i386/cpu: Allow cache to be shared at thread level

In CPUID 0x4 leaf, it's possible to make the cache privated at thread
level when there's no HT within the core. In this case, while cache per
thread and cache per core are essentially identical, their topology
information differs in CPUID 0x4.

Diamond Rapids assigns the L1 i/d cache at the thread level. To allow
accurate emulation of DMR cache topology, remove the cache-per-thread
restriction in max_thread_ids_for_cache(), which enables CPUID 0x4 to
support cache per thread topology.

Given that after adding thread-level support, the topology offset
information required by max_thread_ids_for_cache() can be sufficiently
provided by apicid_offset_by_topo_level(), so it's straightforward to
re-implement max_thread_ids_for_cache() based on
apicid_offset_by_topo_level() to reduce redundant duplicate codes.

Tested-by: Xudong Hao <xudong.hao@intel.com>
Signed-off-by: Zhao Liu <zhao1.liu@intel.com>
Link: https://lore.kernel.org/r/20251215073743.4055227-8-zhao1.liu@intel.com
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/target/i386/cpu.c b/target/i386/cpu.c
index f62bd48d4b0b679496f45a88d86509461a9539dd..4ed7f4f1c9965fae4f3c1b803847621fb71fe47c 100644 (file)
--- a/target/i386/cpu.c
+++ b/target/i386/cpu.c
@@ -304,33 +304,30 @@ static void encode_cache_cpuid2(X86CPU *cpu,
                        ((t) == UNIFIED_CACHE) ? CACHE_TYPE_UNIFIED : \
                        0 /* Invalid value */)
 
-static uint32_t max_thread_ids_for_cache(X86CPUTopoInfo *topo_info,
-                                         enum CpuTopologyLevel share_level)
+static uint32_t apicid_offset_by_topo_level(X86CPUTopoInfo *topo_info,
+                                            enum CpuTopologyLevel topo_level)
 {
-    uint32_t num_ids = 0;
-
-    switch (share_level) {
+    switch (topo_level) {
+    case CPU_TOPOLOGY_LEVEL_THREAD:
+        return 0;
     case CPU_TOPOLOGY_LEVEL_CORE:
-        num_ids = 1 << apicid_core_offset(topo_info);
-        break;
+        return apicid_core_offset(topo_info);
     case CPU_TOPOLOGY_LEVEL_MODULE:
-        num_ids = 1 << apicid_module_offset(topo_info);
-        break;
+        return apicid_module_offset(topo_info);
     case CPU_TOPOLOGY_LEVEL_DIE:
-        num_ids = 1 << apicid_die_offset(topo_info);
-        break;
+        return apicid_die_offset(topo_info);
     case CPU_TOPOLOGY_LEVEL_SOCKET:
-        num_ids = 1 << apicid_pkg_offset(topo_info);
-        break;
+        return apicid_pkg_offset(topo_info);
     default:
-        /*
-         * Currently there is no use case for THREAD, so use
-         * assert directly to facilitate debugging.
-         */
         g_assert_not_reached();
     }
+    return 0;
+}
 
-    return num_ids - 1;
+static uint32_t max_thread_ids_for_cache(X86CPUTopoInfo *topo_info,
+                                         enum CpuTopologyLevel share_level)
+{
+    return (1 << apicid_offset_by_topo_level(topo_info, share_level)) - 1;
 }
 
 static uint32_t max_core_ids_in_package(X86CPUTopoInfo *topo_info)
@@ -398,26 +395,6 @@ static uint32_t num_threads_by_topo_level(X86CPUTopoInfo *topo_info,
     return 0;
 }
 
-static uint32_t apicid_offset_by_topo_level(X86CPUTopoInfo *topo_info,
-                                            enum CpuTopologyLevel topo_level)
-{
-    switch (topo_level) {
-    case CPU_TOPOLOGY_LEVEL_THREAD:
-        return 0;
-    case CPU_TOPOLOGY_LEVEL_CORE:
-        return apicid_core_offset(topo_info);
-    case CPU_TOPOLOGY_LEVEL_MODULE:
-        return apicid_module_offset(topo_info);
-    case CPU_TOPOLOGY_LEVEL_DIE:
-        return apicid_die_offset(topo_info);
-    case CPU_TOPOLOGY_LEVEL_SOCKET:
-        return apicid_pkg_offset(topo_info);
-    default:
-        g_assert_not_reached();
-    }
-    return 0;
-}
-
 static uint32_t cpuid1f_topo_type(enum CpuTopologyLevel topo_level)
 {
     switch (topo_level) {