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Re: [PATCH v2 1/1] xen: update system time immediately when VCPUOP_register_vcpu_info
- To: Dongli Zhang <dongli.zhang@xxxxxxxxxx>, iwj@xxxxxxxxxxxxxx
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Tue, 2 Nov 2021 13:23:00 +0100
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- Cc: sstabellini@xxxxxxxxxx, julien@xxxxxxx, Volodymyr_Babchuk@xxxxxxxx, andrew.cooper3@xxxxxxxxxx, george.dunlap@xxxxxxxxxx, wl@xxxxxxx, joe.jin@xxxxxxxxxx, xen-devel@xxxxxxxxxxxxxxxxxxxx
- Delivery-date: Tue, 02 Nov 2021 12:23:19 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 25.10.2021 19:35, Dongli Zhang wrote:
> The guest may access the pv vcpu_time_info immediately after
> VCPUOP_register_vcpu_info. This is to borrow the idea of
> VCPUOP_register_vcpu_time_memory_area, where the
> force_update_vcpu_system_time() is called immediately when the new memory
> area is registered.
>
> Otherwise, we may observe clock drift at the VM side if the VM accesses
> the clocksource immediately after VCPUOP_register_vcpu_info().
>
> Reference:
> https://lists.xenproject.org/archives/html/xen-devel/2021-10/msg00571.html
> Cc: Joe Jin <joe.jin@xxxxxxxxxx>
> Signed-off-by: Dongli Zhang <dongli.zhang@xxxxxxxxxx>
Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
Ian - any thoughts towards 4.16 here either way?
Jan
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