Re: [PATCH v4 05/10] KVM: arm64: Support stolen time reporting via shared structure

[Zenghui Yu]

On 2019/8/30 16:42, Steven Price wrote:
> Implement the service call for configuring a shared structure between a
> VCPU and the hypervisor in which the hypervisor can write the time
> stolen from the VCPU's execution time by other tasks on the host.
>
> The hypervisor allocates memory which is placed at an IPA chosen by user
> space.

It seems that no allocation happens in the hypervisor code.  User space
will do it instead?

> The hypervisor then updates the shared structure using
> kvm_put_guest() to ensure single copy atomicity of the 64-bit value
> reporting the stolen time in nanoseconds.
>
> Whenever stolen time is enabled by the guest, the stolen time counter is
> reset.
>
> The stolen time itself is retrieved from the sched_info structure
> maintained by the Linux scheduler code. We enable SCHEDSTATS when
> selecting KVM Kconfig to ensure this value is meaningful.
>
> Signed-off-by: Steven Price <steven.price@xxxxxxx>

Thanks,
zenghui