[RFC 1/3] x86: lpc9: let firmware negotiate CPU hotplug SMI feature

[Igor Mammedov]

It will allow firmware to notify QEMU that firmware requires SMI
being triggered on CPU hotplug, so that it would be able to account
for hotplugged CPU and relocate it to new SMM base.

Using the negotiated feature, follow up patches will insert SMI upcall
into AML code, to make sure that firmware processes hotplug before
guest OS would attempt to use new CPU.

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
---
 include/hw/i386/ich9.h | 1 +
 hw/i386/pc.c           | 4 +++-
 hw/isa/lpc_ich9.c      | 7 +++++++
 3 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/include/hw/i386/ich9.h b/include/hw/i386/ich9.h
index a98d10b252..422891a152 100644
--- a/include/hw/i386/ich9.h
+++ b/include/hw/i386/ich9.h
@@ -247,5 +247,6 @@ typedef struct ICH9LPCState {
 
 /* bit positions used in fw_cfg SMI feature negotiation */
 #define ICH9_LPC_SMI_F_BROADCAST_BIT            0
+#define ICH9_LPC_SMI_F_CPU_HOTPLUG_BIT          1
 
 #endif /* HW_ICH9_H */
diff --git a/hw/i386/pc.c b/hw/i386/pc.c
index d7f27bc16b..6fe80c84d7 100644
--- a/hw/i386/pc.c
+++ b/hw/i386/pc.c
@@ -97,7 +97,9 @@
 #include "fw_cfg.h"
 #include "trace.h"
 
-GlobalProperty pc_compat_5_0[] = {};
+GlobalProperty pc_compat_5_0[] = {
+    { "ICH9-LPC", "x-smi-cpu-hotplug", "off" },
+};
 const size_t pc_compat_5_0_len = G_N_ELEMENTS(pc_compat_5_0);
 
 GlobalProperty pc_compat_4_2[] = {
diff --git a/hw/isa/lpc_ich9.c b/hw/isa/lpc_ich9.c
index cd6e169d47..83da7346ab 100644
--- a/hw/isa/lpc_ich9.c
+++ b/hw/isa/lpc_ich9.c
@@ -373,6 +373,11 @@ static void smi_features_ok_callback(void *opaque)
         /* guest requests invalid features, leave @features_ok at zero */
         return;
     }
+    if (!(guest_features & BIT_ULL(ICH9_LPC_SMI_F_BROADCAST_BIT)) &&
+        guest_features & BIT_ULL(ICH9_LPC_SMI_F_CPU_HOTPLUG_BIT)) {
+        /* cpu hotplug SMI requires SMI broadcast, leave @features_ok at zero 
*/
+        return;
+    }
 
     /* valid feature subset requested, lock it down, report success */
     lpc->smi_negotiated_features = guest_features;
@@ -747,6 +752,8 @@ static Property ich9_lpc_properties[] = {
     DEFINE_PROP_BOOL("noreboot", ICH9LPCState, pin_strap.spkr_hi, true),
     DEFINE_PROP_BIT64("x-smi-broadcast", ICH9LPCState, smi_host_features,
                       ICH9_LPC_SMI_F_BROADCAST_BIT, true),
+    DEFINE_PROP_BIT64("x-smi-cpu-hotplug", ICH9LPCState, smi_host_features,
+                      ICH9_LPC_SMI_F_CPU_HOTPLUG_BIT, true),
     DEFINE_PROP_END_OF_LIST(),
 };
 
-- 
2.26.2