[PATCH v4 5/9] hw/core: Add a helper to check the cache topology level

[Zhao Liu <zhao1.liu@xxxxxxxxx>]

Currently, we have no way to expose the arch-specific default cache
model because the cache model is sometimes related to the CPU model
(e.g., i386).

Since the user might configure "default" level, any comparison with
"default" is meaningless before the machine knows the specific level
that "default" refers to.

We can only check the correctness of the cache topology after the arch
loads the user-configured cache model from MachineState.smp_cache and
consumes the special "default" level by replacing it with the specific
level.

Signed-off-by: Zhao Liu <zhao1.liu@xxxxxxxxx>
---
Changes since Patch v3:
 * New commit to make cache topology check as a separate helper, so that
   arch-specific code could use this helper to check cache topology.
---
 hw/core/machine-smp.c | 48 +++++++++++++++++++++++++++++++++++++++++++
 include/hw/boards.h   |  1 +
 2 files changed, 49 insertions(+)

diff --git a/hw/core/machine-smp.c b/hw/core/machine-smp.c
index ebb7a134a7be..640b2114b429 100644
--- a/hw/core/machine-smp.c
+++ b/hw/core/machine-smp.c
@@ -348,3 +348,51 @@ void machine_set_cache_topo_level(MachineState *ms, CacheLevelAndType cache,
 {
     ms->smp_cache.props[cache].topology = level;
 }
+
+/*
+ * When both cache1 and cache2 are configured with specific topology levels
+ * (not default level), is cache1's topology level higher than cache2?
+ */
+static bool smp_cache_topo_cmp(const SmpCache *smp_cache,
+                               CacheLevelAndType cache1,
+                               CacheLevelAndType cache2)
+{
+    /*
+     * Before comparing, the "default" topology level should be replaced
+     * with the specific level.
+     */
+    assert(smp_cache->props[cache1].topology != CPU_TOPOLOGY_LEVEL_DEFAULT);
+
+    return smp_cache->props[cache1].topology > smp_cache->props[cache2].topology;
+}
+
+/*
+ * Currently, we have no way to expose the arch-specific default cache model
+ * because the cache model is sometimes related to the CPU model (e.g., i386).
+ *
+ * We can only check the correctness of the cache topology after the arch loads
+ * the user-configured cache model from MachineState and consumes the special
+ * "default" level by replacing it with the specific level.
+ */
+bool machine_check_smp_cache(const MachineState *ms, Error **errp)
+{
+    if (smp_cache_topo_cmp(&ms->smp_cache, CACHE_LEVEL_AND_TYPE_L1D,
+                           CACHE_LEVEL_AND_TYPE_L2) ||
+        smp_cache_topo_cmp(&ms->smp_cache, CACHE_LEVEL_AND_TYPE_L1I,
+                           CACHE_LEVEL_AND_TYPE_L2)) {
+        error_setg(errp,
+                   "Invalid smp cache topology. "
+                   "L2 cache topology level shouldn't be lower than L1 cache");
+        return false;
+    }
+
+    if (smp_cache_topo_cmp(&ms->smp_cache, CACHE_LEVEL_AND_TYPE_L2,
+                           CACHE_LEVEL_AND_TYPE_L3)) {
+        error_setg(errp,
+                   "Invalid smp cache topology. "
+                   "L3 cache topology level shouldn't be lower than L2 cache");
+        return false;
+    }
+
+    return true;
+}
diff --git a/include/hw/boards.h b/include/hw/boards.h
index 3d6cb5acd6c7..192f78539a6e 100644
--- a/include/hw/boards.h
+++ b/include/hw/boards.h
@@ -53,6 +53,7 @@ CpuTopologyLevel machine_get_cache_topo_level(const MachineState *ms,
                                               CacheLevelAndType cache);
 void machine_set_cache_topo_level(MachineState *ms, CacheLevelAndType cache,
                                   CpuTopologyLevel level);
+bool machine_check_smp_cache(const MachineState *ms, Error **errp);
 void machine_memory_devices_init(MachineState *ms, hwaddr base, uint64_t size);
 
 /**
-- 
2.34.1