[PATCH v8 3/3] KVM: x86: Add "suspendsteal" cmdline to request host to add suspend duration in steal time

[Suleiman Souhlal <suleiman@google.com>]

Introduce a new command line parameter, "suspendsteal", enabling the
guest to use MSR_KVM_SUSPEND_STEAL, which tells the host that it would
like host suspend duration to be included in steal time.

Signed-off-by: Suleiman Souhlal <suleiman@google.com>
---
 Documentation/admin-guide/kernel-parameters.txt |  5 +++++
 arch/x86/kernel/kvm.c                           | 15 +++++++++++++++
 2 files changed, 20 insertions(+)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 07e22ba5bfe3..9a5490539bb2 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -7074,6 +7074,11 @@
 			improve throughput, but will also increase the
 			amount of memory reserved for use by the client.
 
+	suspendsteal
+			[X86,PV_OPS]
+			Enable requesting the host to include the duration the
+			host was suspended in steal time. Disabled by default.
+
 	suspend.pm_test_delay=
 			[SUSPEND]
 			Sets the number of seconds to remain in a suspend test
diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
index 921c1c783bc1..35d1bb2283c2 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -320,6 +320,18 @@ static void __init paravirt_ops_setup(void)
 #endif
 }
 
+static bool suspend_steal;
+
+static int __init suspendsteal_setup(char *s)
+{
+	if (kvm_para_has_feature(KVM_FEATURE_SUSPEND_STEAL))
+		suspend_steal = true;
+
+	return 0;
+}
+
+early_param("suspendsteal", suspendsteal_setup);
+
 static void kvm_register_steal_time(void)
 {
 	int cpu = smp_processor_id();
@@ -331,6 +343,9 @@ static void kvm_register_steal_time(void)
 	wrmsrq(MSR_KVM_STEAL_TIME, (slow_virt_to_phys(st) | KVM_MSR_ENABLED));
 	pr_debug("stealtime: cpu %d, msr %llx\n", cpu,
 		(unsigned long long) slow_virt_to_phys(st));
+
+	if (suspend_steal)
+		wrmsrl(MSR_KVM_SUSPEND_STEAL, KVM_MSR_ENABLED);
 }
 
 static DEFINE_PER_CPU_DECRYPTED(unsigned long, kvm_apic_eoi) = KVM_PV_EOI_DISABLED;
-- 
2.50.0.727.gbf7dc18ff4-goog