[Xen-devel] [PATCH] x86/hvm: Add per-vcpu evtchn upcalls

[Paul Durrant <paul.durrant@xxxxxxxxxx>]

HVM guests have always been confined to using the domain callback
via (see HVM_PARAM_CALLBACK_IRQ) to receive event notifications
which is an IOAPIC vector and is only used if the event channel is
bound to vcpu 0.
This patch adds a new HVM op allowing a guest to specify a local
APIC vector to use as an upcall notification for a specific vcpu.
This therefore allows a guest which sets a vector for a vcpu
other than 0 to then bind event channels to that vcpu.

Signed-off-by: Paul Durrant <paul.durrant@xxxxxxxxxx>
Cc: Keir Fraser <keir@xxxxxxx>
Cc: Jan Beulich <jbeulich@xxxxxxxx>
---
 xen/arch/x86/hvm/hvm.c          |   35 +++++++++++++++++++++++++++++++++++
 xen/arch/x86/hvm/irq.c          |    9 +++++++++
 xen/include/asm-x86/hvm/vcpu.h  |    1 +
 xen/include/public/hvm/hvm_op.h |   16 ++++++++++++++++
 4 files changed, 61 insertions(+)

diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index 78f519d..684e666 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -5458,6 +5458,36 @@ static int hvmop_destroy_ioreq_server(
     return rc;
 }
 
+static int hvmop_set_evtchn_upcall_vector(
+    XEN_GUEST_HANDLE_PARAM(xen_hvm_set_evtchn_upcall_vector_t) uop)
+{
+    xen_hvm_set_evtchn_upcall_vector_t op;
+    struct domain *d;
+    struct vcpu *v;
+    int rc;
+
+    if ( copy_from_guest(&op, uop, 1) )
+        return -EFAULT;
+
+    d = rcu_lock_current_domain();
+
+    rc = -EINVAL;
+    if ( !is_hvm_domain(d) )
+        goto out;
+
+    if ( op.vcpu >= d->max_vcpus || (v = d->vcpu[op.vcpu]) == NULL )
+        goto out;
+
+    printk(XENLOG_G_INFO "%pv: %s %u\n", v, __func__, op.vector);
+
+    v->arch.hvm_vcpu.evtchn_upcall_vector = op.vector;
+    rc = 0;
+
+ out:
+    rcu_unlock_domain(d);
+    return rc;
+}
+
 #define HVMOP_op_mask 0xff
 
 long do_hvm_op(unsigned long op, XEN_GUEST_HANDLE_PARAM(void) arg)
@@ -5499,6 +5529,11 @@ long do_hvm_op(unsigned long op, 
XEN_GUEST_HANDLE_PARAM(void) arg)
             guest_handle_cast(arg, xen_hvm_destroy_ioreq_server_t));
         break;
     
+    case HVMOP_set_evtchn_upcall_vector:
+        rc = hvmop_set_evtchn_upcall_vector(
+            guest_handle_cast(arg, xen_hvm_set_evtchn_upcall_vector_t));
+        break;
+    
     case HVMOP_set_param:
     case HVMOP_get_param:
     {
diff --git a/xen/arch/x86/hvm/irq.c b/xen/arch/x86/hvm/irq.c
index 35f4f94..3e4c0b4 100644
--- a/xen/arch/x86/hvm/irq.c
+++ b/xen/arch/x86/hvm/irq.c
@@ -152,6 +152,13 @@ void hvm_isa_irq_deassert(
     spin_unlock(&d->arch.hvm_domain.irq_lock);
 }
 
+static void hvm_set_upcall_irq(struct vcpu *v)
+{
+    uint8_t vector = v->arch.hvm_vcpu.evtchn_upcall_vector;
+
+    vlapic_set_irq(vcpu_vlapic(v), vector, 0);
+}
+
 static void hvm_set_callback_irq_level(struct vcpu *v)
 {
     struct domain *d = v->domain;
@@ -220,6 +227,8 @@ void hvm_assert_evtchn_irq(struct vcpu *v)
 
     if ( is_hvm_pv_evtchn_vcpu(v) )
         vcpu_kick(v);
+    else if ( v->arch.hvm_vcpu.evtchn_upcall_vector != 0 )
+        hvm_set_upcall_irq(v);
     else if ( v->vcpu_id == 0 )
         hvm_set_callback_irq_level(v);
 }
diff --git a/xen/include/asm-x86/hvm/vcpu.h b/xen/include/asm-x86/hvm/vcpu.h
index 01e0665..edd4523 100644
--- a/xen/include/asm-x86/hvm/vcpu.h
+++ b/xen/include/asm-x86/hvm/vcpu.h
@@ -160,6 +160,7 @@ struct hvm_vcpu {
     } u;
 
     struct tasklet      assert_evtchn_irq_tasklet;
+    u8                  evtchn_upcall_vector;
 
     struct nestedvcpu   nvcpu;
 
diff --git a/xen/include/public/hvm/hvm_op.h b/xen/include/public/hvm/hvm_op.h
index eeb0a60..33ccf45 100644
--- a/xen/include/public/hvm/hvm_op.h
+++ b/xen/include/public/hvm/hvm_op.h
@@ -369,6 +369,22 @@ DEFINE_XEN_GUEST_HANDLE(xen_hvm_set_ioreq_server_state_t);
 
 #endif /* defined(__XEN__) || defined(__XEN_TOOLS__) */
 
+/*
+ * HVMOP_set_evtchn_upcall_vector: Set a <vector> that should be used for event
+ *                                 channel upcalls on the specified <vcpu>. If 
set,
+ *                                 this vector will be used in preference to 
the
+ *                                 domain callback via (see 
HVM_PARAM_CALLBACK_IRQ)
+ *                                 and hence allows HVM guests to bind event
+ *                                 event channels to a vcpu other than 0.
+ */
+#define HVMOP_set_evtchn_upcall_vector 23
+struct xen_hvm_set_evtchn_upcall_vector {
+    uint32_t vcpu;
+    uint8_t vector;
+};
+typedef struct xen_hvm_set_evtchn_upcall_vector 
xen_hvm_set_evtchn_upcall_vector_t;
+DEFINE_XEN_GUEST_HANDLE(xen_hvm_set_evtchn_upcall_vector_t);
+
 #endif /* __XEN_PUBLIC_HVM_HVM_OP_H__ */
 
 /*
-- 
1.7.10.4


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