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-rw-r--r--Documentation/virtual/kvm/api.txt11
-rw-r--r--arch/x86/kvm/x86.c10
-rw-r--r--include/uapi/linux/kvm.h7
3 files changed, 25 insertions, 3 deletions
diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
index 739db9ab16b2..6bbceb9a3a19 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -777,6 +777,17 @@ Gets the current timestamp of kvmclock as seen by the current guest. In
conjunction with KVM_SET_CLOCK, it is used to ensure monotonicity on scenarios
such as migration.
+When KVM_CAP_ADJUST_CLOCK is passed to KVM_CHECK_EXTENSION, it returns the
+set of bits that KVM can return in struct kvm_clock_data's flag member.
+
+The only flag defined now is KVM_CLOCK_TSC_STABLE. If set, the returned
+value is the exact kvmclock value seen by all VCPUs at the instant
+when KVM_GET_CLOCK was called. If clear, the returned value is simply
+CLOCK_MONOTONIC plus a constant offset; the offset can be modified
+with KVM_SET_CLOCK. KVM will try to make all VCPUs follow this clock,
+but the exact value read by each VCPU could differ, because the host
+TSC is not stable.
+
struct kvm_clock_data {
__u64 clock; /* kvmclock current value */
__u32 flags;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 2f27af4f312a..3320804bb2ac 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2610,7 +2610,6 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
case KVM_CAP_PIT_STATE2:
case KVM_CAP_SET_IDENTITY_MAP_ADDR:
case KVM_CAP_XEN_HVM:
- case KVM_CAP_ADJUST_CLOCK:
case KVM_CAP_VCPU_EVENTS:
case KVM_CAP_HYPERV:
case KVM_CAP_HYPERV_VAPIC:
@@ -2637,6 +2636,9 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
#endif
r = 1;
break;
+ case KVM_CAP_ADJUST_CLOCK:
+ r = KVM_CLOCK_TSC_STABLE;
+ break;
case KVM_CAP_X86_SMM:
/* SMBASE is usually relocated above 1M on modern chipsets,
* and SMM handlers might indeed rely on 4G segment limits,
@@ -4117,9 +4119,11 @@ long kvm_arch_vm_ioctl(struct file *filp,
struct kvm_clock_data user_ns;
u64 now_ns;
- now_ns = get_kvmclock_ns(kvm);
+ local_irq_disable();
+ now_ns = __get_kvmclock_ns(kvm);
user_ns.clock = now_ns;
- user_ns.flags = 0;
+ user_ns.flags = kvm->arch.use_master_clock ? KVM_CLOCK_TSC_STABLE : 0;
+ local_irq_enable();
memset(&user_ns.pad, 0, sizeof(user_ns.pad));
r = -EFAULT;
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 300ef255d1e0..4ee67cb99143 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -972,12 +972,19 @@ struct kvm_irqfd {
__u8 pad[16];
};
+/* For KVM_CAP_ADJUST_CLOCK */
+
+/* Do not use 1, KVM_CHECK_EXTENSION returned it before we had flags. */
+#define KVM_CLOCK_TSC_STABLE 2
+
struct kvm_clock_data {
__u64 clock;
__u32 flags;
__u32 pad[9];
};
+/* For KVM_CAP_SW_TLB */
+
#define KVM_MMU_FSL_BOOKE_NOHV 0
#define KVM_MMU_FSL_BOOKE_HV 1