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@xxxxxxxxxxxx>
---
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:
+ 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
