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

On 2019/8/30 16:42, Steven Price wrote:

quoted

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

quoted

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@arm.com>

Thanks,
zenghui

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