[Devel] [PATCH RHEL8 COMMIT] ve: add per-ve CLOCK_MONOTONIC time via __vdso_gettimeofday()
Konstantin Khorenko
khorenko at virtuozzo.com
Thu Oct 29 14:17:10 MSK 2020
The commit is pushed to "branch-rh8-4.18.0-193.6.3.vz8.4.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh8-4.18.0-193.6.3.vz8.4.14
------>
commit af2c78f571e62ae91e6c0f8ef69a1f237892ea1f
Author: Andrey Ryabinin <aryabinin at virtuozzo.com>
Date: Thu Oct 29 14:17:10 2020 +0300
ve: add per-ve CLOCK_MONOTONIC time via __vdso_gettimeofday()
Make possible to read virtualized container's CLOCK_MONOTONIC time
via __vdso_gettimeofday(). Record containers start time in per-ve
vdso and substruct it from the host's time on clock read.
https://jira.sw.ru/browse/PSBM-121668
Signed-off-by: Andrey Ryabinin <aryabinin at virtuozzo.com>
Reviewed-by: Konstantin Khorenko <khorenko at virtuozzo.com>
khorenko@ notes:
1) effectively we store in vdso area the same ve->start_time value.
If a CT has been previously running, say 5 ns, we store in
ve->start_time value (now - 5), so later monotonic_abs_to_ve()
returns now - (ve->start_time) == now - (now - 5) == 5
2) introduced timespec_sub_ns() function has "inline" attribute - it is
fine.
The stock timespec_add_ns() has "__always_inline" attribute, but the
function is static, so there will be different copies of the function anyway
even if the function is used in other files.
3) timespec_sub_ns() is introduced for optimization:
if we use timespec_add_ns(ns)+monotonic_time_to_ve(), there will be
2 cycles of __iter_div_u64_rem().
===============================================
The original vz7 commit message (f7188f105626):
ve/vdso: virtualized monotonic gettime through vdso
We already have infrastructure for virtualized vdso, however we use
it only to change LINUX_VERSION_NAME in container. Simply store container's
start time - ve->start_timespec in vdso variable - VDSO64_ve_start_timespec,
and use it in __vdso_clock_gettime() to calculate container's monotonic time.
Make uts_arch_setup_additional_pages()/uts_prep_vdso_pages_locked() to always
setup new vdso, since previous policy to setup vdso only if uts_ns->name.releas
e
wouldn't work for virtualized __vdso_clock_gettime()
https://jira.sw.ru/browse/PSBM-66451
Signed-off-by: Andrey Ryabinin <aryabinin at virtuozzo.com>
Reviewed-by: Dmitry Safonov <dsafonov at virtuozzo.com>
---
arch/x86/entry/vdso/vclock_gettime.c | 27 +++++++++++++++++++++++----
arch/x86/entry/vdso/vdso2c.c | 1 +
arch/x86/include/asm/vdso.h | 1 +
kernel/ve/ve.c | 14 ++++++++++++++
4 files changed, 39 insertions(+), 4 deletions(-)
diff --git a/arch/x86/entry/vdso/vclock_gettime.c b/arch/x86/entry/vdso/vclock_gettime.c
index e48ca3afa091..be1de6c4cafa 100644
--- a/arch/x86/entry/vdso/vclock_gettime.c
+++ b/arch/x86/entry/vdso/vclock_gettime.c
@@ -24,6 +24,8 @@
#define gtod (&VVAR(vsyscall_gtod_data))
+u64 ve_start_time;
+
extern int __vdso_clock_gettime(clockid_t clock, struct timespec *ts);
extern int __vdso_gettimeofday(struct timeval *tv, struct timezone *tz);
extern time_t __vdso_time(time_t *t);
@@ -227,6 +229,21 @@ notrace static int __always_inline do_realtime(struct timespec *ts)
return mode;
}
+static inline void timespec_sub_ns(struct timespec *ts, u64 ns)
+{
+ if ((s64)ns <= 0) {
+ ts->tv_sec += __iter_div_u64_rem(-ns, NSEC_PER_SEC, &ns);
+ ts->tv_nsec = ns;
+ } else {
+ ts->tv_sec -= __iter_div_u64_rem(ns, NSEC_PER_SEC, &ns);
+ if (ns) {
+ ts->tv_sec--;
+ ns = NSEC_PER_SEC - ns;
+ }
+ ts->tv_nsec = ns;
+ }
+}
+
notrace static int __always_inline do_monotonic(struct timespec *ts)
{
unsigned long seq;
@@ -242,9 +259,7 @@ notrace static int __always_inline do_monotonic(struct timespec *ts)
ns >>= gtod->shift;
} while (unlikely(gtod_read_retry(gtod, seq)));
- ts->tv_sec += __iter_div_u64_rem(ns, NSEC_PER_SEC, &ns);
- ts->tv_nsec = ns;
-
+ timespec_sub_ns(ts, ve_start_time - ns);
return mode;
}
@@ -260,12 +275,16 @@ notrace static void do_realtime_coarse(struct timespec *ts)
notrace static void do_monotonic_coarse(struct timespec *ts)
{
+ u64 ns;
unsigned long seq;
+
do {
seq = gtod_read_begin(gtod);
ts->tv_sec = gtod->monotonic_time_coarse_sec;
- ts->tv_nsec = gtod->monotonic_time_coarse_nsec;
+ ns = gtod->monotonic_time_coarse_nsec;
} while (unlikely(gtod_read_retry(gtod, seq)));
+
+ timespec_sub_ns(ts, ve_start_time - ns);
}
notrace int __vdso_clock_gettime(clockid_t clock, struct timespec *ts)
diff --git a/arch/x86/entry/vdso/vdso2c.c b/arch/x86/entry/vdso/vdso2c.c
index 7fab0bd96ac1..c76141e9ca16 100644
--- a/arch/x86/entry/vdso/vdso2c.c
+++ b/arch/x86/entry/vdso/vdso2c.c
@@ -110,6 +110,7 @@ struct vdso_sym required_syms[] = {
{"__kernel_rt_sigreturn", true},
{"int80_landing_pad", true},
{"linux_version_code", true},
+ {"ve_start_time", true},
};
__attribute__((format(printf, 1, 2))) __attribute__((noreturn))
diff --git a/arch/x86/include/asm/vdso.h b/arch/x86/include/asm/vdso.h
index 92c7ac06828e..9c265f79a126 100644
--- a/arch/x86/include/asm/vdso.h
+++ b/arch/x86/include/asm/vdso.h
@@ -28,6 +28,7 @@ struct vdso_image {
long sym___kernel_vsyscall;
long sym_int80_landing_pad;
long sym_linux_version_code;
+ long sym_ve_start_time;
};
#ifdef CONFIG_X86_64
diff --git a/kernel/ve/ve.c b/kernel/ve/ve.c
index 060f9ecc477e..ba9732d8fce1 100644
--- a/kernel/ve/ve.c
+++ b/kernel/ve/ve.c
@@ -374,6 +374,17 @@ static int ve_start_kthreadd(struct ve_struct *ve)
return err;
}
+static void ve_set_vdso_time(struct ve_struct *ve, u64 time)
+{
+ u64 *vdso_start_time;
+
+ vdso_start_time = ve->vdso_64->data + ve->vdso_64->sym_ve_start_time;
+ *vdso_start_time = time;
+
+ vdso_start_time = ve->vdso_32->data + ve->vdso_32->sym_ve_start_time;
+ *vdso_start_time = time;
+}
+
/* under ve->op_sem write-lock */
static int ve_start_container(struct ve_struct *ve)
{
@@ -408,6 +419,8 @@ static int ve_start_container(struct ve_struct *ve)
if (ve->start_time == 0) {
ve->start_time = tsk->start_time;
ve->real_start_time = tsk->real_start_time;
+
+ ve_set_vdso_time(ve, ve->start_time);
}
/* The value is wrong, but it is never compared to process
* start times */
@@ -1030,6 +1043,7 @@ static ssize_t ve_ts_write(struct kernfs_open_file *of, char *buf,
case VE_CF_CLOCK_MONOTONIC:
now = ktime_get_ns();
target = &ve->start_time;
+ ve_set_vdso_time(ve, now - delta_ns);
break;
case VE_CF_CLOCK_BOOTBASED:
now = ktime_get_boot_ns();
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