Re: [Qemu-devel] [PATCH for-1.4 00/12] target-i386: Fix APIC-ID-based topology (v4)

[li guang <lig.fnst@cn.fujitsu.com>]

在 2013-01-18五的 12:49 -0200，Eduardo Habkost写道：
> On Fri, Jan 18, 2013 at 02:54:41PM +0800, li guang wrote:
> > 在 2013-01-17四的 18:59 -0200，Eduardo Habkost写道：
> > > I am hoping to get this bug fixed in 1.4. I didn't get much feedback on the RFC
> > > I sent last week, though.
> > > 
> > > Igor argued that APIC ID should be set by the board and not by the CPU itself,
> > 
> > per Intel's SPEC, seems APIC ID really based on design of board.
> > (refer to Intel® 64 and IA-32 Architectures
> >     Software Developer’s Manual
> >                 Volume 3 (3A, 3B & 3C):
> >              System Programming Guide
> >      chapter 10.4.6)
> > but, actually, it maybe meaningless for emulation.
> > after go though your patches,
> > I can't capture the purpose you do a topology map between 
> > APIC ID and cpu_index, (sorry for that)
> > can you help to clear that?
> 
> See the documents mentioned on PATCH 11/12:
> 
> +/* This file implements the APIC-ID-based CPU topology enumeration logic,
> + * documented at the following document:
> + *   Intel® 64 Architecture Processor Topology Enumeration
> + *   http://software.intel.com/en-us/articles/intel-64-architecture-processor-topology-enumeration/
> + *
> + * This code should be compatible with AMD's "Extended Method" described at:
> + *   AMD CPUID Specification (Publication #25481)
> + *   Section 3: Multiple Core Calcuation
> + * as long as:
> + *  nr_threads is set to 1;
> + *  OFFSET_IDX is assumed to be 0;
> + *  CPUID Fn8000_0008_ECX[ApicIdCoreIdSize[3:0]] is set to apicid_core_width().
> + */
> 
> If we don't generate the APIC IDs properly, identification of CPU
> sockets/cores/threads is broken.
> 
> e.g. today -smp 12,cores=3,threads=2 currently ends up exposing 4 cores on the
> first socket, and 2 cores in the second one, because the APIC IDs are generated
> sequentially instead of being based on package/core/thread IDs.

okay, Thanks!

> 
> > 
> > > but I am not doing that because:
> > >  - I want to keep the bug fix simple and isolated as we are past soft freeze
> > >  - I believe the creator of the CPU object shouldn't be forced to provide the
> > >    APIC ID, so the APIC ID is not unnecessarily exposed on the CPU hotplug
> > >    device_add interface in the future
> > >  - The APIC ID _is_ set by the CPU itself (because each CPU package may have
> > >    multiple core/threads, and each core/thread has a different APIC ID). What
> > >    needs to be provided by the board to the CPU package in the future is the
> > >    package ID and the bit width of the core/thread IDs.
> > > 
> > > Git tree for reference:
> > >   git://github.com/ehabkost/qemu-hacks.git apicid-topology.v5
> > >   https://github.com/ehabkost/qemu-hacks/tree/apicid-topology.v5
> > > 
> > > Eduardo Habkost (12):
> > >   kvm: Add fake KVM_FEATURE_CLOCKSOURCE_STABLE_BIT for builds withou
> > >     KVM
> > >   target-i386: Don't set any KVM flag by default if KVM is disabled
> > >   pc: Reverse pc_init_pci() compatibility logic
> > >   kvm: Create kvm_arch_vcpu_id() function
> > >   target-i386: kvm: Set vcpu_id to APIC ID instead of CPU index
> > >   fw_cfg: Remove FW_CFG_MAX_CPUS from fw_cfg_init()
> > >   target-i386/cpu: Introduce apic_id_for_cpu() function
> > >   cpus.h: Make constant smp_cores/smp_threads available on *-user
> > >   pc: Set fw_cfg data based on APIC ID calculation
> > >   tests: Support target-specific unit tests
> > >   target-i386: Topology & APIC ID utility functions
> > >   pc: Generate APIC IDs according to CPU topology
> > > 
> > >  hw/fw_cfg.c            |   1 -
> > >  hw/pc.c                |  44 +++++++++++++---
> > >  hw/pc_piix.c           |  26 +++++++---
> > >  hw/ppc_newworld.c      |   1 +
> > >  hw/ppc_oldworld.c      |   1 +
> > >  hw/sun4m.c             |   3 ++
> > >  hw/sun4u.c             |   1 +
> > >  include/sysemu/cpus.h  |   7 +++
> > >  include/sysemu/kvm.h   |   4 ++
> > >  kvm-all.c              |   2 +-
> > >  target-i386/cpu.c      |  52 +++++++++++++++----
> > >  target-i386/cpu.h      |   5 +-
> > >  target-i386/kvm.c      |   6 +++
> > >  target-i386/topology.h | 133 +++++++++++++++++++++++++++++++++++++++++++++++++
> > >  target-ppc/kvm.c       |   5 ++
> > >  target-s390x/kvm.c     |   5 ++
> > >  tests/.gitignore       |   1 +
> > >  tests/Makefile         |  21 +++++++-
> > >  tests/test-x86-cpuid.c | 101 +++++++++++++++++++++++++++++++++++++
> > >  19 files changed, 391 insertions(+), 28 deletions(-)
> > >  create mode 100644 target-i386/topology.h
> > >  create mode 100644 tests/test-x86-cpuid.c
> > > 
> > 
> > -- 
> > regards!
> > li guang
> > 
> > 
> 

-- 
regards!
li guang