Re: [Qemu-devel] [PATCH 07/11] pc: set APIC ID based on socket/core/thread ids if it's not been set yet

[Igor Mammedov]

On Thu, 23 Jun 2016 16:27:46 -0300
Eduardo Habkost <address@hidden> wrote:

> On Thu, Jun 23, 2016 at 07:48:24PM +0200, Igor Mammedov wrote:
> > On Thu, 23 Jun 2016 14:19:16 -0300
> > Eduardo Habkost <address@hidden> wrote:
> > 
> > > On Thu, Jun 23, 2016 at 04:54:25PM +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>
> > > > ---
> > > >  hw/i386/pc.c | 18 +++++++++++++-----
> > > >  1 file changed, 13 insertions(+), 5 deletions(-)
> > > > 
> > > > diff --git a/hw/i386/pc.c b/hw/i386/pc.c
> > > > index 87352ae..63e9bb6 100644
> > > > --- a/hw/i386/pc.c
> > > > +++ b/hw/i386/pc.c
> > > > @@ -1758,13 +1758,23 @@ 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(pcms, CPU(dev), &idx);
> > > >  
> > > > +    if (cpu->apic_id == 0xFFFFFFFF) {
> > > > +        /* APIC ID not set, set it based on socket/core/thread
> > > > properties */
> > > > +        X86CPUTopoInfo topo = { cpu->socket, cpu->core,
> > > > cpu->thread };
> > > > +        cpu->apic_id = apicid_from_topo_ids(smp_cores,
> > > > smp_threads, &topo);
> > > > +    }
> > > 
> > > What happens if neither apic-id or socket/core/thread are set?
> > > 
> > > apicid_from_topo_ids() needs the caller to ensure
> > > core_id < nr_cores && smt_id < nr_threads. Do you do that?
> > it will get wrong apic_id and error in "if (!cpu_slot)" will
> > trigger, I can explicitly check for unset values report error
> > saying that they must be set if you prefer.
> 
> Will it? If smp_cores=2 and smp_threads=2,
> socket=0,core=0,thread=3 will generate a valid APIC ID
> (corresponding to socket=0,core=1,thread=1).
> 
> About unset/invalid values: apicid_from_topo_ids() documentation
> explicitly requires core_id < nr_cores && smt_id < nr_threads,
> and may generate a valid APIC ID if only some of the
> socket/core/thread values are set to -1.
> 
> (Also, if you don't check for missing/invalid values explicitly
> you will generate a very confusing error message for the user).
ok, I'll add explicit checks for unset/invalid values here
as you suggested in previous patch.

> 
> > 
> > > 
> > > > +
> > > > +    cpu_slot = pc_find_cpu(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);
> > > 
> > > The error message is a bit confusing: the interface is not based
> > > on CPU index anymore, but it still says "valid index range 0:%d".
> > it's still based on CPU index for cpu-add and -numa cpus,
> > so until we get rid of index in there it still should be printed.
> 
> OK.
> 
> > 
> > > 
> > > >          return;
> > > >      }
> > > > @@ -1780,8 +1790,6 @@ static void pc_cpu_pre_plug(HotplugHandler
> > > > *hotplug_dev,
> > > >       * added CPUs so that query_hotpluggable_cpus would show
> > > > correct values */
> > > >      if (cpu->thread == -1 || cpu->core == -1 || cpu->socket ==
> > > > -1) {
> > > > -        X86CPUTopoInfo topo;
> > > > -
> > > >          x86_topo_ids_from_apicid(cpu->apic_id, smp_cores,
> > > > smp_threads, &topo); cpu->thread = topo.smt_id;
> > > >          cpu->core = topo.core_id;
> > > > -- 
> > > > 1.8.3.1
> > > > 
> > > 
> > 
>