On Thu, Feb 20, 2025 at 12:23:26PM +0530, Ani Sinha wrote:
> Date: Thu, 20 Feb 2025 12:23:26 +0530
> From: Ani Sinha <anisi...@redhat.com>
> Subject: [PATCH v2] microvm: do not use the lastest cpu version
> X-Mailer: git-send-email 2.45.2
>
> commit 0788a56bd1ae3 ("i386: Make unversioned CPU models be aliases")
> introduced 'default_cpu_version' for PCMachineClass. This created three
> categories of CPU models:
> - Most unversioned CPU models would use version 1 by default.
> - For machines 4.0.1 and older that do not support cpu model aliases, a
> special default_cpu_version value of CPU_VERSION_LEGACY is used.
> - It was thought that future machines would use the latest value of cpu
> versions corresponding to default_cpu_version value of
> CPU_VERSION_LATEST [1].
>
> All pc machines still use the default cpu version of 1 for
> unversioned cpu models. CPU_VERSION_LATEST is a moving target and
> changes with time. Therefore, if machines use CPU_VERSION_LATEST, it would
> mean that over a period of time, for the same versioned machine type,
> the cpu version would be different depending on what the latest was at that
> time. This would break guests even when they use a constant specific
> versioned machine type.
> Additionally, microvm machines are not versioned anyway and therefore
> there is no requirement to use the latest cpu model by default.
> Let microvms use the non-versioned cpu model and remove all references
> to CPU_VERSION_LATEST as there are no other users (nor we anticipate
> future consumers of CPU_VERSION_LATEST).
>
> Those users who need spefific cpu versions can use explicit version in
> the QEMU command line to select the specific cpu version desired.
>
> CI pipline does not break with this change.
>
> 1) See commit dcafd1ef0af227 ("i386: Register versioned CPU models")
>
> CC: imamm...@redhat.com
> CC: zhao1....@intel.com
> Reviewed-by: Igor Mammedov <imamm...@redhat.com>
> Reviewed-by: Sergio Lopez <s...@redhat.com>
> Signed-off-by: Ani Sinha <anisi...@redhat.com>
> ---
> hw/i386/microvm.c | 2 +-
> target/i386/cpu.c | 15 ---------------
> target/i386/cpu.h | 4 ----
> 3 files changed, 1 insertion(+), 20 deletions(-)
>
> changelog:
> v2: tags added, more explanation in the commit log.
Reviewed-by: Zhao Liu <zhao1....@intel.com>
