[RFC PATCH v3 3/5] kvm/x86: virtual suspend time injection: Add common definitions

Hikaru Nishida
2021-10-20T12:05:26Z

Add definitions of MSR, KVM_FEATURE bit and a structure called
kvm_suspend_time that are used by later patches to support the
virtual suspend time injection mechanism.

Also add documentations for them.

Signed-off-by: Hikaru Nishida <hikalium@chromium.org>
---

Changes in v3:
- Moved the definition of struct kvm_suspend_time into this patch.

Documentation/virt/kvm/cpuid.rst | 3 +++
Documentation/virt/kvm/msr.rst | 30 ++++++++++++++++++++++++++++
arch/x86/include/uapi/asm/kvm_para.h | 6 ++++++
3 files changed, 39 insertions(+)

diff --git a/Documentation/virt/kvm/cpuid.rst b/Documentation/virt/kvm/cpuid.rst
index bda3e3e737d7..f17b95b0d943 100644
--- a/Documentation/virt/kvm/cpuid.rst
+++ b/Documentation/virt/kvm/cpuid.rst
@@ -103,6 +103,9 @@ KVM_FEATURE_HC_MAP_GPA_RANGE 16 guest checks this feature bit bef
KVM_FEATURE_MIGRATION_CONTROL 17 guest checks this feature bit before
using MSR_KVM_MIGRATION_CONTROL

+KVM_FEATURE_HOST_SUSPEND_TIME 18 host suspend time information
+ is available at msr 0x4b564d09.
+
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 9315fc385fb0..40ec0fd263ac 100644
--- a/Documentation/virt/kvm/msr.rst
+++ b/Documentation/virt/kvm/msr.rst
@@ -389,3 +389,33 @@ data:
guest is communicating page encryption status to the host using the
``KVM_HC_MAP_GPA_RANGE`` hypercall, it can set bit 0 in this MSR to
allow live migration of the guest.
+
+MSR_KVM_HOST_SUSPEND_TIME:
+ 0x4b564d09
+
+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_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 visible to the guest (including TSCs) during
+ the host's suspension and report the duration of suspend through this
+ structure. The update will be notified through
+ HYPERVISOR_CALLBACK_VECTOR IRQ. Fields have the following meanings:
+
+ suspend_time_ns:
+ Total number of nanoseconds passed during the host's suspend
+ while the VM is running. This value will be increasing
+ monotonically and cumulative.
+
+ 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 18 in 0x4000001 cpuid
+ leaf prior to usage.
diff --git a/arch/x86/include/uapi/asm/kvm_para.h b/arch/x86/include/uapi/asm/kvm_para.h
index 5146bbab84d4..ccea4e344f46 100644
--- a/arch/x86/include/uapi/asm/kvm_para.h
+++ b/arch/x86/include/uapi/asm/kvm_para.h
@@ -35,6 +35,7 @@
#define KVM_FEATURE_MSI_EXT_DEST_ID 15
#define KVM_FEATURE_HC_MAP_GPA_RANGE 16
#define KVM_FEATURE_MIGRATION_CONTROL 17
+#define KVM_FEATURE_HOST_SUSPEND_TIME 18

#define KVM_HINTS_REALTIME 0

@@ -57,6 +58,7 @@
#define MSR_KVM_ASYNC_PF_INT 0x4b564d06
#define MSR_KVM_ASYNC_PF_ACK 0x4b564d07
#define MSR_KVM_MIGRATION_CONTROL 0x4b564d08
+#define MSR_KVM_HOST_SUSPEND_TIME 0x4b564d09

struct kvm_steal_time {
__u64 steal;
@@ -79,6 +81,10 @@ struct kvm_clock_pairing {
__u32 pad[9];
};

+struct kvm_suspend_time {
+ __u64 suspend_time_ns;
+};
+
#define KVM_STEAL_ALIGNMENT_BITS 5
#define KVM_STEAL_VALID_BITS ((-1ULL << (KVM_STEAL_ALIGNMENT_BITS + 1)))
#define KVM_STEAL_RESERVED_MASK (((1 << KVM_STEAL_ALIGNMENT_BITS) - 1 ) << 1)
--
2.33.0.1079.g6e70778dc9-goog