[PATCH v4 1/6] x86: lpc9: let firmware negotiate 'CPU hotplug with SMI' features

[Igor Mammedov]

It will allow firmware to notify QEMU that firmware requires SMI
being triggered on CPU hot[un]plug, so that it would be able to account
for hotplugged CPU and relocate it to new SMM base and/or safely remove
CPU on unplug.

Using negotiated features, 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>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
---
v4:
  - fix 5.2 machine types so they won't apply pc_compat_5_1
     (Laszlo Ersek <lersek@redhat.com>)
v3:
  - rebase on top of "[PATCH v2] hw: add compat machines for 5.2"
    so apply that before this patch
v2:
  - rebase on top of 5.1 (move compat values to 5.1 machine)
  - make "x-smi-cpu-hotunplug" false by default (Laszlo Ersek 
<lersek@redhat.com>)

fixup
---
 include/hw/i386/ich9.h |  2 ++
 hw/i386/pc.c           |  4 +++-
 hw/isa/lpc_ich9.c      | 13 +++++++++++++
 3 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/include/hw/i386/ich9.h b/include/hw/i386/ich9.h
index a98d10b252..d1bb3f7bf0 100644
--- a/include/hw/i386/ich9.h
+++ b/include/hw/i386/ich9.h
@@ -247,5 +247,7 @@ 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
+#define ICH9_LPC_SMI_F_CPU_HOT_UNPLUG_BIT       2
 
 #endif /* HW_ICH9_H */
diff --git a/hw/i386/pc.c b/hw/i386/pc.c
index 9aa813949c..583db11d28 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_1[] = {};
+GlobalProperty pc_compat_5_1[] = {
+    { "ICH9-LPC", "x-smi-cpu-hotplug", "off" },
+};
 const size_t pc_compat_5_1_len = G_N_ELEMENTS(pc_compat_5_1);
 
 GlobalProperty pc_compat_5_0[] = {
diff --git a/hw/isa/lpc_ich9.c b/hw/isa/lpc_ich9.c
index cd6e169d47..19f32bed3e 100644
--- a/hw/isa/lpc_ich9.c
+++ b/hw/isa/lpc_ich9.c
@@ -373,6 +373,15 @@ 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) |
+                          BIT_ULL(ICH9_LPC_SMI_F_CPU_HOT_UNPLUG_BIT))) {
+        /*
+         * cpu hot-[un]plug with 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 +756,10 @@ 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_BIT64("x-smi-cpu-hotunplug", ICH9LPCState, smi_host_features,
+                      ICH9_LPC_SMI_F_CPU_HOT_UNPLUG_BIT, false),
     DEFINE_PROP_END_OF_LIST(),
 };
 
-- 
2.26.2