Add a hypercall to retrieve the host realtime clock
and the TSC value used to calculate that clock read.
Used to implement clock synchronization between
host and guest.
Signed-off-by: Marcelo Tosatti <mtosatti@xxxxxxxxxx>
---
Documentation/virtual/kvm/hypercalls.txt | 33 ++++++++++++++++++++++++
arch/x86/include/uapi/asm/kvm_para.h | 9 ++++++
arch/x86/kvm/x86.c | 41 +++++++++++++++++++++++++++++++
include/uapi/linux/kvm_para.h | 3 ++
4 files changed, 86 insertions(+)
v2: improve documentation (Radim)
change hypercall name to KVM_HC_CLOCK_PAIRING (Radim)
increase padding size
Index: kvm-ptpdriver/arch/x86/include/uapi/asm/kvm_para.h
===================================================================
--- kvm-ptpdriver.orig/arch/x86/include/uapi/asm/kvm_para.h 2017-01-13 15:43:47.196867691 -0200
+++ kvm-ptpdriver/arch/x86/include/uapi/asm/kvm_para.h 2017-01-13 15:59:39.596193853 -0200
@@ -50,6 +50,15 @@
__u32 pad[11];
};
+#define KVM_CLOCK_PAIRING_WALLCLOCK 0
+struct kvm_clock_offset {
+ __s64 sec;
+ __s64 nsec;
+ __u64 tsc;
+ __u32 flags;
+ __u32 pad[9];
+};
+
#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)
Index: kvm-ptpdriver/Documentation/virtual/kvm/hypercalls.txt
===================================================================
--- kvm-ptpdriver.orig/Documentation/virtual/kvm/hypercalls.txt 2017-01-13 15:43:47.196867691 -0200
+++ kvm-ptpdriver/Documentation/virtual/kvm/hypercalls.txt 2017-01-13 15:59:26.676163231 -0200
@@ -81,3 +81,36 @@
same guest can wakeup the sleeping vcpu by issuing KVM_HC_KICK_CPU hypercall,
specifying APIC ID (a1) of the vcpu to be woken up. An additional argument (a0)
is used in the hypercall for future use.
+
+
+6. KVM_HC_CLOCK_PAIRING
+------------------------
+Architecture: x86
+Status: active
+Purpose: Hypercall used to synchronize host and guest clocks.
+Usage:
+
+a0: guest physical address where host copies
+"struct kvm_clock_offset" structure.
+
+a1: clock_type, ATM only KVM_CLOCK_PAIRING_WALLCLOCK (0)
+is supported (hosts CLOCK_REALTIME clock).
+
+ struct kvm_clock_offset {
+ __s64 sec;
+ __s64 nsec;
+ __u64 tsc;
+ __u32 flags;
+ __u32 pad[9];
+ };
+
+ Where:
+ * sec: seconds from clock_type clock.
+ * nsec: nanoseconds from clock_type clock.
+ * tsc: TSC value used to calculate sec/nsec pair
+ (this hypercall only works when host uses TSC clocksource).
+ * flags: flags, unused (0) at the moment.
+
+Returns KVM_EOPNOTSUPP if the host does not use TSC clocksource,
+or if clock type is different than KVM_CLOCK_PAIRING_WALLCLOCK.
+
Index: kvm-ptpdriver/arch/x86/kvm/x86.c
===================================================================
--- kvm-ptpdriver.orig/arch/x86/kvm/x86.c 2017-01-13 15:49:14.058347822 -0200
+++ kvm-ptpdriver/arch/x86/kvm/x86.c 2017-01-13 16:00:56.964373208 -0200
@@ -6119,6 +6119,44 @@
}
EXPORT_SYMBOL_GPL(kvm_emulate_halt);
+static int kvm_pv_clock_pairing(struct kvm_vcpu *vcpu, gpa_t paddr,
+ unsigned long clock_type)
+{
+ struct kvm_clock_offset *clock_offset;
+ struct timespec ts;
+ cycle_t cycle;
+ int ret;
+
+ if (clock_type != KVM_CLOCK_PAIRING_WALLCLOCK)
+ return -KVM_EOPNOTSUPP;
+
+ if (pvclock_gtod_data.clock.vclock_mode != VCLOCK_TSC)
+ return -KVM_EOPNOTSUPP;
+
+ clock_offset = kzalloc(sizeof(struct kvm_clock_offset), GFP_KERNEL);
+ if (clock_offset == NULL)
+ return -KVM_ENOMEM;
+
+ if (kvm_get_walltime_and_clockread(&ts, &cycle) == false) {
+ kfree(clock_offset);
+ return -KVM_EOPNOTSUPP;
+ }
+
+ clock_offset->sec = ts.tv_sec;
+ clock_offset->nsec = ts.tv_nsec;
+ clock_offset->tsc = kvm_read_l1_tsc(vcpu, cycle);
+ clock_offset->flags = 0;
+
+ ret = 0;
+ if (kvm_write_guest(vcpu->kvm, paddr, clock_offset,
+ sizeof(struct kvm_clock_offset)))
+ ret = -KVM_EFAULT;
+
+ kfree(clock_offset);
+
+ return ret;
+}
+
/*
* kvm_pv_kick_cpu_op: Kick a vcpu.
*
@@ -6183,6 +6221,9 @@
kvm_pv_kick_cpu_op(vcpu->kvm, a0, a1);
ret = 0;
break;
+ case KVM_HC_CLOCK_PAIRING:
+ ret = kvm_pv_clock_pairing(vcpu, a0, a1);
+ break;
default:
ret = -KVM_ENOSYS;
break;
Index: kvm-ptpdriver/include/uapi/linux/kvm_para.h
===================================================================
--- kvm-ptpdriver.orig/include/uapi/linux/kvm_para.h 2017-01-13 15:43:47.196867691 -0200
+++ kvm-ptpdriver/include/uapi/linux/kvm_para.h 2017-01-13 16:01:09.290401187 -0200
@@ -14,6 +14,8 @@
#define KVM_EFAULT EFAULT
#define KVM_E2BIG E2BIG
#define KVM_EPERM EPERM
+#define KVM_EOPNOTSUPP EOPNOTSUPP
+#define KVM_ENOMEM ENOMEM
#define KVM_HC_VAPIC_POLL_IRQ 1
#define KVM_HC_MMU_OP 2
@@ -23,6 +25,7 @@
#define KVM_HC_MIPS_GET_CLOCK_FREQ 6
#define KVM_HC_MIPS_EXIT_VM 7
#define KVM_HC_MIPS_CONSOLE_OUTPUT 8
+#define KVM_HC_CLOCK_PAIRING 9
/*
* hypercalls use architecture specific
--
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