[RFC PATCH 12/13] hw/acpi: disable modern CPU hotplug interface for mirror vcpu's

[Ashish Kalra]

From: Ashish Kalra <ashish.kalra@amd.com>

OVMF expects both fw_cfg and the modern CPU hotplug interface to
return the same boot CPU count. We reduce the fw_cfg boot cpu count
with number of mirror vcpus's. This fails the OVMF sanity check
as fw_cfg boot cpu count and modern CPU hotplug interface boot
count don't match, hence disable the modern CPU hotplug interface.

Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
---
 hw/acpi/cpu.c         | 11 ++++++++++-
 include/hw/acpi/cpu.h |  1 +
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/hw/acpi/cpu.c b/hw/acpi/cpu.c
index 8ac2fd018e..6cfaf2b450 100644
--- a/hw/acpi/cpu.c
+++ b/hw/acpi/cpu.c
@@ -86,7 +86,12 @@ static uint64_t cpu_hotplug_rd(void *opaque, hwaddr addr, 
unsigned size)
     case ACPI_CPU_CMD_DATA2_OFFSET_R:
         switch (cpu_st->command) {
         case CPHP_GET_NEXT_CPU_WITH_EVENT_CMD:
-           val = 0;
+           /* Disabling modern CPUHP interface for mirror vCPU support */
+           if (!cpu_st->mirror_vcpu_enabled) {
+               val = 0;
+           } else {
+               val = -1ULL;
+           }
            break;
         case CPHP_GET_CPU_ID_CMD:
            val = cdev->arch_id >> 32;
@@ -226,6 +231,10 @@ void cpu_hotplug_hw_init(MemoryRegion *as, Object *owner,
     state->dev_count = id_list->len;
     state->devs = g_new0(typeof(*state->devs), state->dev_count);
     for (i = 0; i < id_list->len; i++) {
+        /* Disabling modern CPUHP interface for mirror vCPU support */
+        if (id_list->cpus[i].mirror_vcpu) {
+            state->mirror_vcpu_enabled = TRUE;
+        }
         state->devs[i].cpu =  CPU(id_list->cpus[i].cpu);
         state->devs[i].arch_id = id_list->cpus[i].arch_id;
     }
diff --git a/include/hw/acpi/cpu.h b/include/hw/acpi/cpu.h
index 999caaf510..e7949e86b8 100644
--- a/include/hw/acpi/cpu.h
+++ b/include/hw/acpi/cpu.h
@@ -33,6 +33,7 @@ typedef struct CPUHotplugState {
     uint8_t command;
     uint32_t dev_count;
     AcpiCpuStatus *devs;
+    bool mirror_vcpu_enabled;
 } CPUHotplugState;
 
 void acpi_cpu_plug_cb(HotplugHandler *hotplug_dev,
-- 
2.17.1