arm/virt: Support CPU cold plug

This adds CPU cold plug support to arm virt machine board.
CPU cold plug means adding CPU by using "-device xx-arm-cpu"
when we bring up Qemu.

Signed-off-by: Keqian Zhu <zhukeqian1@huawei.com>

arm-virt-Support-CPU-cold-plug.patch

@@ -0,0 +1,92 @@
+From e3a1af72fca5bbcc840fba44d512bbe69ec55ca9 Mon Sep 17 00:00:00 2001
+From: Keqian Zhu <zhukeqian1@huawei.com>
+Date: Tue, 12 May 2020 15:05:06 +0800
+Subject: [PATCH] arm/virt: Support CPU cold plug
+
+This adds CPU cold plug support to arm virt machine board.
+CPU cold plug means adding CPU by using "-device xx-arm-cpu"
+when we bring up Qemu.
+
+Signed-off-by: Keqian Zhu <zhukeqian1@huawei.com>
+---
+ hw/arm/virt.c | 36 +++++++++++++++++++-----------------
+ 1 file changed, 19 insertions(+), 17 deletions(-)
+
+diff --git a/hw/arm/virt.c b/hw/arm/virt.c
+index 112a6ae7cb..4c7279392f 100644
+--- a/hw/arm/virt.c
++++ b/hw/arm/virt.c
+@@ -2093,25 +2093,12 @@ static void virt_cpu_pre_plug(HotplugHandler *hotplug_dev,
+     int smp_cores = ms->smp.cores;
+     int smp_threads = ms->smp.threads;
+ 
+-    /* Some hotplug capability checks */
+-
+     if (!object_dynamic_cast(OBJECT(cpu), ms->cpu_type)) {
+         error_setg(errp, "Invalid CPU type, expected cpu type: '%s'",
+                    ms->cpu_type);
+         return;
+     }
+ 
+-    if (dev->hotplugged && !vms->acpi_dev) {
+-        error_setg(errp, "CPU hotplug is disabled: missing acpi device.");
+-        return;
+-    }
+-
+-    if (dev->hotplugged && !vms->cpu_hotplug_enabled) {
+-        error_setg(errp, "CPU hotplug is disabled: "
+-                         "should use AArch64 CPU and GICv3.");
+-        return;
+-    }
+-
+     /* if cpu idx is not set, set it based on socket/core/thread properties */
+     if (cs->cpu_index == UNASSIGNED_CPU_INDEX) {
+         int max_socket = ms->smp.max_cpus / smp_threads / smp_cores;
+@@ -2137,6 +2124,20 @@ static void virt_cpu_pre_plug(HotplugHandler *hotplug_dev,
+         cs->cpu_index = idx_from_topo_ids(smp_cores, smp_threads, &topo);
+     }
+ 
++    /* Some hotplug capability checks */
++    if (cs->cpu_index >= ms->smp.cpus) {
++        if (!vms->acpi_dev) {
++            error_setg(errp, "CPU cold/hot plug is disabled: "
++                             "missing acpi device.");
++            return;
++        }
++        if (!vms->cpu_hotplug_enabled) {
++            error_setg(errp, "CPU cold/hot plug is disabled: "
++                             "should use AArch64 CPU and GICv3.");
++            return;
++        }
++    }
++
+     /* if 'address' properties socket-id/core-id/thread-id are not set, set them
+      * so that machine_query_hotpluggable_cpus would show correct values
+      */
+@@ -2237,7 +2238,8 @@ static void virt_cpu_plug(HotplugHandler *hotplug_dev,
+     ARMGICv3CommonClass *agcc;
+     Error *local_err = NULL;
+ 
+-    if (dev->hotplugged) {
++    /* For CPU that is cold/hot plugged */
++    if (ncpu >= ms->smp.cpus) {
+         /* Realize GIC related parts of CPU */
+         assert(vms->gic_version == 3);
+         gicv3 = ARM_GICV3_COMMON(vms->gic);
+@@ -2250,10 +2252,10 @@ static void virt_cpu_plug(HotplugHandler *hotplug_dev,
+         cpu_hotplug_register_reset(ncpu);
+         cpu_hotplug_reset_manually(ncpu);
+         cpu_synchronize_post_reset(cs);
++    }
+ 
+-        if (kvm_enabled()) {
+-            resume_all_vcpus();
+-        }
++    if (dev->hotplugged && kvm_enabled()) {
++        resume_all_vcpus();
+     }
+ 
+     if (vms->acpi_dev) {
+-- 
+2.19.1
+

qemu.spec

@@ -161,6 +161,7 @@ Patch0148: vtimer-compat-cross-version-migration-from-v4.0.1.patch
 Patch0149: migration-ram-Do-error_free-after-migrate_set_error-.patch
 Patch0150: migration-ram-fix-memleaks-in-multifd_new_send_chann.patch
 Patch0151: migration-rdma-fix-a-memleak-on-error-path-in-rdma_s.patch
+Patch0152: arm-virt-Support-CPU-cold-plug.patch
 
 BuildRequires: flex
 BuildRequires: bison
@@ -506,6 +507,9 @@ getent passwd qemu >/dev/null || \
 %endif
 
 %changelog
+* Tue May 12 2020 Huawei Technologies Co., Ltd. <zhukeqian1@huawei.com>
+- arm/virt: Support CPU cold plug
+
 * Sat May 9 2020 Huawei Technologies Co., Ltd. <pannengyuan@huawei.com>
 - migration/ram: do error_free after migrate_set_error to avoid memleaks.
 - migration/ram: fix memleaks in multifd_new_send_channel_async.