Re: [Qemu-devel] [PATCH v2 07/18] pc: set APIC ID based on socket/core/thread ids if it's not been set yet

[Igor Mammedov]

On Mon, 4 Jul 2016 16:17:09 -0300
Eduardo Habkost <address@hidden> wrote:

> On Fri, Jun 24, 2016 at 06:05:55PM +0200, Igor Mammedov wrote:
> > 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 <address@hidden>
> > ---
> > 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 eaa4b59..0a65caf 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;
> 
> The calculation looks right, but I would love to move this to
> common code that takes care of SMP configuration and topology,
> instead of an inline calculation. We have been bitten by bugs
> related to ad hoc topology calculations before (see commit
> 7dfddd7).
> 
> I think we can do that as a follow-up patch after Drew's series is
> included.
Ok, I can do it on top of Drew's series as follow-up

> > +
> [...]
> > +    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"
> 
> topo.{pkg,core,smt}_id are unsigned. Treating them as signed can
> generate confusing error messages:
> 
>  (qemu) device_add qemu64-x86_64-cpu,apic-id=0xfffffffe
>  Invalid CPU[socket: -2, core: 0, thread: 0] with APIC ID
> (4294967294), valid index range 0:3
> 
> Also, I wonder if showing APIC ID in hex wouldn't be more useful.
it would be easier to read, I'll change it to hex.

> 
> 
> > +                  " 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;
> >      }
> > -- 
> > 1.8.3.1
> > 
> > 
>