[pve-devel] [PATCH v8 0/8] Add basics for custom CPU models

[Stefan Reiter]

Hi,

On 2/13/20 1:27 PM, Eneko Lacunza wrote:
> Hi Stefan,
> 
> Do you think this could help specifying a custom CPU model that will 
> migrate VMs with more than 1 core between Intel and AMD CPUs?
> https://bugzilla.proxmox.com/show_bug.cgi?id=1660
> 

as discussed on the bug report you linked, live migration between hosts 
using different vendors' CPUs is very much unsupported in general (with 
KVM-enabled VMs). Even if it _appears_ to work, there are no guarantees 
about stability.

That said, if you find a specific CPU flag configuration that seems to 
work for you (like comment #12 in the report mentions), this series 
would indeed allow you to specify it as a custom CPU model instead of 
having to use the '-args' parameter.

Hope that helps,

Stefan

> Thanks a lot
> Eneko
> 
> 
> El 12/2/20 a las 16:11, Stefan Reiter escribió:
>> Based on the RFC and following on- and off-list discussion about 
>> custom CPU
>> models [0].
>>
>> In essence, this revised patch allows a user to specify custom CPU 
>> models in
>> /etc/pve/cpu-models.conf (section-config style [1]), where VMs using 
>> that CPU
>> model inherit details from the definition. This removes any fragile
>> "auto-magical" CPU flag detection, while still giving the user a way 
>> to create
>> VMs with the best possible subset of CPU features maintaining 
>> live-migration
>> compatibility.
>>
>> Includes the infrastructure for broadcasting supported CPU flags for each
>> cluster-node via the key-value store - this is not necessary for the
>> custom-cpu feature in particular, but I think could prove useful for
>> implementing the GUI part (e.g. show the user which flags are 
>> supported on which
>> nodes).
>>
>>
>> v7 -> v8:
>> * rebase on master, fix tests now using +pve0
>> * fixed nits noted by Thomas
>> * moved live-migration/snapshot patches forward to avoid temporary 
>> breakage
>> * fix CPU hotplug with custom CPUs
>> * guard mkdir with check_cfs_is_mounted and also run before write
>> * fix rebase-error in cfg2cmd tests (getaddrinfo_all)
>> * dropped applied patches
>>
>> I deliberately didn't add any version_guard checks, since I don't 
>> think a bump
>> is the right thing to do here (I say, after I waited for the 
>> pve-version series
>> to be applied for making this v8).
>>
>> Doing so would break custom CPUs on older machine versions (since I'd 
>> have to
>> pin it to 4.1~pve2) for no reason. The idea would have been to show a 
>> neat error
>> message, but since up to this point we didn't even check the 
>> pve-version on
>> migration, it wouldn't help much. Besides, migration to older versions 
>> already
>> fails cleanly with a semi-readable message ('Unknown option: force-cpu').
>>
>>
>> < see [2] for older history >
>>
>>
>> [0]: https://pve.proxmox.com/pipermail/pve-devel/2019-July/038268.html
>> [1]: e.g.:
>> cpu-model: custom-cpu-name
>>      host-phys-bits 1
>>      flags +aes;+avx;+avx2
>>      reported-model kvm64
>> [2] https://pve.proxmox.com/pipermail/pve-devel/2020-January/041278.html
>>
>>
>> qemu-server: Stefan Reiter (8):
>>    Adapt CPUConfig to handle custom models
>>    Verify VM-specific CPU configs seperately
>>    Include "-cpu" parameter with live-migration
>>    Include "-cpu" parameter with snapshots/suspend
>>    Add helpers to better structure CPU option handling
>>    Rework get_cpu_options and allow custom CPU models
>>    fix #2318: allow phys-bits and host-phys-bits CPU settings
>>    cfg2cmd: add test cases for custom CPU models
>>
>>   PVE/API2/Qemu.pm                              |  10 +-
>>   PVE/QemuConfig.pm                             |  36 +-
>>   PVE/QemuMigrate.pm                            |  22 +
>>   PVE/QemuServer.pm                             |  44 +-
>>   PVE/QemuServer/CPUConfig.pm                   | 477 +++++++++++++++---
>>   test/cfg2cmd/custom-cpu-model-defaults.conf   |   8 +
>>   .../custom-cpu-model-defaults.conf.cmd        |  24 +
>>   test/cfg2cmd/custom-cpu-model.conf            |   8 +
>>   test/cfg2cmd/custom-cpu-model.conf.cmd        |  27 +
>>   test/cfg2cmd/i440fx-win10-hostpci.conf.cmd    |   2 +-
>>   test/cfg2cmd/minimal-defaults.conf.cmd        |   2 +-
>>   test/cfg2cmd/pinned-version.conf.cmd          |   2 +-
>>   .../q35-linux-hostpci-multifunction.conf.cmd  |   2 +-
>>   test/cfg2cmd/q35-linux-hostpci.conf.cmd       |   2 +-
>>   test/cfg2cmd/q35-win10-hostpci.conf.cmd       |   2 +-
>>   test/cfg2cmd/simple1.conf.cmd                 |   2 +-
>>   test/cfg2cmd/spice-enhancments.conf.cmd       |   2 +-
>>   test/cfg2cmd/spice-linux-4.1.conf.cmd         |   2 +-
>>   test/cfg2cmd/spice-usb3.conf.cmd              |   2 +-
>>   test/cfg2cmd/spice-win.conf.cmd               |   2 +-
>>   test/run_config2command_tests.pl              |  23 +
>>   21 files changed, 609 insertions(+), 92 deletions(-)
>>   create mode 100644 test/cfg2cmd/custom-cpu-model-defaults.conf
>>   create mode 100644 test/cfg2cmd/custom-cpu-model-defaults.conf.cmd
>>   create mode 100644 test/cfg2cmd/custom-cpu-model.conf
>>   create mode 100644 test/cfg2cmd/custom-cpu-model.conf.cmd
>>
> 
>