x86: cpu: make sure number of addressable IDs for processor cores meets the spec

Accourding Intel's CPUID[EAX=04H] resulting bits 31 - 26 in EAX
should be:
"
 **** The nearest power-of-2 integer that is not smaller than (1 + EAX[31:26]) is the number of unique
    Core_IDs reserved for addressing different processor cores in a physical package. Core ID is a subset of
    bits of the initial APIC ID.
"

ensure that values stored in EAX[31-26] always meets this condition.

Signed-off-by: Igor Mammedov <[email protected]>
Message-Id: <[email protected]>
Signed-off-by: Paolo Bonzini <[email protected]>

Author: Igor Mammedov

target/i386/cpu.c

@@ -5287,7 +5287,7 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t index, uint32_t count,
             /* QEMU gives out its own APIC IDs, never pass down bits 31..26.  */
             *eax &= ~0xFC000000;
             if ((*eax & 31) && cs->nr_cores > 1) {
-                *eax |= (cs->nr_cores - 1) << 26;
+                *eax |= (pow2ceil(cs->nr_cores) - 1) << 26;
             }
         } else if (cpu->vendor_cpuid_only && IS_AMD_CPU(env)) {
             *eax = *ebx = *ecx = *edx = 0;