RE: [Qemu-devel] [RFC PATCH 0/6] hw/arm/virt: Introduce cpu topology support

["Zengtao (B)" <prime.zeng@hisilicon.com>]

Hi Andrew:

Any update for this patch series? I have met the same issue, and if the 
topology guessed by linux MPIDR conflicts with qemu specified numa, it
will failed to boot (sched domain initialization will fall into deadloop).

Thanks.

> -----Original Message-----
> From: Qemu-devel
> [mailto:qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.or
> g] On Behalf Of Andrew Jones
> Sent: Thursday, July 05, 2018 4:49 AM
> To: qemu-devel@nongnu.org; qemu-arm@nongnu.org
> Cc: wei@redhat.com; peter.maydell@linaro.org; eric.auger@redhat.com;
> imammedo@redhat.com
> Subject: [Qemu-devel] [RFC PATCH 0/6] hw/arm/virt: Introduce cpu
> topology support
> 
> This series provides support for booting mach-virt machines with
> non-flat cpu topology, i.e. enabling the extended options of the
> '-smp' command line parameter (sockets,cores,threads). Both DT and
> ACPI description generators are added. We only apply the new feature
> to 3.1 and later machine types, as the change is guest visible, even
> when no command line change is made. This is because the basic
> '-smp <N>' parameter makes the assumption that <N> refers to the
> number of sockets, but when no topology description is provided,
> Linux will use the MPIDR to guess. Neither the MPIDR exposed to
> the guest when running with KVM nor TCG currently provides socket
> information, leaving Linux to assume all processing elements are
> cores in the same socket. For example, before this series '-smp 4'
> would show up in the guest as
> 
>  CPU(s):                4
>  On-line CPU(s) list:   0-3
>  Thread(s) per core:    1
>  Core(s) per socket:    4
>  Socket(s):             1
> 
> and after it shows up as
> 
>  CPU(s):                4
>  On-line CPU(s) list:   0-3
>  Thread(s) per core:    1
>  Core(s) per socket:    1
>  Socket(s):             4
> 
> It's not expected that this should be a problem, but it's worth
> considering. The only way to avoid the silent change is for QEMU to
> provide boards a way to override the default '-smp' parsing function.
> Otherwise, if a user wants to avoid a guest visible change, but still
> use a 3.1 or later mach-virt machine type, then they must ensure the
> command line specifies a single socket, e.g. '-smp sockets=1,cores=4'
> 
> Thanks,
> drew
> 
> 
> Andrew Jones (6):
>   hw/arm/virt: Add virt-3.1 machine type
>   device_tree: add qemu_fdt_add_path
>   hw/arm/virt: DT: add cpu-map
>   hw/arm/virt-acpi-build: distinguish possible and present cpus
>   virt-acpi-build: add PPTT table
>   hw/arm/virt: cpu topology: don't allow threads
> 
>  device_tree.c                | 24 +++++++++++++
>  hw/acpi/aml-build.c          | 50 ++++++++++++++++++++++++++
>  hw/arm/virt-acpi-build.c     | 25 ++++++++++---
>  hw/arm/virt.c                | 69
> +++++++++++++++++++++++++++++++++---
>  include/hw/acpi/aml-build.h  |  2 ++
>  include/hw/arm/virt.h        |  1 +
>  include/sysemu/device_tree.h |  1 +
>  7 files changed, 162 insertions(+), 10 deletions(-)