Re: [PATCH v5 0/8] Remove EPYC mode apicid decode and use generic decode

[Dr. David Alan Gilbert]

* Babu Moger (babu.moger@amd.com) wrote:
> To support some of the complex topology, we introduced EPYC mode apicid 
> decode.
> But, EPYC mode decode is running into problems. Also it can become quite a
> maintenance problem in the future. So, it was decided to remove that code and
> use the generic decode which works for majority of the topology. Most of the
> SPECed configuration would work just fine. With some non-SPECed user inputs,
> it will create some sub-optimal configuration.
> Here is the discussion thread.
> c0bcc1a6-1d84-a6e7-e468-d5b437c1b254@amd.com/">https://lore.kernel.org/qemu-devel/c0bcc1a6-1d84-a6e7-e468-d5b437c1b254@amd.com/
> 
> This series removes all the EPYC mode specific apicid changes and use the 
> generic
> apicid decode.

Hi Babu,
  This does simplify things a lot!
One worry, what happens about a live migration of a VM from an old qemu
that was using the node-id to a qemu with this new scheme?

Dave

> ---
> v5:
>  Revert EPYC specific decode.
>  Simplify CPUID_8000_001E
> 
> v4:
>   
> 159744083536.39197.13827776633866601278.stgit@naples-babu.amd.com/">https://lore.kernel.org/qemu-devel/159744083536.39197.13827776633866601278.stgit@naples-babu.amd.com/
>   Not much of a change. Just added few text changes.
>   Error out configuration instead of warning if dies are not configured in 
> EPYC.
>   Few other text changes to clarify the removal of node_id, nr_nodes and 
> nodes_per_pkg.
> 
> v3:
>   
> 159681772267.9679.1334429994189974662.stgit@naples-babu.amd.com/#r">https://lore.kernel.org/qemu-devel/159681772267.9679.1334429994189974662.stgit@naples-babu.amd.com/#r
>   Added a new check to pass the dies for EPYC numa configuration.
>   Added Simplify CPUID_8000_001E patch with some changes suggested by Igor.
>   Dropped the patch to build the topology from CpuInstanceProperties.
>   TODO: Not sure if we still need the Autonuma changes Igor mentioned.
>   Needs more clarity on that.
> 
> v2:
>   
> https://lore.kernel.org/qemu-devel/159362436285.36204.986406297373871949.stgit@naples-babu.amd.com/
>   Used the numa information from CpuInstanceProperties for building
>   the apic_id suggested by Igor.
>   Also did some minor code re-aarangement to take care of changes.
>   Dropped the patch "Simplify CPUID_8000_001E" from v1. Will send
>   it later.
> 
> v1:
>  
> https://lore.kernel.org/qemu-devel/159164739269.20543.3074052993891532749.stgit@naples-babu.amd.com
> 
> Babu Moger (8):
>       hw/i386: Remove node_id, nr_nodes and nodes_per_pkg from topology
>       Revert "i386: Fix pkg_id offset for EPYC cpu models"
>       Revert "target/i386: Enable new apic id encoding for EPYC based cpus 
> models"
>       Revert "hw/i386: Move arch_id decode inside x86_cpus_init"
>       Revert "i386: Introduce use_epyc_apic_id_encoding in X86CPUDefinition"
>       Revert "hw/i386: Introduce apicid functions inside X86MachineState"
>       Revert "hw/386: Add EPYC mode topology decoding functions"
>       i386: Simplify CPUID_8000_001E for AMD
> 
> 
>  hw/i386/pc.c               |    8 +--
>  hw/i386/x86.c              |   43 +++-------------
>  include/hw/i386/topology.h |  101 ---------------------------------------
>  include/hw/i386/x86.h      |    9 ---
>  target/i386/cpu.c          |  115 
> ++++++++++++++++----------------------------
>  target/i386/cpu.h          |    3 -
>  tests/test-x86-cpuid.c     |   40 ++++++++-------
>  7 files changed, 73 insertions(+), 246 deletions(-)
> 
> --
> Signature
> 
-- 
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK