Re: [PATCH v18 3/7] ptp: Reorganize ptp_kvm.c to make it arch-independent

Andre Przywara
2021-02-10T16:21:45Z

On Mon, 8 Feb 2021 13:40:25 +0000
Marc Zyngier <maz@kernel.org> wrote:

> From: Jianyong Wu <jianyong.wu@arm.com>
>
> Currently, the ptp_kvm module contains a lot of x86-specific code.
> Let's move this code into a new arch-specific file in the same directory,
> and rename the arch-independent file to ptp_kvm_common.c.
>
> Signed-off-by: Jianyong Wu <jianyong.wu@arm.com>
> Signed-off-by: Marc Zyngier <maz@kernel.org>
> Link: https://lore.kernel.org/r/20201209060932.212364-4-jianyong.wu@arm.com

Verified that the code movements are correct. Test compiled for x86.

1.5 nits below, but regardless:

Reviewed-by: Andre Przywara <andre.przywara@arm.com>

> ---
> drivers/ptp/Makefile | 1 +
> drivers/ptp/{ptp_kvm.c => ptp_kvm_common.c} | 84 +++++-------------
> drivers/ptp/ptp_kvm_x86.c | 97 +++++++++++++++++++++
> include/linux/ptp_kvm.h | 19 ++++
> 4 files changed, 139 insertions(+), 62 deletions(-)
> rename drivers/ptp/{ptp_kvm.c => ptp_kvm_common.c} (60%)
> create mode 100644 drivers/ptp/ptp_kvm_x86.c
> create mode 100644 include/linux/ptp_kvm.h
>
> diff --git a/drivers/ptp/Makefile b/drivers/ptp/Makefile
> index db5aef3bddc6..d11eeb5811d1 100644
> --- a/drivers/ptp/Makefile
> +++ b/drivers/ptp/Makefile
> @@ -4,6 +4,7 @@
> #
>
> ptp-y := ptp_clock.o ptp_chardev.o ptp_sysfs.o
> +ptp_kvm-$(CONFIG_X86) := ptp_kvm_x86.o ptp_kvm_common.o
> obj-$(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.c b/drivers/ptp/ptp_kvm_common.c
> similarity index 60%
> rename from drivers/ptp/ptp_kvm.c
> rename to drivers/ptp/ptp_kvm_common.c
> index 658d33fc3195..721ddcede5e1 100644
> --- a/drivers/ptp/ptp_kvm.c
> +++ b/drivers/ptp/ptp_kvm_common.c
> @@ -8,11 +8,11 @@
> #include <linux/err.h>
> #include <linux/init.h>
> #include <linux/kernel.h>
> +#include <linux/slab.h>
> #include <linux/module.h>
> +#include <linux/ptp_kvm.h>
> #include <uapi/linux/kvm_para.h>
> #include <asm/kvm_para.h>
> -#include <asm/pvclock.h>
> -#include <asm/kvmclock.h>
> #include <uapi/asm/kvm_para.h>
>
> #include <linux/ptp_clock_kernel.h>
> @@ -24,56 +24,29 @@ struct kvm_ptp_clock {
>
> static DEFINE_SPINLOCK(kvm_ptp_lock);
>
> -static struct pvclock_vsyscall_time_info *hv_clock;
> -
> -static struct kvm_clock_pairing clock_pair;
> -static phys_addr_t clock_pair_gpa;
> -
> static int ptp_kvm_get_time_fn(ktime_t *device_time,
> struct system_counterval_t *system_counter,
> void *ctx)
> {
> - unsigned long ret;
> + long ret;
> + u64 cycle;
> struct timespec64 tspec;
> - unsigned version;
> - int cpu;
> - struct pvclock_vcpu_time_info *src;
> + struct clocksource *cs;
>
> spin_lock(&kvm_ptp_lock);
>
> preempt_disable_notrace();
> - cpu = smp_processor_id();
> - src = &hv_clock[cpu].pvti;
> -
> - do {
> - /*
> - * We are using a TSC value read in the hosts
> - * kvm_hc_clock_pairing handling.
> - * So any changes to tsc_to_system_mul
> - * and tsc_shift or any other pvclock
> - * data invalidate that measurement.
> - */
> - version = pvclock_read_begin(src);
> -
> - ret = kvm_hypercall2(KVM_HC_CLOCK_PAIRING,
> - clock_pair_gpa,
> - KVM_CLOCK_PAIRING_WALLCLOCK);
> - if (ret != 0) {
> - pr_err_ratelimited("clock pairing hypercall ret %lu\n", ret);
> - spin_unlock(&kvm_ptp_lock);
> - preempt_enable_notrace();
> - return -EOPNOTSUPP;
> - }
> -
> - tspec.tv_sec = clock_pair.sec;
> - tspec.tv_nsec = clock_pair.nsec;
> - ret = __pvclock_read_cycles(src, clock_pair.tsc);
> - } while (pvclock_read_retry(src, version));
> + ret = kvm_arch_ptp_get_crosststamp(&cycle, &tspec, &cs);
> + if (ret) {
> + spin_unlock(&kvm_ptp_lock);
> + preempt_enable_notrace();
> + return ret;
> + }
>
> preempt_enable_notrace();
>
> - system_counter->cycles = ret;
> - system_counter->cs = &kvm_clock;
> + system_counter->cycles = cycle;
> + system_counter->cs = cs;
>
> *device_time = timespec64_to_ktime(tspec);
>
> @@ -111,22 +84,17 @@ static int ptp_kvm_settime(struct ptp_clock_info *ptp,
>
> static int ptp_kvm_gettime(struct ptp_clock_info *ptp, struct timespec64 *ts)
> {
> - unsigned long ret;
> + long ret;
> struct timespec64 tspec;
>
> spin_lock(&kvm_ptp_lock);
>
> - ret = kvm_hypercall2(KVM_HC_CLOCK_PAIRING,
> - clock_pair_gpa,
> - KVM_CLOCK_PAIRING_WALLCLOCK);
> - if (ret != 0) {
> - pr_err_ratelimited("clock offset hypercall ret %lu\n", ret);
> + ret = kvm_arch_ptp_get_clock(&tspec);
> + if (ret) {
> spin_unlock(&kvm_ptp_lock);
> - return -EOPNOTSUPP;
> + return ret;
> }
>
> - tspec.tv_sec = clock_pair.sec;
> - tspec.tv_nsec = clock_pair.nsec;
> spin_unlock(&kvm_ptp_lock);
>
> memcpy(ts, &tspec, sizeof(struct timespec64));
> @@ -168,19 +136,11 @@ static int __init ptp_kvm_init(void)
> {
> long ret;
>
> - if (!kvm_para_available())
> - return -ENODEV;
> -
> - clock_pair_gpa = slow_virt_to_phys(&clock_pair);
> - hv_clock = pvclock_get_pvti_cpu0_va();
> -
> - if (!hv_clock)
> - return -ENODEV;
> -
> - ret = kvm_hypercall2(KVM_HC_CLOCK_PAIRING, clock_pair_gpa,
> - KVM_CLOCK_PAIRING_WALLCLOCK);
> - if (ret == -KVM_ENOSYS || ret == -KVM_EOPNOTSUPP)
> - return -ENODEV;
> + ret = kvm_arch_ptp_init();
> + if (ret) {
> + pr_err("fail to initialize ptp_kvm");
> + return ret;
> + }
>
> kvm_ptp_clock.caps = ptp_kvm_caps;
>
> diff --git a/drivers/ptp/ptp_kvm_x86.c b/drivers/ptp/ptp_kvm_x86.c
> new file mode 100644
> index 000000000000..82a6be9a7479
> --- /dev/null
> +++ b/drivers/ptp/ptp_kvm_x86.c
> @@ -0,0 +1,97 @@
> +// SPDX-License-Identifier: GPL-2.0-or-later
> +/*
> + * Virtual PTP 1588 clock for use with KVM guests
> + *
> + * Copyright (C) 2017 Red Hat Inc.
> + */
> +
> +#include <linux/device.h>
> +#include <linux/kernel.h>
> +#include <asm/pvclock.h>
> +#include <asm/kvmclock.h>
> +#include <linux/module.h>
> +#include <uapi/asm/kvm_para.h>
> +#include <uapi/linux/kvm_para.h>
> +#include <linux/ptp_clock_kernel.h>
> +#include <linux/ptp_kvm.h>
> +
> +struct pvclock_vsyscall_time_info *hv_clock;
> +
> +static phys_addr_t clock_pair_gpa;
> +static struct kvm_clock_pairing clock_pair;
> +
> +int kvm_arch_ptp_init(void)
> +{
> + long ret;
> +
> + if (!kvm_para_available())
> + return -ENODEV;
> +
> + clock_pair_gpa = slow_virt_to_phys(&clock_pair);
> + hv_clock = pvclock_get_pvti_cpu0_va();
> + if (!hv_clock)
> + return -ENODEV;
> +
> + ret = kvm_hypercall2(KVM_HC_CLOCK_PAIRING, clock_pair_gpa,
> + KVM_CLOCK_PAIRING_WALLCLOCK);
> + if (ret == -KVM_ENOSYS || ret == -KVM_EOPNOTSUPP)
> + return -ENODEV;
> +
> + return 0;
> +}
> +
> +int kvm_arch_ptp_get_clock(struct timespec64 *ts)
> +{
> + unsigned long ret;

Nit: The return value type of kvm_hypercall2 is signed, so you can use
just "long" here. The former code used unsigned because ret was re-used
again for another call. This is now gone.

> +
> + ret = kvm_hypercall2(KVM_HC_CLOCK_PAIRING,
> + clock_pair_gpa,
> + KVM_CLOCK_PAIRING_WALLCLOCK);
> + if (ret != 0) {
> + pr_err_ratelimited("clock offset hypercall ret %lu\n", ret);
> + return -EOPNOTSUPP;
> + }
> +
> + ts->tv_sec = clock_pair.sec;
> + ts->tv_nsec = clock_pair.nsec;
> +
> + return 0;
> +}
> +
> +int kvm_arch_ptp_get_crosststamp(u64 *cycle, struct timespec64 *tspec,
> + struct clocksource **cs)
> +{
> + unsigned long ret;

Same here.

Cheers,
Andre

> + unsigned int version;
> + int cpu;
> + struct pvclock_vcpu_time_info *src;
> +
> + cpu = smp_processor_id();
> + src = &hv_clock[cpu].pvti;
> +
> + do {
> + /*
> + * We are using a TSC value read in the hosts
> + * kvm_hc_clock_pairing handling.
> + * So any changes to tsc_to_system_mul
> + * and tsc_shift or any other pvclock
> + * data invalidate that measurement.
> + */
> + version = pvclock_read_begin(src);
> +
> + ret = kvm_hypercall2(KVM_HC_CLOCK_PAIRING,
> + clock_pair_gpa,
> + KVM_CLOCK_PAIRING_WALLCLOCK);
> + if (ret != 0) {
> + pr_err_ratelimited("clock pairing hypercall ret %lu\n", ret);
> + return -EOPNOTSUPP;
> + }
> + tspec->tv_sec = clock_pair.sec;
> + tspec->tv_nsec = clock_pair.nsec;
> + *cycle = __pvclock_read_cycles(src, clock_pair.tsc);
> + } while (pvclock_read_retry(src, version));
> +
> + *cs = &kvm_clock;
> +
> + return 0;
> +}
> diff --git a/include/linux/ptp_kvm.h b/include/linux/ptp_kvm.h
> new file mode 100644
> index 000000000000..f960a719f0d5
> --- /dev/null
> +++ b/include/linux/ptp_kvm.h
> @@ -0,0 +1,19 @@
> +/* SPDX-License-Identifier: GPL-2.0-or-later */
> +/*
> + * Virtual PTP 1588 clock for use with KVM guests
> + *
> + * Copyright (C) 2017 Red Hat Inc.
> + */
> +
> +#ifndef _PTP_KVM_H_
> +#define _PTP_KVM_H_
> +
> +struct timespec64;
> +struct clocksource;
> +
> +int kvm_arch_ptp_init(void);
> +int kvm_arch_ptp_get_clock(struct timespec64 *ts);
> +int kvm_arch_ptp_get_crosststamp(u64 *cycle,
> + struct timespec64 *tspec, struct clocksource **cs);
> +
> +#endif /* _PTP_KVM_H_ */