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Subject[RFC PATCH 8/9] arm/arm64: add mechanism to let user choose which counter to return
Date
In general, vm inside will use virtual counter compered with host use
phyical counter. But in some special scenarios, like nested virtualization,
phyical counter maybe used by vm. A interface added in ptp_kvm driver to
offer a mechanism to let user choose which counter should be return from
host.
To use this feature, you should call PTP_EXTTS_REQUEST(2) ioctl with flag
set bit PTP_KVM_ARM_PHY_COUNTER in its argument then call
PTP_SYS_OFFSET_PRECISE(2) ioctl to get the cross timestamp and phyical
counter will return. If the bit not set or no call for PTP_EXTTS_REQUEST2,
virtual counter will return by default.

Signed-off-by: Jianyong Wu <jianyong.wu@arm.com>
Suggested-by: Marc Zyngier <maz@kernel.org>
---
drivers/clocksource/arm_arch_timer.c | 11 ++++++++++-
drivers/ptp/ptp_chardev.c | 8 +++++++-
drivers/ptp/ptp_kvm_common.c | 7 ++++---
include/uapi/linux/ptp_clock.h | 4 +++-
4 files changed, 24 insertions(+), 6 deletions(-)

diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c
index b1bc8bd198c2..3e43d4e4885e 100644
--- a/drivers/clocksource/arm_arch_timer.c
+++ b/drivers/clocksource/arm_arch_timer.c
@@ -1634,7 +1634,16 @@ int kvm_arch_ptp_get_crosststamp(unsigned long *cycle, struct timespec64 *ts,
struct arm_smccc_res hvc_res;
ktime_t ktime_overall;

- arm_smccc_1_1_invoke(ARM_SMCCC_HYP_KVM_PTP_FUNC_ID, &hvc_res);
+ /*
+ * an argument will be passed by a0 to determine weather virtual
+ * counter or phyical counter should be passed back.
+ */
+ if (*ctx)
+ arm_smccc_1_1_invoke(ARM_SMCCC_HYP_KVM_PTP_FUNC_ID,
+ ARM_SMCCC_HYP_KVM_PTP_PHY, &hvc_res);
+ else
+ arm_smccc_1_1_invoke(ARM_SMCCC_HYP_KVM_PTP_FUNC_ID,
+ ARM_SMCCC_HYP_KVM_PTP_VIRT, &hvc_res);
if ((int)(hvc_res.a0) < 0)
return -EOPNOTSUPP;

diff --git a/drivers/ptp/ptp_chardev.c b/drivers/ptp/ptp_chardev.c
index 09c3f1e5382d..bd7b6a31b6cb 100644
--- a/drivers/ptp/ptp_chardev.c
+++ b/drivers/ptp/ptp_chardev.c
@@ -122,6 +122,7 @@ long ptp_ioctl(struct posix_clock *pc, unsigned int cmd, unsigned long arg)
struct ptp_pin_desc pd;
struct timespec64 ts;
int enable, err = 0;
+ static long flag;

switch (cmd) {

@@ -149,6 +150,11 @@ long ptp_ioctl(struct posix_clock *pc, unsigned int cmd, unsigned long arg)
err = -EFAULT;
break;
}
+ /*
+ * Tell driver to call for physical counter.
+ * This is only for arm.
+ */
+ flag = req.extts.flags & PTP_KVM_ARM_PHY_COUNTER;
if (cmd == PTP_EXTTS_REQUEST2) {
/* Tell the drivers to check the flags carefully. */
req.extts.flags |= PTP_STRICT_FLAGS;
@@ -226,7 +232,7 @@ long ptp_ioctl(struct posix_clock *pc, unsigned int cmd, unsigned long arg)
err = -EOPNOTSUPP;
break;
}
- err = ptp->info->getcrosststamp(ptp->info, &xtstamp, NULL);
+ err = ptp->info->getcrosststamp(ptp->info, &xtstamp, &flag);
if (err)
break;

diff --git a/drivers/ptp/ptp_kvm_common.c b/drivers/ptp/ptp_kvm_common.c
index 60442f70d3fc..20fbecef1f22 100644
--- a/drivers/ptp/ptp_kvm_common.c
+++ b/drivers/ptp/ptp_kvm_common.c
@@ -36,7 +36,7 @@ static int ptp_kvm_get_time_fn(ktime_t *device_time,
spin_lock(&kvm_ptp_lock);

preempt_disable_notrace();
- ret = kvm_arch_ptp_get_crosststamp(&cycle, &tspec, &cs);
+ ret = kvm_arch_ptp_get_crosststamp(&cycle, &tspec, &cs, ctx);
if (ret != 0) {
pr_err_ratelimited("clock pairing hypercall ret %lu\n", ret);
spin_unlock(&kvm_ptp_lock);
@@ -57,9 +57,10 @@ static int ptp_kvm_get_time_fn(ktime_t *device_time,
}

static int ptp_kvm_getcrosststamp(struct ptp_clock_info *ptp,
- struct system_device_crosststamp *xtstamp)
+ struct system_device_crosststamp *xtstamp,
+ long *flag)
{
- return get_device_system_crosststamp(ptp_kvm_get_time_fn, NULL,
+ return get_device_system_crosststamp(ptp_kvm_get_time_fn, flag,
NULL, xtstamp);
}

diff --git a/include/uapi/linux/ptp_clock.h b/include/uapi/linux/ptp_clock.h
index 9dc9d0079e98..71e388a82244 100644
--- a/include/uapi/linux/ptp_clock.h
+++ b/include/uapi/linux/ptp_clock.h
@@ -32,6 +32,7 @@
#define PTP_RISING_EDGE (1<<1)
#define PTP_FALLING_EDGE (1<<2)
#define PTP_STRICT_FLAGS (1<<3)
+#define PTP_KVM_ARM_PHY_COUNTER (1<<4)
#define PTP_EXTTS_EDGES (PTP_RISING_EDGE | PTP_FALLING_EDGE)

/*
@@ -40,7 +41,8 @@
#define PTP_EXTTS_VALID_FLAGS (PTP_ENABLE_FEATURE | \
PTP_RISING_EDGE | \
PTP_FALLING_EDGE | \
- PTP_STRICT_FLAGS)
+ PTP_STRICT_FLAGS | \
+ PTP_KVM_ARM_PHY_COUNTER)

/*
* flag fields valid for the original PTP_EXTTS_REQUEST ioctl.
--
2.17.1
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