CPUID leaf CPUID_Fn80000008_ECX provides information about the number of threads supported by the processor. It was found that the field ApicIdSize(bits 15-12) was not set correctly.
ApicIdSize is defined as the number of bits required to represent all the ApicId values within a package. Valid Values: Value Description 3h-0h Reserved. 4h up to 16 threads. 5h up to 32 threads. 6h up to 64 threads. 7h up to 128 threads. Fh-8h Reserved. Fix the bit appropriately. This came up during following thread. https://lore.kernel.org/qemu-devel/158643709116.17430.15995069125716778943.malone...@wampee.canonical.com/#t Refer the Processor Programming Reference (PPR) for AMD Family 17h Model 01h, Revision B1 Processors. The documentation is available from the bugzilla Link below. Link: https://bugzilla.kernel.org/show_bug.cgi?id=206537 Reported-by: Philipp Eppelt <1871...@bugs.launchpad.net> Signed-off-by: Babu Moger <babu.mo...@amd.com> --- target/i386/cpu.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) diff --git a/target/i386/cpu.c b/target/i386/cpu.c index 90ffc5f..68210f6 100644 --- a/target/i386/cpu.c +++ b/target/i386/cpu.c @@ -5830,11 +5830,17 @@ void cpu_x86_cpuid(CPUX86State *env, uint32_t index, uint32_t count, *eax = cpu->phys_bits; } *ebx = env->features[FEAT_8000_0008_EBX]; - *ecx = 0; - *edx = 0; if (cs->nr_cores * cs->nr_threads > 1) { - *ecx |= (cs->nr_cores * cs->nr_threads) - 1; + unsigned int max_apicids, bits_required; + + max_apicids = (cs->nr_cores * cs->nr_threads) - 1; + /* Find out the number of bits to represent all the apicids */ + bits_required = 32 - clz32(max_apicids); + *ecx = bits_required << 12 | max_apicids; + } else { + *ecx = 0; } + *edx = 0; break; case 0x8000000A: if (env->features[FEAT_8000_0001_ECX] & CPUID_EXT3_SVM) {
