Re: [PATCH v7 07/13] hw/386: Add EPYC mode topology decoding functions

[Eduardo Habkost]

Hi,

It looks like this series breaks -device and CPU hotplug:

On Wed, Mar 11, 2020 at 05:53:34PM -0500, Babu Moger wrote:
> These functions add support for building EPYC mode topology given the smp
> details like numa nodes, cores, threads and sockets.
> 
> The new apic id decoding is mostly similar to current apic id decoding
> except that it adds a new field node_id when numa configured. Removes all
> the hardcoded values. Subsequent patches will use these functions to build
> the topology.
> 
> Following functions are added.
> apicid_llc_width_epyc
> apicid_llc_offset_epyc
> apicid_pkg_offset_epyc
> apicid_from_topo_ids_epyc
> x86_topo_ids_from_idx_epyc
> x86_topo_ids_from_apicid_epyc
> x86_apicid_from_cpu_idx_epyc
> 
> The topology details are available in Processor Programming Reference (PPR)
> for AMD Family 17h Model 01h, Revision B1 Processors. The revision guides are
> available from the bugzilla Link below.
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=206537
> 
> Signed-off-by: Babu Moger <babu.moger@amd.com>
> Acked-by: Igor Mammedov <imammedo@redhat.com>
> Acked-by: Michael S. Tsirkin <mst@redhat.com>
> ---
[...]
>  typedef struct X86CPUTopoIDs {
>      unsigned pkg_id;
> +    unsigned node_id;

You have added a new field here.

>      unsigned die_id;
>      unsigned core_id;
>      unsigned smt_id;
[...]
> +static inline apic_id_t
> +x86_apicid_from_topo_ids_epyc(X86CPUTopoInfo *topo_info,
> +                              const X86CPUTopoIDs *topo_ids)
> +{
> +    return (topo_ids->pkg_id  << apicid_pkg_offset_epyc(topo_info)) |
> +           (topo_ids->node_id << apicid_node_offset_epyc(topo_info)) |

You are using the new field here.

> +           (topo_ids->die_id  << apicid_die_offset(topo_info)) |
> +           (topo_ids->core_id << apicid_core_offset(topo_info)) |
> +           topo_ids->smt_id;
> +}

But you are not initializing node_id in one caller of apicid_from_topo_ids():

static void pc_cpu_pre_plug(HotplugHandler *hotplug_dev,
                            DeviceState *dev, Error **errp)
{
    [...]
    X86CPUTopoIDs topo_ids;
    [...]
    if (cpu->apic_id == UNASSIGNED_APIC_ID) {
        [...]
        topo_ids.pkg_id = cpu->socket_id;
        topo_ids.die_id = cpu->die_id;
        topo_ids.core_id = cpu->core_id;
        topo_ids.smt_id = cpu->thread_id;
        cpu->apic_id = x86ms->apicid_from_topo_ids(&topo_info, &topo_ids);
    }
    [...]
}

Result: -device is broken when using -cpu EPYC:

  $ qemu-system-x86_64 -machine q35,accel=kvm -smp 
1,maxcpus=2,cores=1,threads=1,sockets=2 -cpu EPYC -device 
EPYC-x86_64-cpu,core-id=0,socket-id=1,thread-id=0
  qemu-system-x86_64: -device 
EPYC-x86_64-cpu,core-id=0,socket-id=1,thread-id=0: Invalid CPU [socket: 21855, 
die: 0, core: 0, thread: 0] with APIC ID 21855, valid index range 0:1

This happens because APIC ID is calculated using uninitialized
memory.

-- 
Eduardo