x86/xen: event channels delivery on HVM.

Set the callback to receive evtchns from Xen, using the
callback vector delivery mechanism.

The traditional way for receiving event channel notifications from Xen
is via the interrupts from the platform PCI device.
The callback vector is a newer alternative that allow us to receive
notifications on any vcpu and doesn't need any PCI support: we allocate
a vector exclusively to receive events, in the vector handler we don't
need to interact with the vlapic, therefore we avoid a VMEXIT.

Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Signed-off-by: Sheng Yang <sheng@linux.intel.com>
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>

3 files changed, 16 insertions, 0 deletions

diff --git a/include/xen/events.h b/include/xen/events.h
index e68d59a90ca8..a15d93262e30 100644
--- a/include/xen/events.h
+++ b/include/xen/events.h
@@ -56,4 +56,11 @@ void xen_poll_irq(int irq);
 /* Determine the IRQ which is bound to an event channel */
 unsigned irq_from_evtchn(unsigned int evtchn);
 
+/* Xen HVM evtchn vector callback */
+extern void xen_hvm_callback_vector(void);
+extern int xen_have_vector_callback;
+int xen_set_callback_via(uint64_t via);
+void xen_evtchn_do_upcall(struct pt_regs *regs);
+void xen_hvm_evtchn_do_upcall(void);
+
 #endif  /* _XEN_EVENTS_H */
diff --git a/include/xen/hvm.h b/include/xen/hvm.h
index 5dfe8fb86e67..b193fa2f9fdd 100644
--- a/include/xen/hvm.h
+++ b/include/xen/hvm.h
@@ -3,6 +3,7 @@
 #define XEN_HVM_H__
 
 #include <xen/interface/hvm/params.h>
+#include <asm/xen/hypercall.h>
 
 static inline int hvm_get_parameter(int idx, uint64_t *value)
 {
@@ -21,4 +22,9 @@ static inline int hvm_get_parameter(int idx, uint64_t *value)
         return r;
 }
 
+#define HVM_CALLBACK_VIA_TYPE_VECTOR 0x2
+#define HVM_CALLBACK_VIA_TYPE_SHIFT 56
+#define HVM_CALLBACK_VECTOR(x) (((uint64_t)HVM_CALLBACK_VIA_TYPE_VECTOR)<<\
+                HVM_CALLBACK_VIA_TYPE_SHIFT | (x))
+
 #endif /* XEN_HVM_H__ */
diff --git a/include/xen/interface/features.h b/include/xen/interface/features.h
index f51b6413b054..8ab08b91bf6f 100644
--- a/include/xen/interface/features.h
+++ b/include/xen/interface/features.h
@@ -41,6 +41,9 @@
 /* x86: Does this Xen host support the MMU_PT_UPDATE_PRESERVE_AD hypercall? */
 #define XENFEAT_mmu_pt_update_preserve_ad  5
 
+/* x86: Does this Xen host support the HVM callback vector type? */
+#define XENFEAT_hvm_callback_vector        8
+
 #define XENFEAT_NR_SUBMAPS 1
 
 #endif /* __XEN_PUBLIC_FEATURES_H__ */