[PATCH 1/3] xen/vioapic: add support for the extended destination ID field

[Roger Pau Monne <roger.pau@xxxxxxxxxx>]

Such field uses bits 55:48, but for the purposes the register will be
used use bits 55:49 instead. Bit 48 is used to signal an RTE entry is
in remappable format which is not supported by the vIO-APIC.

Use the extended destination ID to store the high bits from the
destination ID, thus expanding the size of the destination ID field to
15 bits, allowing an IO-APIC to target APIC IDs up to 32768.

Note this is already supported by QEMU/KVM and HyperV.

Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
---
 xen/arch/x86/hvm/vioapic.c             | 3 ++-
 xen/include/public/arch-x86/hvm/save.h | 4 +++-
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/xen/arch/x86/hvm/vioapic.c b/xen/arch/x86/hvm/vioapic.c
index 553c0f76ef..1f2305c232 100644
--- a/xen/arch/x86/hvm/vioapic.c
+++ b/xen/arch/x86/hvm/vioapic.c
@@ -412,7 +412,8 @@ static void ioapic_inj_irq(
 
 static void vioapic_deliver(struct hvm_vioapic *vioapic, unsigned int pin)
 {
-    uint16_t dest = vioapic->redirtbl[pin].fields.dest_id;
+    uint16_t dest = vioapic->redirtbl[pin].fields.dest_id |
+                    (vioapic->redirtbl[pin].fields.ext_dest_id << 8);
     uint8_t dest_mode = vioapic->redirtbl[pin].fields.dest_mode;
     uint8_t delivery_mode = vioapic->redirtbl[pin].fields.delivery_mode;
     uint8_t vector = vioapic->redirtbl[pin].fields.vector;
diff --git a/xen/include/public/arch-x86/hvm/save.h 
b/xen/include/public/arch-x86/hvm/save.h
index 773a380bc2..14a5d94588 100644
--- a/xen/include/public/arch-x86/hvm/save.h
+++ b/xen/include/public/arch-x86/hvm/save.h
@@ -376,7 +376,9 @@ union vioapic_redir_entry
         uint8_t trig_mode:1;
         uint8_t mask:1;
         uint8_t reserve:7;
-        uint8_t reserved[4];
+        uint8_t reserved[3];
+        uint8_t :1;
+        uint8_t ext_dest_id:7;
         uint8_t dest_id;
     } fields;
 };
-- 
2.34.1