tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
KVM: arm64: Add support for the KVM PTP service
Implement the hypervisor side of the KVM PTP interface.
The service offers wall time and cycle count from host to guest.
The caller must specify whether they want the host's view of
either the virtual or physical counter.
Signed-off-by: Jianyong Wu <jianyong.wu@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20201209060932.212364-7-jianyong.wu@arm.com
authored by
Jianyong Wu
and committed by
Marc Zyngier
3bf72569
100148d0
+107
+10
Documentation/virt/kvm/api.rst
+10
Documentation/virt/kvm/api.rst
···
6724
6724
The KVM_XEN_HVM_CONFIG_RUNSTATE flag indicates that the runstate-related
6725
6725
features KVM_XEN_VCPU_ATTR_TYPE_RUNSTATE_ADDR/_CURRENT/_DATA/_ADJUST are
6726
6726
supported by the KVM_XEN_VCPU_SET_ATTR/KVM_XEN_VCPU_GET_ATTR ioctls.
6727
+
6728
+
8.31 KVM_CAP_PTP_KVM
6729
+
--------------------
6730
+
6731
+
:Architectures: arm64
6732
+
6733
+
This capability indicates that the KVM virtual PTP service is
6734
+
supported in the host. A VMM can check whether the service is
6735
+
available to the guest on migration.
6736
+
+25
Documentation/virt/kvm/arm/ptp_kvm.rst
+25
Documentation/virt/kvm/arm/ptp_kvm.rst
···
1
+
.. SPDX-License-Identifier: GPL-2.0
2
+
3
+
PTP_KVM support for arm/arm64
4
+
=============================
5
+
6
+
PTP_KVM is used for high precision time sync between host and guests.
7
+
It relies on transferring the wall clock and counter value from the
8
+
host to the guest using a KVM-specific hypercall.
9
+
10
+
* ARM_SMCCC_HYP_KVM_PTP_FUNC_ID: 0x86000001
11
+
12
+
This hypercall uses the SMC32/HVC32 calling convention:
13
+
14
+
ARM_SMCCC_HYP_KVM_PTP_FUNC_ID
15
+
============= ========== ==========
16
+
Function ID: (uint32) 0x86000001
17
+
Arguments: (uint32) KVM_PTP_VIRT_COUNTER(0)
18
+
KVM_PTP_PHYS_COUNTER(1)
19
+
Return Values: (int32) NOT_SUPPORTED(-1) on error, or
20
+
(uint32) Upper 32 bits of wall clock time (r0)
21
+
(uint32) Lower 32 bits of wall clock time (r1)
22
+
(uint32) Upper 32 bits of counter (r2)
23
+
(uint32) Lower 32 bits of counter (r3)
24
+
Endianness: No Restrictions.
25
+
============= ========== ==========
+1
arch/arm64/kvm/arm.c
+1
arch/arm64/kvm/arm.c
+53
arch/arm64/kvm/hypercalls.c
+53
arch/arm64/kvm/hypercalls.c
···
9
9
#include <kvm/arm_hypercalls.h>
10
10
#include <kvm/arm_psci.h>
11
11
12
+
static void kvm_ptp_get_time(struct kvm_vcpu *vcpu, u64 *val)
13
+
{
14
+
struct system_time_snapshot systime_snapshot;
15
+
u64 cycles = ~0UL;
16
+
u32 feature;
17
+
18
+
/*
19
+
* system time and counter value must captured at the same
20
+
* time to keep consistency and precision.
21
+
*/
22
+
ktime_get_snapshot(&systime_snapshot);
23
+
24
+
/*
25
+
* This is only valid if the current clocksource is the
26
+
* architected counter, as this is the only one the guest
27
+
* can see.
28
+
*/
29
+
if (systime_snapshot.cs_id != CSID_ARM_ARCH_COUNTER)
30
+
return;
31
+
32
+
/*
33
+
* The guest selects one of the two reference counters
34
+
* (virtual or physical) with the first argument of the SMCCC
35
+
* call. In case the identifier is not supported, error out.
36
+
*/
37
+
feature = smccc_get_arg1(vcpu);
38
+
switch (feature) {
39
+
case KVM_PTP_VIRT_COUNTER:
40
+
cycles = systime_snapshot.cycles - vcpu_read_sys_reg(vcpu, CNTVOFF_EL2);
41
+
break;
42
+
case KVM_PTP_PHYS_COUNTER:
43
+
cycles = systime_snapshot.cycles;
44
+
break;
45
+
default:
46
+
return;
47
+
}
48
+
49
+
/*
50
+
* This relies on the top bit of val[0] never being set for
51
+
* valid values of system time, because that is *really* far
52
+
* in the future (about 292 years from 1970, and at that stage
53
+
* nobody will give a damn about it).
54
+
*/
55
+
val[0] = upper_32_bits(systime_snapshot.real);
56
+
val[1] = lower_32_bits(systime_snapshot.real);
57
+
val[2] = upper_32_bits(cycles);
58
+
val[3] = lower_32_bits(cycles);
59
+
}
60
+
12
61
int kvm_hvc_call_handler(struct kvm_vcpu *vcpu)
13
62
{
14
63
u32 func_id = smccc_get_function(vcpu);
···
128
79
break;
129
80
case ARM_SMCCC_VENDOR_HYP_KVM_FEATURES_FUNC_ID:
130
81
val[0] = BIT(ARM_SMCCC_KVM_FUNC_FEATURES);
82
+
val[0] |= BIT(ARM_SMCCC_KVM_FUNC_PTP);
83
+
break;
84
+
case ARM_SMCCC_VENDOR_HYP_KVM_PTP_FUNC_ID:
85
+
kvm_ptp_get_time(vcpu, val);
131
86
break;
132
87
case ARM_SMCCC_TRNG_VERSION:
133
88
case ARM_SMCCC_TRNG_FEATURES:
+16
include/linux/arm-smccc.h
+16
include/linux/arm-smccc.h
···
103
103
104
104
/* KVM "vendor specific" services */
105
105
#define ARM_SMCCC_KVM_FUNC_FEATURES 0
106
+
#define ARM_SMCCC_KVM_FUNC_PTP 1
106
107
#define ARM_SMCCC_KVM_FUNC_FEATURES_2 127
107
108
#define ARM_SMCCC_KVM_NUM_FUNCS 128
108
109
···
114
113
ARM_SMCCC_KVM_FUNC_FEATURES)
115
114
116
115
#define SMCCC_ARCH_WORKAROUND_RET_UNAFFECTED 1
116
+
117
+
/*
118
+
* ptp_kvm is a feature used for time sync between vm and host.
119
+
* ptp_kvm module in guest kernel will get service from host using
120
+
* this hypercall ID.
121
+
*/
122
+
#define ARM_SMCCC_VENDOR_HYP_KVM_PTP_FUNC_ID \
123
+
ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL, \
124
+
ARM_SMCCC_SMC_32, \
125
+
ARM_SMCCC_OWNER_VENDOR_HYP, \
126
+
ARM_SMCCC_KVM_FUNC_PTP)
127
+
128
+
/* ptp_kvm counter type ID */
129
+
#define KVM_PTP_VIRT_COUNTER 0
130
+
#define KVM_PTP_PHYS_COUNTER 1
117
131
118
132
/* Paravirtualised time calls (defined by ARM DEN0057A) */
119
133
#define ARM_SMCCC_HV_PV_TIME_FEATURES \