Socket ID is an unsigned value and starts at 0. Subtracting 1 from it is incorrect and the result will underflow if socket_id=0.
Remove substraction when extracting socket_id from c->apicid. Signed-off-by: Yazen Ghannam <yazen.ghan...@amd.com> --- Link: http://lkml.kernel.org/r/1472674900-60688-1-git-send-email-yazen.ghan...@amd.com v1->v2: * Don't do logical AND so as to not restrict # of sockets to 2. arch/x86/kernel/cpu/amd.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c index f3d8a92..793bc23 100644 --- a/arch/x86/kernel/cpu/amd.c +++ b/arch/x86/kernel/cpu/amd.c @@ -365,7 +365,7 @@ static void amd_detect_cmp(struct cpuinfo_x86 *c) if (c->x86 != 0x17 || !cpuid_edx(0x80000006)) return; - socket_id = (c->apicid >> bits) - 1; + socket_id = c->apicid >> bits; core_complex_id = (c->apicid & ((1 << bits) - 1)) >> 3; per_cpu(cpu_llc_id, cpu) = (socket_id << 3) | core_complex_id; -- 1.9.1
