Re: [PATCH RFCv2 00/20] kvm/arm: Introduce a customizable aarch64 KVM host model

[Sebastian Ott]

On Fri, 6 Dec 2024, Cornelia Huck wrote:
> A respin/update on the aarch64 KVM cpu models. Also available at
> gitlab.com/cohuck/qemu arm-cpu-model-rfcv2
>
> Find Eric's original cover letter below, so that I do not need to
> repeat myself on the aspects that have not changed since RFCv1 :)
>
> Changes from RFCv1:
>
> Rebased on more recent QEMU (some adaptions in the register conversions
> of the first few patches.)
>
> Based on feedback, I have removed the "custom" cpu model; instead, I
> have added the new SYSREG_<REG>_<FIELD> properties to the "host" model.
> This works well if you want to tweak anything that does not correspond
> to the existing properties for the host model; however, if you e.g.
> wanted to tweak sve, you have two ways to do so -- we'd probably either
> want to check for conflicts, or just declare precedence. The kvm-specific
> props remain unchanged, as they are orthogonal to this configuration.
>
> The cpu model expansion for the "host" model now dumps the new SYSREG_
> properties in addition to the existing host model properties; this is a
> bit ugly, but I don't see a good way on how to split this up.

I gave this a spin today and successfully migrated a VM between 2 similar
machines that only differ in the DIC bit of the cache type register using:

        -cpu host,SYSREG_CTR_EL0_DIC=0

This allows me to get rid of my horrid qemu hacks to achieve the same.

Thanks,
Sebastian