Currently, there is no mechanism to keep time sync between guest and host
in arm/arm64 virtualization environment. Time in guest will drift compared
with host after boot up as they may both use third party time sources
to correct their time respectively. The time deviation will be in order
of milliseconds. But in some scenarios,like in cloud envirenment, we ask
for higher time precision.
kvm ptp clock, which chooses the host clock source as a reference
clock to sync time between guest and host, has been adopted by x86
which takes the time sync order from milliseconds to nanoseconds.
This patch enables kvm ptp clock for arm/arm64 and improves clock sync precison
significantly.
Test result comparisons between with kvm ptp clock and without it in arm/arm64
are as follows. This test derived from the result of command 'chronyc
sources'. we should take more care of the last sample column which shows
the offset between the local clock and the source at the last measurement.
no kvm ptp in guest:
MS Name/IP address Stratum Poll Reach LastRx Last sample
========================================================================
^* dns1.synet.edu.cn 2 6 377 13 +1040us[+1581us] +/- 21ms
^* dns1.synet.edu.cn 2 6 377 21 +1040us[+1581us] +/- 21ms
^* dns1.synet.edu.cn 2 6 377 29 +1040us[+1581us] +/- 21ms
^* dns1.synet.edu.cn 2 6 377 37 +1040us[+1581us] +/- 21ms
^* dns1.synet.edu.cn 2 6 377 45 +1040us[+1581us] +/- 21ms
^* dns1.synet.edu.cn 2 6 377 53 +1040us[+1581us] +/- 21ms
^* dns1.synet.edu.cn 2 6 377 61 +1040us[+1581us] +/- 21ms
^* dns1.synet.edu.cn 2 6 377 4 -130us[ +796us] +/- 21ms
^* dns1.synet.edu.cn 2 6 377 12 -130us[ +796us] +/- 21ms
^* dns1.synet.edu.cn 2 6 377 20 -130us[ +796us] +/- 21ms
in host:
MS Name/IP address Stratum Poll Reach LastRx Last sample
========================================================================
^* 120.25.115.20 2 7 377 72 -470us[ -603us] +/- 18ms
^* 120.25.115.20 2 7 377 92 -470us[ -603us] +/- 18ms
^* 120.25.115.20 2 7 377 112 -470us[ -603us] +/- 18ms
^* 120.25.115.20 2 7 377 2 +872ns[-6808ns] +/- 17ms
^* 120.25.115.20 2 7 377 22 +872ns[-6808ns] +/- 17ms
^* 120.25.115.20 2 7 377 43 +872ns[-6808ns] +/- 17ms
^* 120.25.115.20 2 7 377 63 +872ns[-6808ns] +/- 17ms
^* 120.25.115.20 2 7 377 83 +872ns[-6808ns] +/- 17ms
^* 120.25.115.20 2 7 377 103 +872ns[-6808ns] +/- 17ms
^* 120.25.115.20 2 7 377 123 +872ns[-6808ns] +/- 17ms
The dns1.synet.edu.cn is the network reference clock for guest and
120.25.115.20 is the network reference clock for host. we can't get the
clock error between guest and host directly, but a roughly estimated value
will be in order of hundreds of us to ms.
with kvm ptp in guest:
chrony has been disabled in host to remove the disturb by network clock.
MS Name/IP address Stratum Poll Reach LastRx Last sample
========================================================================
* PHC0 0 3 377 8 -7ns[ +1ns] +/- 3ns
* PHC0 0 3 377 8 +1ns[ +16ns] +/- 3ns
* PHC0 0 3 377 6 -4ns[ -0ns] +/- 6ns
* PHC0 0 3 377 6 -8ns[ -12ns] +/- 5ns
* PHC0 0 3 377 5 +2ns[ +4ns] +/- 4ns
* PHC0 0 3 377 13 +2ns[ +4ns] +/- 4ns
* PHC0 0 3 377 12 -4ns[ -6ns] +/- 4ns
* PHC0 0 3 377 11 -8ns[ -11ns] +/- 6ns
* PHC0 0 3 377 10 -14ns[ -20ns] +/- 4ns
* PHC0 0 3 377 8 +4ns[ +5ns] +/- 4ns
The PHC0 is the ptp clock which choose the host clock as its source
clock. So we can see that the clock difference between host and guest
is in order of ns.
Signed-off-by: Jianyong Wu <[email protected]>
---
drivers/clocksource/arm_arch_timer.c | 28 ++++++++++++++++++
drivers/ptp/Kconfig | 2 +-
drivers/ptp/Makefile | 1 +
drivers/ptp/ptp_kvm_arm.c | 44 ++++++++++++++++++++++++++++
4 files changed, 74 insertions(+), 1 deletion(-)
create mode 100644 drivers/ptp/ptp_kvm_arm.c
diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c
index d55acffb0b90..b33c5a663d30 100644
--- a/drivers/clocksource/arm_arch_timer.c
+++ b/drivers/clocksource/arm_arch_timer.c
@@ -25,6 +25,7 @@
#include <linux/sched/clock.h>
#include <linux/sched_clock.h>
#include <linux/acpi.h>
+#include <linux/arm-smccc.h>
#include <asm/arch_timer.h>
#include <asm/virt.h>
@@ -1650,3 +1651,30 @@ static int __init arch_timer_acpi_init(struct acpi_table_header *table)
}
TIMER_ACPI_DECLARE(arch_timer, ACPI_SIG_GTDT, arch_timer_acpi_init);
#endif
+
+int kvm_arch_ptp_get_crosststamp(u64 *cycle, struct timespec64 *ts,
+ struct clocksource **cs)
+{
+ struct arm_smccc_res hvc_res;
+ ktime_t ktime;
+ u32 ptp_counter;
+
+ if (arch_timer_uses_ppi == ARCH_TIMER_VIRT_PPI)
+ ptp_counter = ARM_PTP_VIRT_COUNTER;
+ else
+ ptp_counter = ARM_PTP_PHY_COUNTER;
+
+ arm_smccc_1_1_invoke(ARM_SMCCC_VENDOR_HYP_KVM_PTP_FUNC_ID,
+ ptp_counter, &hvc_res);
+
+ if ((int)(hvc_res.a0) < 0)
+ return -EOPNOTSUPP;
+
+ ktime = (u64)hvc_res.a0 << 32 | hvc_res.a1;
+ *ts = ktime_to_timespec64(ktime);
+ *cycle = (u64)hvc_res.a2 << 32 | hvc_res.a3;
+ *cs = &clocksource_counter;
+
+ return 0;
+}
+EXPORT_SYMBOL_GPL(kvm_arch_ptp_get_crosststamp);
diff --git a/drivers/ptp/Kconfig b/drivers/ptp/Kconfig
index 942f72d8151d..677c7f696b70 100644
--- a/drivers/ptp/Kconfig
+++ b/drivers/ptp/Kconfig
@@ -106,7 +106,7 @@ config PTP_1588_CLOCK_PCH
config PTP_1588_CLOCK_KVM
tristate "KVM virtual PTP clock"
depends on PTP_1588_CLOCK
- depends on KVM_GUEST && X86
+ depends on KVM_GUEST && X86 || (HAVE_ARM_SMCCC_DISCOVERY && ARM_ARCH_TIMER)
default y
help
This driver adds support for using kvm infrastructure as a PTP
diff --git a/drivers/ptp/Makefile b/drivers/ptp/Makefile
index 699a4e4d19c2..9fa5ede44b2b 100644
--- a/drivers/ptp/Makefile
+++ b/drivers/ptp/Makefile
@@ -5,6 +5,7 @@
ptp-y := ptp_clock.o ptp_chardev.o ptp_sysfs.o
ptp_kvm-$(CONFIG_X86) := ptp_kvm_x86.o ptp_kvm_common.o
+ptp_kvm-$(CONFIG_HAVE_ARM_SMCCC) := ptp_kvm_arm.o ptp_kvm_common.o
obj-$(CONFIG_PTP_1588_CLOCK) += ptp.o
obj-$(CONFIG_PTP_1588_CLOCK_DTE) += ptp_dte.o
obj-$(CONFIG_PTP_1588_CLOCK_INES) += ptp_ines.o
diff --git a/drivers/ptp/ptp_kvm_arm.c b/drivers/ptp/ptp_kvm_arm.c
new file mode 100644
index 000000000000..2212827c0384
--- /dev/null
+++ b/drivers/ptp/ptp_kvm_arm.c
@@ -0,0 +1,44 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Virtual PTP 1588 clock for use with KVM guests
+ * Copyright (C) 2019 ARM Ltd.
+ * All Rights Reserved
+ */
+
+#include <linux/kernel.h>
+#include <linux/err.h>
+#include <asm/hypervisor.h>
+#include <linux/module.h>
+#include <linux/psci.h>
+#include <linux/arm-smccc.h>
+#include <linux/timecounter.h>
+#include <linux/sched/clock.h>
+#include <asm/arch_timer.h>
+#include <asm/hypervisor.h>
+
+int kvm_arch_ptp_init(void)
+{
+ int ret;
+
+ ret = kvm_arm_hyp_service_available(ARM_SMCCC_KVM_FUNC_KVM_PTP);
+ if (ret <= 0)
+ return -EOPNOTSUPP;
+
+ return 0;
+}
+
+int kvm_arch_ptp_get_clock(struct timespec64 *ts)
+{
+ ktime_t ktime;
+ struct arm_smccc_res hvc_res;
+
+ arm_smccc_1_1_invoke(ARM_SMCCC_VENDOR_HYP_KVM_PTP_FUNC_ID,
+ ARM_PTP_NONE_COUNTER, &hvc_res);
+ if ((int)(hvc_res.a0) < 0)
+ return -EOPNOTSUPP;
+
+ ktime = (u64)hvc_res.a0 << 32 | hvc_res.a1;
+ *ts = ktime_to_timespec64(ktime);
+
+ return 0;
+}
--
2.17.1
On 2020-11-11 06:22, Jianyong Wu wrote:
> Currently, there is no mechanism to keep time sync between guest and
> host
> in arm/arm64 virtualization environment. Time in guest will drift
> compared
> with host after boot up as they may both use third party time sources
> to correct their time respectively. The time deviation will be in order
> of milliseconds. But in some scenarios,like in cloud envirenment, we
> ask
environment
> for higher time precision.
>
> kvm ptp clock, which chooses the host clock source as a reference
> clock to sync time between guest and host, has been adopted by x86
> which takes the time sync order from milliseconds to nanoseconds.
>
> This patch enables kvm ptp clock for arm/arm64 and improves clock sync
> precison
precision
> significantly.
>
> Test result comparisons between with kvm ptp clock and without it in
> arm/arm64
> are as follows. This test derived from the result of command 'chronyc
> sources'. we should take more care of the last sample column which
> shows
> the offset between the local clock and the source at the last
> measurement.
>
> no kvm ptp in guest:
> MS Name/IP address Stratum Poll Reach LastRx Last sample
> ========================================================================
> ^* dns1.synet.edu.cn 2 6 377 13 +1040us[+1581us] +/-
> 21ms
> ^* dns1.synet.edu.cn 2 6 377 21 +1040us[+1581us] +/-
> 21ms
> ^* dns1.synet.edu.cn 2 6 377 29 +1040us[+1581us] +/-
> 21ms
> ^* dns1.synet.edu.cn 2 6 377 37 +1040us[+1581us] +/-
> 21ms
> ^* dns1.synet.edu.cn 2 6 377 45 +1040us[+1581us] +/-
> 21ms
> ^* dns1.synet.edu.cn 2 6 377 53 +1040us[+1581us] +/-
> 21ms
> ^* dns1.synet.edu.cn 2 6 377 61 +1040us[+1581us] +/-
> 21ms
> ^* dns1.synet.edu.cn 2 6 377 4 -130us[ +796us] +/-
> 21ms
> ^* dns1.synet.edu.cn 2 6 377 12 -130us[ +796us] +/-
> 21ms
> ^* dns1.synet.edu.cn 2 6 377 20 -130us[ +796us] +/-
> 21ms
>
> in host:
> MS Name/IP address Stratum Poll Reach LastRx Last sample
> ========================================================================
> ^* 120.25.115.20 2 7 377 72 -470us[ -603us] +/-
> 18ms
> ^* 120.25.115.20 2 7 377 92 -470us[ -603us] +/-
> 18ms
> ^* 120.25.115.20 2 7 377 112 -470us[ -603us] +/-
> 18ms
> ^* 120.25.115.20 2 7 377 2 +872ns[-6808ns] +/-
> 17ms
> ^* 120.25.115.20 2 7 377 22 +872ns[-6808ns] +/-
> 17ms
> ^* 120.25.115.20 2 7 377 43 +872ns[-6808ns] +/-
> 17ms
> ^* 120.25.115.20 2 7 377 63 +872ns[-6808ns] +/-
> 17ms
> ^* 120.25.115.20 2 7 377 83 +872ns[-6808ns] +/-
> 17ms
> ^* 120.25.115.20 2 7 377 103 +872ns[-6808ns] +/-
> 17ms
> ^* 120.25.115.20 2 7 377 123 +872ns[-6808ns] +/-
> 17ms
>
> The dns1.synet.edu.cn is the network reference clock for guest and
> 120.25.115.20 is the network reference clock for host. we can't get the
> clock error between guest and host directly, but a roughly estimated
> value
> will be in order of hundreds of us to ms.
>
> with kvm ptp in guest:
> chrony has been disabled in host to remove the disturb by network
> clock.
>
> MS Name/IP address Stratum Poll Reach LastRx Last sample
> ========================================================================
> * PHC0 0 3 377 8 -7ns[ +1ns] +/-
> 3ns
> * PHC0 0 3 377 8 +1ns[ +16ns] +/-
> 3ns
> * PHC0 0 3 377 6 -4ns[ -0ns] +/-
> 6ns
> * PHC0 0 3 377 6 -8ns[ -12ns] +/-
> 5ns
> * PHC0 0 3 377 5 +2ns[ +4ns] +/-
> 4ns
> * PHC0 0 3 377 13 +2ns[ +4ns] +/-
> 4ns
> * PHC0 0 3 377 12 -4ns[ -6ns] +/-
> 4ns
> * PHC0 0 3 377 11 -8ns[ -11ns] +/-
> 6ns
> * PHC0 0 3 377 10 -14ns[ -20ns] +/-
> 4ns
> * PHC0 0 3 377 8 +4ns[ +5ns] +/-
> 4ns
>
> The PHC0 is the ptp clock which choose the host clock as its source
> clock. So we can see that the clock difference between host and guest
> is in order of ns.
>
> Signed-off-by: Jianyong Wu <[email protected]>
> ---
> drivers/clocksource/arm_arch_timer.c | 28 ++++++++++++++++++
> drivers/ptp/Kconfig | 2 +-
> drivers/ptp/Makefile | 1 +
> drivers/ptp/ptp_kvm_arm.c | 44 ++++++++++++++++++++++++++++
> 4 files changed, 74 insertions(+), 1 deletion(-)
> create mode 100644 drivers/ptp/ptp_kvm_arm.c
>
> diff --git a/drivers/clocksource/arm_arch_timer.c
> b/drivers/clocksource/arm_arch_timer.c
> index d55acffb0b90..b33c5a663d30 100644
> --- a/drivers/clocksource/arm_arch_timer.c
> +++ b/drivers/clocksource/arm_arch_timer.c
> @@ -25,6 +25,7 @@
> #include <linux/sched/clock.h>
> #include <linux/sched_clock.h>
> #include <linux/acpi.h>
> +#include <linux/arm-smccc.h>
>
> #include <asm/arch_timer.h>
> #include <asm/virt.h>
> @@ -1650,3 +1651,30 @@ static int __init arch_timer_acpi_init(struct
> acpi_table_header *table)
> }
> TIMER_ACPI_DECLARE(arch_timer, ACPI_SIG_GTDT, arch_timer_acpi_init);
> #endif
> +
> +int kvm_arch_ptp_get_crosststamp(u64 *cycle, struct timespec64 *ts,
> + struct clocksource **cs)
> +{
> + struct arm_smccc_res hvc_res;
> + ktime_t ktime;
> + u32 ptp_counter;
> +
> + if (arch_timer_uses_ppi == ARCH_TIMER_VIRT_PPI)
> + ptp_counter = ARM_PTP_VIRT_COUNTER;
> + else
> + ptp_counter = ARM_PTP_PHY_COUNTER;
> +
> + arm_smccc_1_1_invoke(ARM_SMCCC_VENDOR_HYP_KVM_PTP_FUNC_ID,
> + ptp_counter, &hvc_res);
> +
> + if ((int)(hvc_res.a0) < 0)
> + return -EOPNOTSUPP;
> +
> + ktime = (u64)hvc_res.a0 << 32 | hvc_res.a1;
> + *ts = ktime_to_timespec64(ktime);
> + *cycle = (u64)hvc_res.a2 << 32 | hvc_res.a3;
Endianness.
> + *cs = &clocksource_counter;
> +
> + return 0;
> +}
> +EXPORT_SYMBOL_GPL(kvm_arch_ptp_get_crosststamp);
> diff --git a/drivers/ptp/Kconfig b/drivers/ptp/Kconfig
> index 942f72d8151d..677c7f696b70 100644
> --- a/drivers/ptp/Kconfig
> +++ b/drivers/ptp/Kconfig
> @@ -106,7 +106,7 @@ config PTP_1588_CLOCK_PCH
> config PTP_1588_CLOCK_KVM
> tristate "KVM virtual PTP clock"
> depends on PTP_1588_CLOCK
> - depends on KVM_GUEST && X86
> + depends on KVM_GUEST && X86 || (HAVE_ARM_SMCCC_DISCOVERY &&
> ARM_ARCH_TIMER)
> default y
> help
> This driver adds support for using kvm infrastructure as a PTP
> diff --git a/drivers/ptp/Makefile b/drivers/ptp/Makefile
> index 699a4e4d19c2..9fa5ede44b2b 100644
> --- a/drivers/ptp/Makefile
> +++ b/drivers/ptp/Makefile
> @@ -5,6 +5,7 @@
>
> ptp-y := ptp_clock.o ptp_chardev.o ptp_sysfs.o
> ptp_kvm-$(CONFIG_X86) := ptp_kvm_x86.o ptp_kvm_common.o
> +ptp_kvm-$(CONFIG_HAVE_ARM_SMCCC) := ptp_kvm_arm.o ptp_kvm_common.o
> obj-$(CONFIG_PTP_1588_CLOCK) += ptp.o
> obj-$(CONFIG_PTP_1588_CLOCK_DTE) += ptp_dte.o
> obj-$(CONFIG_PTP_1588_CLOCK_INES) += ptp_ines.o
> diff --git a/drivers/ptp/ptp_kvm_arm.c b/drivers/ptp/ptp_kvm_arm.c
> new file mode 100644
> index 000000000000..2212827c0384
> --- /dev/null
> +++ b/drivers/ptp/ptp_kvm_arm.c
> @@ -0,0 +1,44 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Virtual PTP 1588 clock for use with KVM guests
> + * Copyright (C) 2019 ARM Ltd.
> + * All Rights Reserved
> + */
> +
> +#include <linux/kernel.h>
> +#include <linux/err.h>
> +#include <asm/hypervisor.h>
> +#include <linux/module.h>
> +#include <linux/psci.h>
> +#include <linux/arm-smccc.h>
> +#include <linux/timecounter.h>
> +#include <linux/sched/clock.h>
> +#include <asm/arch_timer.h>
> +#include <asm/hypervisor.h>
> +
> +int kvm_arch_ptp_init(void)
> +{
> + int ret;
> +
> + ret = kvm_arm_hyp_service_available(ARM_SMCCC_KVM_FUNC_KVM_PTP);
> + if (ret <= 0)
> + return -EOPNOTSUPP;
> +
> + return 0;
> +}
> +
> +int kvm_arch_ptp_get_clock(struct timespec64 *ts)
> +{
> + ktime_t ktime;
> + struct arm_smccc_res hvc_res;
> +
> + arm_smccc_1_1_invoke(ARM_SMCCC_VENDOR_HYP_KVM_PTP_FUNC_ID,
> + ARM_PTP_NONE_COUNTER, &hvc_res);
I really don't see the need to use a non-architectural counter ID.
Using the virtual counter ID should just be fine, and shouldn't
lead to any issue.
Am I missing something?
> + if ((int)(hvc_res.a0) < 0)
> + return -EOPNOTSUPP;
> +
> + ktime = (u64)hvc_res.a0 << 32 | hvc_res.a1;
Endianness.
> + *ts = ktime_to_timespec64(ktime);
> +
> + return 0;
> +}
Thanks,
M.
--
Jazz is not dead. It just smells funny...
Hi Marc,
> -----Original Message-----
> From: Marc Zyngier <[email protected]>
> Sent: Monday, November 23, 2020 6:49 PM
> To: Jianyong Wu <[email protected]>
> Cc: [email protected]; [email protected]; [email protected];
> [email protected]; [email protected]; [email protected];
> [email protected]; Mark Rutland <[email protected]>;
> [email protected]; Suzuki Poulose <[email protected]>; Andre
> Przywara <[email protected]>; Steven Price
> <[email protected]>; [email protected]; linux-arm-
> [email protected]; [email protected];
> [email protected]; Steve Capper <[email protected]>; Justin He
> <[email protected]>; nd <[email protected]>
> Subject: Re: [PATCH v15 7/9] ptp: arm/arm64: Enable ptp_kvm for
> arm/arm64
>
> On 2020-11-11 06:22, Jianyong Wu wrote:
> > Currently, there is no mechanism to keep time sync between guest and
> > host in arm/arm64 virtualization environment. Time in guest will drift
> > compared with host after boot up as they may both use third party time
> > sources to correct their time respectively. The time deviation will be
> > in order of milliseconds. But in some scenarios,like in cloud
> > envirenment, we ask
>
> environment
>
OK
> > for higher time precision.
> >
> > kvm ptp clock, which chooses the host clock source as a reference
> > clock to sync time between guest and host, has been adopted by x86
> > which takes the time sync order from milliseconds to nanoseconds.
> >
> > This patch enables kvm ptp clock for arm/arm64 and improves clock sync
> > precison
>
> precision
>
OK
> > significantly.
> >
> > Test result comparisons between with kvm ptp clock and without it in
> > arm/arm64
> > are as follows. This test derived from the result of command 'chronyc
> > sources'. we should take more care of the last sample column which
> > shows the offset between the local clock and the source at the last
> > measurement.
> >
> > no kvm ptp in guest:
> > MS Name/IP address Stratum Poll Reach LastRx Last sample
> >
> ==========================================================
> ==============
> > ^* dns1.synet.edu.cn 2 6 377 13 +1040us[+1581us] +/-
> > 21ms
> > ^* dns1.synet.edu.cn 2 6 377 21 +1040us[+1581us] +/-
> > 21ms
> > ^* dns1.synet.edu.cn 2 6 377 29 +1040us[+1581us] +/-
> > 21ms
> > ^* dns1.synet.edu.cn 2 6 377 37 +1040us[+1581us] +/-
> > 21ms
> > ^* dns1.synet.edu.cn 2 6 377 45 +1040us[+1581us] +/-
> > 21ms
> > ^* dns1.synet.edu.cn 2 6 377 53 +1040us[+1581us] +/-
> > 21ms
> > ^* dns1.synet.edu.cn 2 6 377 61 +1040us[+1581us] +/-
> > 21ms
> > ^* dns1.synet.edu.cn 2 6 377 4 -130us[ +796us] +/-
> > 21ms
> > ^* dns1.synet.edu.cn 2 6 377 12 -130us[ +796us] +/-
> > 21ms
> > ^* dns1.synet.edu.cn 2 6 377 20 -130us[ +796us] +/-
> > 21ms
> >
> > in host:
> > MS Name/IP address Stratum Poll Reach LastRx Last sample
> >
> ==========================================================
> ==============
> > ^* 120.25.115.20 2 7 377 72 -470us[ -603us] +/-
> > 18ms
> > ^* 120.25.115.20 2 7 377 92 -470us[ -603us] +/-
> > 18ms
> > ^* 120.25.115.20 2 7 377 112 -470us[ -603us] +/-
> > 18ms
> > ^* 120.25.115.20 2 7 377 2 +872ns[-6808ns] +/-
> > 17ms
> > ^* 120.25.115.20 2 7 377 22 +872ns[-6808ns] +/-
> > 17ms
> > ^* 120.25.115.20 2 7 377 43 +872ns[-6808ns] +/-
> > 17ms
> > ^* 120.25.115.20 2 7 377 63 +872ns[-6808ns] +/-
> > 17ms
> > ^* 120.25.115.20 2 7 377 83 +872ns[-6808ns] +/-
> > 17ms
> > ^* 120.25.115.20 2 7 377 103 +872ns[-6808ns] +/-
> > 17ms
> > ^* 120.25.115.20 2 7 377 123 +872ns[-6808ns] +/-
> > 17ms
> >
> > The dns1.synet.edu.cn is the network reference clock for guest and
> > 120.25.115.20 is the network reference clock for host. we can't get
> > the clock error between guest and host directly, but a roughly
> > estimated value will be in order of hundreds of us to ms.
> >
> > with kvm ptp in guest:
> > chrony has been disabled in host to remove the disturb by network
> > clock.
> >
> > MS Name/IP address Stratum Poll Reach LastRx Last sample
> >
> ==========================================================
> ==============
> > * PHC0 0 3 377 8 -7ns[ +1ns] +/-
> > 3ns
> > * PHC0 0 3 377 8 +1ns[ +16ns] +/-
> > 3ns
> > * PHC0 0 3 377 6 -4ns[ -0ns] +/-
> > 6ns
> > * PHC0 0 3 377 6 -8ns[ -12ns] +/-
> > 5ns
> > * PHC0 0 3 377 5 +2ns[ +4ns] +/-
> > 4ns
> > * PHC0 0 3 377 13 +2ns[ +4ns] +/-
> > 4ns
> > * PHC0 0 3 377 12 -4ns[ -6ns] +/-
> > 4ns
> > * PHC0 0 3 377 11 -8ns[ -11ns] +/-
> > 6ns
> > * PHC0 0 3 377 10 -14ns[ -20ns] +/-
> > 4ns
> > * PHC0 0 3 377 8 +4ns[ +5ns] +/-
> > 4ns
> >
> > The PHC0 is the ptp clock which choose the host clock as its source
> > clock. So we can see that the clock difference between host and guest
> > is in order of ns.
> >
> > Signed-off-by: Jianyong Wu <[email protected]>
> > ---
> > drivers/clocksource/arm_arch_timer.c | 28 ++++++++++++++++++
> > drivers/ptp/Kconfig | 2 +-
> > drivers/ptp/Makefile | 1 +
> > drivers/ptp/ptp_kvm_arm.c | 44
> ++++++++++++++++++++++++++++
> > 4 files changed, 74 insertions(+), 1 deletion(-) create mode 100644
> > drivers/ptp/ptp_kvm_arm.c
> >
> > diff --git a/drivers/clocksource/arm_arch_timer.c
> > b/drivers/clocksource/arm_arch_timer.c
> > index d55acffb0b90..b33c5a663d30 100644
> > --- a/drivers/clocksource/arm_arch_timer.c
> > +++ b/drivers/clocksource/arm_arch_timer.c
> > @@ -25,6 +25,7 @@
> > #include <linux/sched/clock.h>
> > #include <linux/sched_clock.h>
> > #include <linux/acpi.h>
> > +#include <linux/arm-smccc.h>
> >
> > #include <asm/arch_timer.h>
> > #include <asm/virt.h>
> > @@ -1650,3 +1651,30 @@ static int __init arch_timer_acpi_init(struct
> > acpi_table_header *table) } TIMER_ACPI_DECLARE(arch_timer,
> > ACPI_SIG_GTDT, arch_timer_acpi_init); #endif
> > +
> > +int kvm_arch_ptp_get_crosststamp(u64 *cycle, struct timespec64 *ts,
> > + struct clocksource **cs)
> > +{
> > + struct arm_smccc_res hvc_res;
> > + ktime_t ktime;
> > + u32 ptp_counter;
> > +
> > + if (arch_timer_uses_ppi == ARCH_TIMER_VIRT_PPI)
> > + ptp_counter = ARM_PTP_VIRT_COUNTER;
> > + else
> > + ptp_counter = ARM_PTP_PHY_COUNTER;
> > +
> > +
> arm_smccc_1_1_invoke(ARM_SMCCC_VENDOR_HYP_KVM_PTP_FU
> NC_ID,
> > + ptp_counter, &hvc_res);
> > +
> > + if ((int)(hvc_res.a0) < 0)
> > + return -EOPNOTSUPP;
> > +
> > + ktime = (u64)hvc_res.a0 << 32 | hvc_res.a1;
> > + *ts = ktime_to_timespec64(ktime);
> > + *cycle = (u64)hvc_res.a2 << 32 | hvc_res.a3;
>
> Endianness.
>
> > + *cs = &clocksource_counter;
> > +
> > + return 0;
> > +}
> > +EXPORT_SYMBOL_GPL(kvm_arch_ptp_get_crosststamp);
> > diff --git a/drivers/ptp/Kconfig b/drivers/ptp/Kconfig index
> > 942f72d8151d..677c7f696b70 100644
> > --- a/drivers/ptp/Kconfig
> > +++ b/drivers/ptp/Kconfig
> > @@ -106,7 +106,7 @@ config PTP_1588_CLOCK_PCH config
> > PTP_1588_CLOCK_KVM
> > tristate "KVM virtual PTP clock"
> > depends on PTP_1588_CLOCK
> > - depends on KVM_GUEST && X86
> > + depends on KVM_GUEST && X86 ||
> (HAVE_ARM_SMCCC_DISCOVERY &&
> > ARM_ARCH_TIMER)
> > default y
> > help
> > This driver adds support for using kvm infrastructure as a PTP
> > diff --git a/drivers/ptp/Makefile b/drivers/ptp/Makefile index
> > 699a4e4d19c2..9fa5ede44b2b 100644
> > --- a/drivers/ptp/Makefile
> > +++ b/drivers/ptp/Makefile
> > @@ -5,6 +5,7 @@
> >
> > ptp-y := ptp_clock.o ptp_chardev.o
> ptp_sysfs.o
> > ptp_kvm-$(CONFIG_X86) := ptp_kvm_x86.o
> ptp_kvm_common.o
> > +ptp_kvm-$(CONFIG_HAVE_ARM_SMCCC) := ptp_kvm_arm.o
> ptp_kvm_common.o
> > obj-$(CONFIG_PTP_1588_CLOCK) += ptp.o
> > obj-$(CONFIG_PTP_1588_CLOCK_DTE) += ptp_dte.o
> > obj-$(CONFIG_PTP_1588_CLOCK_INES) += ptp_ines.o
> > diff --git a/drivers/ptp/ptp_kvm_arm.c b/drivers/ptp/ptp_kvm_arm.c new
> > file mode 100644 index 000000000000..2212827c0384
> > --- /dev/null
> > +++ b/drivers/ptp/ptp_kvm_arm.c
> > @@ -0,0 +1,44 @@
> > +// SPDX-License-Identifier: GPL-2.0-only
> > +/*
> > + * Virtual PTP 1588 clock for use with KVM guests
> > + * Copyright (C) 2019 ARM Ltd.
> > + * All Rights Reserved
> > + */
> > +
> > +#include <linux/kernel.h>
> > +#include <linux/err.h>
> > +#include <asm/hypervisor.h>
> > +#include <linux/module.h>
> > +#include <linux/psci.h>
> > +#include <linux/arm-smccc.h>
> > +#include <linux/timecounter.h>
> > +#include <linux/sched/clock.h>
> > +#include <asm/arch_timer.h>
> > +#include <asm/hypervisor.h>
> > +
> > +int kvm_arch_ptp_init(void)
> > +{
> > + int ret;
> > +
> > + ret =
> kvm_arm_hyp_service_available(ARM_SMCCC_KVM_FUNC_KVM_PTP);
> > + if (ret <= 0)
> > + return -EOPNOTSUPP;
> > +
> > + return 0;
> > +}
> > +
> > +int kvm_arch_ptp_get_clock(struct timespec64 *ts) {
> > + ktime_t ktime;
> > + struct arm_smccc_res hvc_res;
> > +
> > +
> arm_smccc_1_1_invoke(ARM_SMCCC_VENDOR_HYP_KVM_PTP_FU
> NC_ID,
> > + ARM_PTP_NONE_COUNTER, &hvc_res);
>
> I really don't see the need to use a non-architectural counter ID.
> Using the virtual counter ID should just be fine, and shouldn't lead to any
> issue.
>
> Am I missing something?
In this function, no counter data is needed. If virtual counter ID is used here, user may be confused with why we get virtual counter
data and do nothing with it. So I explicitly add a new "NONE" counter ID to make it clear.
WDYT?
Thanks
Jianyong
>
> > + if ((int)(hvc_res.a0) < 0)
> > + return -EOPNOTSUPP;
> > +
> > + ktime = (u64)hvc_res.a0 << 32 | hvc_res.a1;
>
> Endianness.
>
> > + *ts = ktime_to_timespec64(ktime);
> > +
> > + return 0;
> > +}
>
> Thanks,
>
> M.
> --
> Jazz is not dead. It just smells funny...
Jianyong,
On 2020-11-24 05:37, Jianyong Wu wrote:
> Hi Marc,
[...]
>> > +
>> arm_smccc_1_1_invoke(ARM_SMCCC_VENDOR_HYP_KVM_PTP_FU
>> NC_ID,
>> > + ARM_PTP_NONE_COUNTER, &hvc_res);
>>
>> I really don't see the need to use a non-architectural counter ID.
>> Using the virtual counter ID should just be fine, and shouldn't lead
>> to any
>> issue.
>>
>
>> Am I missing something?
>
> In this function, no counter data is needed. If virtual counter ID is
> used here, user may be confused with why we get virtual counter
> data and do nothing with it. So I explicitly add a new "NONE" counter
> ID to make it clear.
>
> WDYT?
ITIABI (I Think It's A Bad Idea). There are two counters, and the API
allows to retrieve the data for any of these two. If the "user" doesn't
want to do anything with the data, that's their problem.
Here, you can just sue the virtual counter, and that will give you the
exact same semantic, without inventing non-architectural state.
Thanks,
M.
--
Jazz is not dead. It just smells funny...
Hi Marc,
> -----Original Message-----
> From: Marc Zyngier <[email protected]>
> Sent: Tuesday, November 24, 2020 5:05 PM
> To: Jianyong Wu <[email protected]>
> Cc: [email protected]; [email protected]; [email protected];
> [email protected]; [email protected]; [email protected];
> [email protected]; Mark Rutland <[email protected]>;
> [email protected]; Suzuki Poulose <[email protected]>; Andre
> Przywara <[email protected]>; Steven Price
> <[email protected]>; [email protected]; linux-arm-
> [email protected]; [email protected];
> [email protected]; Steve Capper <[email protected]>; Justin He
> <[email protected]>; nd <[email protected]>
> Subject: Re: [PATCH v15 7/9] ptp: arm/arm64: Enable ptp_kvm for
> arm/arm64
>
> Jianyong,
>
> On 2020-11-24 05:37, Jianyong Wu wrote:
> > Hi Marc,
>
> [...]
>
> >> > +
> >> arm_smccc_1_1_invoke(ARM_SMCCC_VENDOR_HYP_KVM_PTP_FU
> >> NC_ID,
> >> > + ARM_PTP_NONE_COUNTER, &hvc_res);
> >>
> >> I really don't see the need to use a non-architectural counter ID.
> >> Using the virtual counter ID should just be fine, and shouldn't lead
> >> to any issue.
> >>
> >
> >> Am I missing something?
> >
> > In this function, no counter data is needed. If virtual counter ID is
> > used here, user may be confused with why we get virtual counter
> > data and do nothing with it. So I explicitly add a new "NONE" counter
> > ID to make it clear.
> >
> > WDYT?
>
> ITIABI (I Think It's A Bad Idea). There are two counters, and the API
> allows to retrieve the data for any of these two. If the "user" doesn't
> want to do anything with the data, that's their problem.
>
> Here, you can just sue the virtual counter, and that will give you the
> exact same semantic, without inventing non-architectural state.
>
OK, that's it.
Thanks
Jianyong Wu
> Thanks,
>
> M.
> --
> Jazz is not dead. It just smells funny...