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SubjectRe: [RFC PATCH 1/6] x86/kvm: Reserve KVM_FEATURE_HOST_SUSPEND_TIME and MSR_KVM_HOST_SUSPEND_TIME
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On Monday, 2021-04-26 at 18:06:40 +09, Hikaru Nishida wrote:

> No functional change; just add documentation for
> KVM_FEATURE_HOST_SUSPEND_TIME and its corresponding
> MSR_KVM_HOST_SUSPEND_TIME to support virtual suspend timing injection in
> later patches.
>
> Signed-off-by: Hikaru Nishida <hikalium@chromium.org>
> ---
>
> Documentation/virt/kvm/cpuid.rst | 3 +++
> Documentation/virt/kvm/msr.rst | 29 +++++++++++++++++++++++++++++
> 2 files changed, 32 insertions(+)
>
> diff --git a/Documentation/virt/kvm/cpuid.rst b/Documentation/virt/kvm/cpuid.rst
> index cf62162d4be2..c7cb581b9a9b 100644
> --- a/Documentation/virt/kvm/cpuid.rst
> +++ b/Documentation/virt/kvm/cpuid.rst
> @@ -96,6 +96,9 @@ KVM_FEATURE_MSI_EXT_DEST_ID 15 guest checks this feature bit
> before using extended destination
> ID bits in MSI address bits 11-5.
>
> +KVM_FEATURE_HOST_SUSPEND_TIME 16 host suspend time information
> + is available at msr 0x4b564d08.
> +
> KVM_FEATURE_CLOCKSOURCE_STABLE_BIT 24 host will warn if no guest-side
> per-cpu warps are expected in
> kvmclock
> diff --git a/Documentation/virt/kvm/msr.rst b/Documentation/virt/kvm/msr.rst
> index e37a14c323d2..de96743245c9 100644
> --- a/Documentation/virt/kvm/msr.rst
> +++ b/Documentation/virt/kvm/msr.rst
> @@ -376,3 +376,32 @@ data:
> write '1' to bit 0 of the MSR, this causes the host to re-scan its queue
> and check if there are more notifications pending. The MSR is available
> if KVM_FEATURE_ASYNC_PF_INT is present in CPUID.
> +
> +MSR_KVM_HOST_SUSPEND_TIME:
> + 0x4b564d08
> +
> +data:
> + 8-byte alignment physical address of a memory area which must be
> + in guest RAM, plus an enable bit in bit 0. This memory is expected to
> + hold a copy of the following structure::
> +
> + struct kvm_host_suspend_time {
> + __u64 suspend_time_ns;
> + };
> +
> + whose data will be filled in by the hypervisor.
> + If the guest register this structure through the MSR write, the host
> + will stop all the clocks including TSCs observed by the guest during
> + the host's suspension and report the duration of suspend through this
> + structure. Fields have the following meanings:
> +
> + host_suspend_time_ns:

s/host_suspend_time_ns/suspend_time_ns/

> + Total number of nanoseconds passed during the host's suspend
> + while the VM is running. This value will be increasing
> + monotonically.
> +
> + Note that although MSRs are per-CPU entities, the effect of this
> + particular MSR is global.
> +
> + Availability of this MSR must be checked via bit 16 in 0x4000001 cpuid
> + leaf prior to usage.
> --
> 2.31.1.498.g6c1eba8ee3d-goog

dme.
--
I do believe it's Madame Joy.

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