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

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Message-Id: <20211020210348.RFC.v3.3.I6e8f979820f45e38370aa19180a33a8c046d0fa9@changeid>
Date:   Wed, 20 Oct 2021 21:04:28 +0900
From:   Hikaru Nishida <hikalium@...omium.org>
To:     linux-kernel@...r.kernel.org, dme@....org, tglx@...utronix.de,
        mlevitsk@...hat.com, linux@...ck-us.net, pbonzini@...hat.com,
        vkuznets@...hat.com, maz@...nel.org, will@...nel.org
Cc:     suleiman@...gle.com, senozhatsky@...gle.com,
        kvmarm@...ts.cs.columbia.edu, linux-arm-kernel@...ts.infradead.org,
        Hikaru Nishida <hikalium@...omium.org>,
        Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>,
        Jonathan Corbet <corbet@....net>,
        Sean Christopherson <seanjc@...gle.com>,
        Wanpeng Li <wanpengli@...cent.com>, kvm@...r.kernel.org,
        linux-doc@...r.kernel.org, x86@...nel.org
Subject: [RFC PATCH v3 3/5] kvm/x86: virtual suspend time injection: Add common definitions

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@...omium.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