cxl: Machine level control on whether CXL support is enabled

There are going to be some potential overheads to CXL enablement,
for example the host bridge region reserved in memory maps.
Add a machine level control so that CXL is disabled by default.

Signed-off-by: Jonathan Cameron <jonathan.cameron@huawei.com>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Message-Id: <20220429144110.25167-14-Jonathan.Cameron@huawei.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

diff --git a/hw/core/machine.c b/hw/core/machine.c
index 3264c1e11df4b13ce8a1ea3a5b8a2076d13eda37..b03d9192bafbdbc24c0e2d754da9baf923b00a64 100644 (file)
--- a/hw/core/machine.c
+++ b/hw/core/machine.c
@@ -33,6 +33,7 @@
 #include "sysemu/qtest.h"
 #include "hw/pci/pci.h"
 #include "hw/mem/nvdimm.h"
+#include "hw/cxl/cxl.h"
 #include "migration/global_state.h"
 #include "migration/vmstate.h"
 #include "exec/confidential-guest-support.h"
@@ -625,6 +626,20 @@ static void machine_set_nvdimm_persistence(Object *obj, const char *value,
     nvdimms_state->persistence_string = g_strdup(value);
 }
 
+static bool machine_get_cxl(Object *obj, Error **errp)
+{
+    MachineState *ms = MACHINE(obj);
+
+    return ms->cxl_devices_state->is_enabled;
+}
+
+static void machine_set_cxl(Object *obj, bool value, Error **errp)
+{
+    MachineState *ms = MACHINE(obj);
+
+    ms->cxl_devices_state->is_enabled = value;
+}
+
 void machine_class_allow_dynamic_sysbus_dev(MachineClass *mc, const char *type)
 {
     QAPI_LIST_PREPEND(mc->allowed_dynamic_sysbus_devices, g_strdup(type));
@@ -911,6 +926,8 @@ static void machine_class_init(ObjectClass *oc, void *data)
     mc->default_ram_size = 128 * MiB;
     mc->rom_file_has_mr = true;
 
+    /* Few machines support CXL, so default to off */
+    mc->cxl_supported = false;
     /* numa node memory size aligned on 8MB by default.
      * On Linux, each node's border has to be 8MB aligned
      */
@@ -1071,6 +1088,16 @@ static void machine_initfn(Object *obj)
                                         "Valid values are cpu, mem-ctrl");
     }
 
+    if (mc->cxl_supported) {
+        Object *obj = OBJECT(ms);
+
+        ms->cxl_devices_state = g_new0(CXLState, 1);
+        object_property_add_bool(obj, "cxl", machine_get_cxl, machine_set_cxl);
+        object_property_set_description(obj, "cxl",
+                                        "Set on/off to enable/disable "
+                                        "CXL instantiation");
+    }
+
     if (mc->cpu_index_to_instance_props && mc->get_default_cpu_node_id) {
         ms->numa_state = g_new0(NumaState, 1);
         object_property_add_bool(obj, "hmat",
@@ -1108,6 +1135,7 @@ static void machine_finalize(Object *obj)
     g_free(ms->device_memory);
     g_free(ms->nvdimms_state);
     g_free(ms->numa_state);
+    g_free(ms->cxl_devices_state);
 }
 
 bool machine_usb(MachineState *machine)

diff --git a/hw/i386/pc.c b/hw/i386/pc.c
index 305d2c082098c5720c53a8a0f6cf1a0ab7630ff6..45e2d6092f5423d9ff233cd0d1873a4e711772b8 100644 (file)
--- a/hw/i386/pc.c
+++ b/hw/i386/pc.c
@@ -1761,6 +1761,7 @@ static void pc_machine_class_init(ObjectClass *oc, void *data)
     mc->default_cpu_type = TARGET_DEFAULT_CPU_TYPE;
     mc->nvdimm_supported = true;
     mc->smp_props.dies_supported = true;
+    mc->cxl_supported = true;
     mc->default_ram_id = "pc.ram";
 
     object_class_property_add(oc, PC_MACHINE_MAX_RAM_BELOW_4G, "size",

diff --git a/include/hw/boards.h b/include/hw/boards.h
index 7b416c97878ca3ff1625b6b6f4cde22f5140b1d3..fa57bac4fb9bd365b30b5b9ff4041da940cccd72 100644 (file)
--- a/include/hw/boards.h
+++ b/include/hw/boards.h
@@ -269,6 +269,7 @@ struct MachineClass {
     bool ignore_boot_device_suffixes;
     bool smbus_no_migration_support;
     bool nvdimm_supported;
+    bool cxl_supported;
     bool numa_mem_supported;
     bool auto_enable_numa;
     SMPCompatProps smp_props;
@@ -359,6 +360,7 @@ struct MachineState {
     CPUArchIdList *possible_cpus;
     CpuTopology smp;
     struct NVDIMMState *nvdimms_state;
+    struct CXLState *cxl_devices_state;
     struct NumaState *numa_state;
 };
 

diff --git a/include/hw/cxl/cxl.h b/include/hw/cxl/cxl.h
index 554ad93b6b9610a5d72a7e5aa885fb2c357adb9e..31af92fd5e13c6561aaa1a382e7066d1dc262aee 100644 (file)
--- a/include/hw/cxl/cxl.h
+++ b/include/hw/cxl/cxl.h
@@ -17,4 +17,8 @@
 #define CXL_COMPONENT_REG_BAR_IDX 0
 #define CXL_DEVICE_REG_BAR_IDX 2
 
+typedef struct CXLState {
+    bool is_enabled;
+} CXLState;
+
 #endif