Re: Kernel patch cases qemu live migration failed.

[Marc Zyngier]

Hi

Please don't use my arm.com address anymore, nobody reads it...

On 2020-10-15 05:06, 张东旭 wrote:
> I'm so sorry for disturbing you.
>
> When I apply this kernel patch：KVM: arm64/sve: System register
> context switch and access support
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/arch/arm64/kvm/sys_regs.c?id=73433762fcaeb9d59e84d299021c6b15466c96dd

This patch was only introduced in 5.2, and wasn't supposed to be
backported to anything else.

> qemu live migration will failed with messages：
>               ​qemu-kvm: Invalid value 233 expecting positive value
> <= 232
>               qemu-kvm: Failed to load cpu:cpreg_vmstate_array_len
> New version kernel  exclude ID_AA64ZFR0_EL1 register when host not
> support SVE feature,
> so qemu ioctl kvm(KVM_GET_REG_LIST) will not contain ID_AA64ZFR0_EL1
> register.
>
> I'm using CentOS Linux kernel, old kernel version：4.18.0-80.11.el8
> (migration source)
>       new kernel version：4.18.0-147.5.el8 (migration destination)
>
> CentOS linux kernel version 4.18.0-111.el8 applied this patch. So
> 4.18.0-147.5.el8 also applied this patch.
>
> Migration source and destination hosts have the same hardware, just
> kernel version is different,
> and the hardware on either side of the migration not support SVE.
>
> Is there some good suggestions，which can make sure old version
> kernel live migration to new version kernel with qemu?

I['m afraid you should take this with your distribution of
choice, unless you can reproduce the problem with mainline kernels.

Thanks,

        M.
--
Jazz is not dead. It just smells funny...