i386/cpu: Honor maximum value for CPUID.8000001DH.EAX[25:14]

CPUID.8000001DH:EAX[25:14] is "NumSharingCache", and the number of
logical processors sharing this cache is the value of this field
incremented by 1. Because of its width limitation, the maximum value
currently supported is 4095.

Though at present Q35 supports up to 4096 CPUs, by constructing a
specific topology, the width of the APIC ID can be extended beyond 12
bits. For example, using `-smp threads=33,cores=9,modules=9` results in
a die level offset of 6 + 4 + 4 = 14 bits, which can also cause
overflow. Check and honor the maximum value as CPUID.04H did.

Cc: Babu Moger <[email protected]>
Signed-off-by: Zhao Liu <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Paolo Bonzini <[email protected]>
(cherry picked from commit 5d21ee453ad8e3f95f75e542cb3b35c5bb7cf23a)
Signed-off-by: Michael Tokarev <[email protected]>

Author: trueptolemy

target/i386/cpu.c

@@ -496,7 +496,8 @@ static void encode_cache_cpuid8000001d(CPUCacheInfo *cache,
 
     *eax = CACHE_TYPE(cache->type) | CACHE_LEVEL(cache->level) |
                (cache->self_init ? CACHE_SELF_INIT_LEVEL : 0);
-    *eax |= max_thread_ids_for_cache(topo_info, cache->share_level) << 14;
+    /* Bits 25:14 - NumSharingCache: maximum 4095. */
+    *eax |= MIN(max_thread_ids_for_cache(topo_info, cache->share_level), 4095) << 14;
 
     assert(cache->line_size > 0);
     assert(cache->partitions > 0);