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

[Steven Price]

On 03/09/2019 10:14, Zenghui Yu wrote:
> 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?

Ah, yes I should update the commit message. User space does now allocate
the memory. Thanks for spotting that.

Steve

>> 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
>