[Qemu-devel] [PATCH v7 01/13] machine: Don't allow CPU toplogies with partially filled cores

[Bharata B Rao]

Prevent guests from booting with CPU topologies that have partially
filled CPU cores or can result in partially filled CPU cores after
CPU hotplug like

-smp 15,sockets=1,cores=4,threads=4,maxcpus=16 or
-smp 15,sockets=1,cores=4,threads=4,maxcpus=17.

This is enforced by introducing MachineClass::validate_smp_config()
that gets called from generic SMP parsing code. Machine type versions
that want to enforce this can define this to the generic version
provided.

Only sPAPR and PC machine types starting from version 2.6 enforce this in
this patch.

Signed-off-by: Bharata B Rao <address@hidden>
---
 hw/core/machine.c   | 23 +++++++++++++++++++++++
 hw/i386/pc.c        |  1 +
 hw/i386/pc_piix.c   |  1 +
 hw/i386/pc_q35.c    |  1 +
 hw/ppc/spapr.c      |  2 ++
 include/hw/boards.h |  4 ++++
 vl.c                |  5 +++++
 7 files changed, 37 insertions(+)

diff --git a/hw/core/machine.c b/hw/core/machine.c
index c46ddc7..4505995 100644
--- a/hw/core/machine.c
+++ b/hw/core/machine.c
@@ -336,6 +336,29 @@ static void machine_init_notify(Notifier *notifier, void 
*data)
     foreach_dynamic_sysbus_device(error_on_sysbus_device, NULL);
 }
 
+/*
+ * Machine types that want to prevent starting of guests with
+ * partially filled CPU cores can use this routine as their
+ * MachineClass:validate_smp_config().
+ */
+void validate_smp_config_generic(int smp_cpus, int max_cpus,
+                                 int smp_threads, Error **errp)
+{
+    if (smp_cpus % smp_threads) {
+        error_setg(errp, "cpu topology: "
+                   "smp_cpus (%u) should be multiple of threads (%u) ",
+                   smp_cpus, smp_threads);
+        return;
+    }
+
+    if (max_cpus % smp_threads) {
+        error_setg(errp, "cpu topology: "
+                   "max_cpus (%u) should be multiple of threads (%u) ",
+                   max_cpus, smp_threads);
+        return;
+    }
+}
+
 static void machine_class_init(ObjectClass *oc, void *data)
 {
     MachineClass *mc = MACHINE_CLASS(oc);
diff --git a/hw/i386/pc.c b/hw/i386/pc.c
index 78cf8fa..a54e0a0 100644
--- a/hw/i386/pc.c
+++ b/hw/i386/pc.c
@@ -1971,6 +1971,7 @@ static void pc_machine_class_init(ObjectClass *oc, void 
*data)
     mc->hot_add_cpu = pc_hot_add_cpu;
     mc->max_cpus = 255;
     mc->reset = pc_machine_reset;
+    mc->validate_smp_config = validate_smp_config_generic;
     hc->plug = pc_machine_device_plug_cb;
     hc->unplug_request = pc_machine_device_unplug_request_cb;
     hc->unplug = pc_machine_device_unplug_cb;
diff --git a/hw/i386/pc_piix.c b/hw/i386/pc_piix.c
index bc74557..98b8b69 100644
--- a/hw/i386/pc_piix.c
+++ b/hw/i386/pc_piix.c
@@ -435,6 +435,7 @@ static void pc_i440fx_2_5_machine_options(MachineClass *m)
     pc_i440fx_2_6_machine_options(m);
     m->alias = NULL;
     m->is_default = 0;
+    m->validate_smp_config = NULL;
     pcmc->save_tsc_khz = false;
     SET_MACHINE_COMPAT(m, PC_COMPAT_2_5);
 }
diff --git a/hw/i386/pc_q35.c b/hw/i386/pc_q35.c
index 6128b02..c5f4935 100644
--- a/hw/i386/pc_q35.c
+++ b/hw/i386/pc_q35.c
@@ -362,6 +362,7 @@ static void pc_q35_2_5_machine_options(MachineClass *m)
     PCMachineClass *pcmc = PC_MACHINE_CLASS(m);
     pc_q35_2_6_machine_options(m);
     m->alias = NULL;
+    m->validate_smp_config = NULL;
     pcmc->save_tsc_khz = false;
     SET_MACHINE_COMPAT(m, PC_COMPAT_2_5);
 }
diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index a9c9a95..6ac9f06 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -2317,6 +2317,7 @@ static void spapr_machine_class_init(ObjectClass *oc, 
void *data)
     mc->has_dynamic_sysbus = true;
     mc->pci_allow_0_address = true;
     mc->get_hotplug_handler = spapr_get_hotpug_handler;
+    mc->validate_smp_config = validate_smp_config_generic;
     hc->plug = spapr_machine_device_plug;
     hc->unplug = spapr_machine_device_unplug;
     mc->cpu_index_to_socket_id = spapr_cpu_index_to_socket_id;
@@ -2402,6 +2403,7 @@ static void spapr_machine_2_5_class_options(MachineClass 
*mc)
     spapr_machine_2_6_class_options(mc);
     smc->use_ohci_by_default = true;
     SET_MACHINE_COMPAT(mc, SPAPR_COMPAT_2_5);
+    mc->validate_smp_config = NULL;
 }
 
 DEFINE_SPAPR_MACHINE(2_5, "2.5", false);
diff --git a/include/hw/boards.h b/include/hw/boards.h
index 0f30959..435c339 100644
--- a/include/hw/boards.h
+++ b/include/hw/boards.h
@@ -40,6 +40,8 @@ int machine_kvm_shadow_mem(MachineState *machine);
 int machine_phandle_start(MachineState *machine);
 bool machine_dump_guest_core(MachineState *machine);
 bool machine_mem_merge(MachineState *machine);
+void validate_smp_config_generic(int smp_cpus, int max_cpus,
+                                 int smp_threads, Error **errp);
 
 /**
  * MachineClass:
@@ -99,6 +101,8 @@ struct MachineClass {
     HotplugHandler *(*get_hotplug_handler)(MachineState *machine,
                                            DeviceState *dev);
     unsigned (*cpu_index_to_socket_id)(unsigned cpu_index);
+    void (*validate_smp_config)(int smp_cpus, int max_cpus, int smp_threads,
+                                Error **errp);
 };
 
 /**
diff --git a/vl.c b/vl.c
index f043009..9e4da46 100644
--- a/vl.c
+++ b/vl.c
@@ -4126,6 +4126,11 @@ int main(int argc, char **argv, char **envp)
 
     smp_parse(qemu_opts_find(qemu_find_opts("smp-opts"), NULL));
 
+    if (machine_class->validate_smp_config) {
+        machine_class->validate_smp_config(smp_cpus, max_cpus, smp_threads,
+                                           &error_abort);
+    }
+
     machine_class->max_cpus = machine_class->max_cpus ?: 1; /* Default to UP */
     if (max_cpus > machine_class->max_cpus) {
         error_report("Number of SMP CPUs requested (%d) exceeds max CPUs "
-- 
2.1.0