_rdtsc_exiting    = svm_set_rdtsc_exiting,
     .get_insn_bytes       = svm_get_insn_bytes,
-
+    .is_vnmi_pending = svm_is_vnmi_pending,
+    .set_vnmi_pending = svm_set_vnmi_pending,
     .nhvm_vcpu_initialise = nsvm_vcpu_initialise,
     .nhvm_vcpu_destroy = nsvm_vcpu_destroy,
     .nhvm_vcpu_reset = nsvm_vcpu_reset,
diff --git a/xen/arch/x86/hvm/svm/vmcb.c b/xen/arch/x86/hvm/svm/vmcb.c
index e583ef8548..5069789f6c 100644
--- a/xen/arch/x86/hvm/svm/vmcb.c
+++ b/xen/arch/x86/hvm/svm/vmcb.c
@@ -184,6 +184,9 @@ static int construct_vmcb(struct vcpu *v)
     if ( default_xen_spec_ctrl == SPEC_CTRL_STIBP )
         v->arch.msrs->spec_ctrl.raw = SPEC_CTRL_STIBP;
 
+    if (hvm_funcs.caps.vNMI)
+        vmcb->_vintr.fields.vnmi_enable = 1;
+
     return 0;
 }
 
diff --git a/xen/arch/x86/include/asm/hvm/hvm.h 
b/xen/arch/x86/include/asm/hvm/hvm.h
index ad17ea73e9..d7f439d41b 100644
--- a/xen/arch/x86/include/asm/hvm/hvm.h
+++ b/xen/arch/x86/include/asm/hvm/hvm.h
@@ -67,6 +67,7 @@ enum hvm_intblk {
     hvm_intblk_rflags_ie, /* RFLAGS.IE == 0 */
     hvm_intblk_tpr,       /* LAPIC TPR too high */
     hvm_intblk_nmi_iret,  /* NMI blocked until IRET */
+    hvm_intblk_vnmi,      /* vNMI is currently blocked*/
     hvm_intblk_arch,      /* SVM/VMX specific reason */
 };
 
@@ -224,6 +225,13 @@ struct hvm_function_table {
     int (*pi_update_irte)(const struct vcpu *v, const struct pirq *pirq,
                           uint8_t gvec);
     void (*update_vlapic_mode)(struct vcpu *v);
+    /* Whether or not a virtual NMI is pending in hardware. */
+    bool (*is_vnmi_pending)(struct vcpu *vcpu);
+    /*
+     * Attempt to pend a virtual NMI in harware.
+     * Returns %true on success
+     */
+    bool (*set_vnmi_pending)(struct vcpu *vcpu);
 
     /*Walk nested p2m  */
     int (*nhvm_hap_walk_L1_p2m)(struct vcpu *v, paddr_t L2_gpa,
-- 
2.52.0