[RFC v2 2/7] hw/core: Define cache topology for machine

Zhao Liu
2024-05-30T10:00:38Z

Define the cache topology based on CPU topology level for two reasons:

1. In practice, a cache will always be bound to the CPU container
(either private in the CPU container or shared among multiple
containers), and CPU container is often expressed in terms of CPU
topology level.
2. The x86's cache-related CPUIDs encode cache topology based on APIC
ID's CPU topology layout. And the ACPI PPTT table that ARM/RISCV
relies on also requires CPU containers to help indicate the private
shared hierarchy of the cache. Therefore, for SMP systems, it is
natural to use the CPU topology hierarchy directly in QEMU to define
the cache topology.

Currently, separated L1 cache (L1 data cache and L1 instruction cache)
with unified higher-level cache (e.g., unified L2 and L3 caches), is the
most common cache architectures.

Therefore, define the topology for L1 D-cache, L1 I-cache, L2 cache and
L3 cache in machine as the basic cache topology support.

Signed-off-by: Zhao Liu <zhao1.liu@intel.com>
---
hw/core/machine.c | 5 +++++
include/hw/boards.h | 25 +++++++++++++++++++++++++
2 files changed, 30 insertions(+)

diff --git a/hw/core/machine.c b/hw/core/machine.c
index 8087026b45da..e31d0f3cb4b0 100644
--- a/hw/core/machine.c
+++ b/hw/core/machine.c
@@ -1175,6 +1175,11 @@ static void machine_initfn(Object *obj)
ms->smp.cores = 1;
ms->smp.threads = 1;

+ ms->smp_cache.l1d = CPU_TOPO_LEVEL_INVALID;
+ ms->smp_cache.l1i = CPU_TOPO_LEVEL_INVALID;
+ ms->smp_cache.l2 = CPU_TOPO_LEVEL_INVALID;
+ ms->smp_cache.l3 = CPU_TOPO_LEVEL_INVALID;
+
machine_copy_boot_config(ms, &(BootConfiguration){ 0 });
}

diff --git a/include/hw/boards.h b/include/hw/boards.h
index c1737f2a5736..e70b2a1bdca2 100644
--- a/include/hw/boards.h
+++ b/include/hw/boards.h
@@ -10,6 +10,7 @@
#include "qemu/module.h"
#include "qom/object.h"
#include "hw/core/cpu.h"
+#include "hw/core/cpu-topology.h"

#define TYPE_MACHINE_SUFFIX "-machine"

@@ -145,6 +146,12 @@ typedef struct {
* @books_supported - whether books are supported by the machine
* @drawers_supported - whether drawers are supported by the machine
* @modules_supported - whether modules are supported by the machine
+ * @l1_separated_cache_supported - whether l1 data and instruction cache
+ * topology are supported by the machine
+ * @l2_unified_cache_supported - whether l2 unified cache topology are
+ * supported by the machine
+ * @l3_unified_cache_supported - whether l3 unified cache topology are
+ * supported by the machine
*/
typedef struct {
bool prefer_sockets;
@@ -154,6 +161,9 @@ typedef struct {
bool books_supported;
bool drawers_supported;
bool modules_supported;
+ bool l1_separated_cache_supported;
+ bool l2_unified_cache_supported;
+ bool l3_unified_cache_supported;
} SMPCompatProps;

/**
@@ -359,6 +369,20 @@ typedef struct CPUTopology {
unsigned int max_cpus;
} CPUTopology;

+/**
+ * CPUTopology:
+ * @l1d: the CPU topology hierarchy the L1 data cache is shared at.
+ * @l1i: the CPU topology hierarchy the L1 instruction cache is shared at.
+ * @l2: the CPU topology hierarchy the L2 (unified) cache is shared at.
+ * @l3: the CPU topology hierarchy the L3 (unified) cache is shared at.
+ */
+typedef struct CacheTopology {
+ CPUTopoLevel l1d;
+ CPUTopoLevel l1i;
+ CPUTopoLevel l2;
+ CPUTopoLevel l3;
+} CacheTopology;
+
/**
* MachineState:
*/
@@ -410,6 +434,7 @@ struct MachineState {
AccelState *accelerator;
CPUArchIdList *possible_cpus;
CPUTopology smp;
+ CacheTopology smp_cache;
struct NVDIMMState *nvdimms_state;
struct NumaState *numa_state;
};
--
2.34.1