Re: [Qemu-devel] [PATCH v3 07/19] pc: set APIC ID based on socket/core/thread ids if it's not been set yet

[Bandan Das <bsd@redhat.com>]

Eduardo Habkost <ehabkost@redhat.com> writes:

> On Wed, Jul 13, 2016 at 06:24:17PM -0400, Bandan Das wrote:
>> Igor Mammedov <imammedo@redhat.com> writes:
>> 
>> > CPU added with device_add help won't have APIC ID set,
>> > so set it according to socket/core/thread ids provided
>> > with device_add command.
>> >
>> > Signed-off-by: Igor Mammedov <imammedo@redhat.com>
>> > ---
>> > v3:
>> >  - use %u for printing topo ids
>> > v2:
>> >  - add validity checks for socket-id/core-id/thread-id values
>> > ---
>> >  hw/i386/pc.c | 44 +++++++++++++++++++++++++++++++++++++++++---
>> >  1 file changed, 41 insertions(+), 3 deletions(-)
>> >
>> > diff --git a/hw/i386/pc.c b/hw/i386/pc.c
>> > index 24231ca..29da2d4 100644
>> > --- a/hw/i386/pc.c
>> > +++ b/hw/i386/pc.c
>> > @@ -1763,14 +1763,52 @@ static void pc_cpu_pre_plug(HotplugHandler *hotplug_dev,
>> >                              DeviceState *dev, Error **errp)
>> >  {
>> >      int idx;
>> > +    CPUArchId *cpu_slot;
>> >      X86CPUTopoInfo topo;
>> >      X86CPU *cpu = X86_CPU(dev);
>> >      PCMachineState *pcms = PC_MACHINE(hotplug_dev);
>> > -    CPUArchId *cpu_slot = pc_find_cpu_slot(pcms, CPU(dev), &idx);
>> >  
>> > +    /* if APIC ID is not set, set it based on socket/core/thread properties */
>> > +    if (cpu->apic_id == UNASSIGNED_APIC_ID) {
>> > +        int max_socket = (max_cpus - 1) / smp_threads / smp_cores;
>> > +
>> > +        if (cpu->socket_id < 0) {
>> > +            error_setg(errp, "CPU socket-id is not set");
>> > +            return;
>> > +        } else if (cpu->socket_id > max_socket) {
>> > +            error_setg(errp, "Invalid CPU socket-id: %u must be in range 0:%u",
>> > +                       cpu->socket_id, max_socket);
>> > +            return;
>> > +        }
>> > +        if (cpu->core_id < 0) {
>> > +            error_setg(errp, "CPU core-id is not set");
>> > +            return;
>> > +        } else if (cpu->core_id > (smp_cores - 1)) {
>> > +            error_setg(errp, "Invalid CPU core-id: %u must be in range 0:%u",
>> > +                       cpu->core_id, smp_cores - 1);
>> > +            return;
>> > +        }
>> > +        if (cpu->thread_id < 0) {
>> > +            error_setg(errp, "CPU thread-id is not set");
>> > +            return;
>> > +        } else if (cpu->thread_id > (smp_threads - 1)) {
>> > +            error_setg(errp, "Invalid CPU thread-id: %u must be in range 0:%u",
>> > +                       cpu->thread_id, smp_threads - 1);
>> > +            return;
>> > +        }
>> 
>> Just curoious, when any of these values < 0, the only other values that they
>> can take is -1, right ?
>
> No, the user might have set thread=-2 explicitly, and this is
> where we validate the user-provided values.
>
>> I am wondering why decided to do the check differently
>> for in the preceeding patch.
>
> Because on both cases we want thread_id <= -2 to generate an
> error message. On patch 06/19, thread_id == -1 is one case where
> the error message will be skipped (but thread_id == -2 will
> generate an error). In this patch, all negative values should
> generate an error.

Understood, this makes sense. Thanks.

>> 
>> Bandan
>> > +        topo.pkg_id = cpu->socket_id;
>> > +        topo.core_id = cpu->core_id;
>> > +        topo.smt_id = cpu->thread_id;
>> > +        cpu->apic_id = apicid_from_topo_ids(smp_cores, smp_threads, &topo);
>> > +    }
>> > +
>> > +    cpu_slot = pc_find_cpu_slot(pcms, CPU(dev), &idx);
>> >      if (!cpu_slot) {
>> > -        error_setg(errp, "Invalid CPU index with APIC ID (%" PRIu32
>> > -                   "), valid range 0:%d", cpu->apic_id,
>> > +        x86_topo_ids_from_apicid(cpu->apic_id, smp_cores, smp_threads, &topo);
>> > +        error_setg(errp, "Invalid CPU[socket: %d, core: %d, thread: %d] with"
>> > +                  " APIC ID (%" PRIu32 "), valid index range 0:%d",
>> > +                   topo.pkg_id, topo.core_id, topo.smt_id, cpu->apic_id,
>> >                     pcms->possible_cpus->len - 1);
>> >          return;
>> >      }