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Re: [BUG] Migration hv_time rollback
From: |
Dr. David Alan Gilbert |
Subject: |
Re: [BUG] Migration hv_time rollback |
Date: |
Wed, 16 Sep 2020 12:29:56 +0100 |
User-agent: |
Mutt/1.14.6 (2020-07-11) |
cc'ing in Vitaly who knows about the hv stuff.
* Antoine Damhet (antoine.damhet@blade-group.com) wrote:
> Hi,
>
> We are experiencing timestamp rollbacks during live-migration of
> Windows 10 guests with the following qemu configuration (linux 5.4.46
> and qemu master):
> ```
> $ qemu-system-x86_64 -enable-kvm -cpu host,kvm=off,hv_time [...]
> ```
How big a jump are you seeing, and how did you notice it in the guest?
Dave
> I have tracked the bug to the fact that `kvmclock` is not exposed and
> disabled from qemu PoV but is in fact used by `hv-time` (in KVM).
>
> I think we should enable the `kvmclock` (qemu device) if `hv-time` is
> present and add Hyper-V support for the `kvmclock_current_nsec`
> function.
>
> I'm asking for advice because I am unsure this is the _right_ approach
> and how to keep migration compatibility between qemu versions.
>
> Thank you all,
>
> --
> Antoine 'xdbob' Damhet
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK