| Message ID | 1501331711-12961-6-git-send-email-dplotnikov@virtuozzo.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 29/07/2017 14:35, Denis Plotnikov wrote: > Now, L2 guests can't have a stable kvmclock while working over L1 with > a stable kvmclock. It is so just because of lack of functionality. > > The patch is a part of work making kvmclock stable in L2 if it works > over a stable kvmclock. > > Signed-off-by: Denis Plotnikov <dplotnikov@virtuozzo.com> > --- > arch/x86/kernel/pvclock.c | 19 ++++++++++++++++--- > 1 file changed, 16 insertions(+), 3 deletions(-) > > diff --git a/arch/x86/kernel/pvclock.c b/arch/x86/kernel/pvclock.c > index a2c554a..5b0bb2e 100644 > --- a/arch/x86/kernel/pvclock.c > +++ b/arch/x86/kernel/pvclock.c > @@ -22,6 +22,7 @@ > #include <linux/gfp.h> > #include <linux/bootmem.h> > #include <linux/nmi.h> > +#include <linux/cs_notifier.h> > > #include <asm/fixmap.h> > #include <asm/pvclock.h> > @@ -73,6 +74,8 @@ u8 pvclock_read_flags(struct pvclock_vcpu_time_info *src) > return flags & valid_flags; > } > > +static atomic64_t clocksource_stable = ATOMIC64_INIT(0); No need for atomic64. Otherwise looks good. Paolo > u64 pvclock_clocksource_read(struct pvclock_vcpu_time_info *src, u64 *cycles) > { > unsigned version; > @@ -96,10 +99,20 @@ u64 pvclock_clocksource_read(struct pvclock_vcpu_time_info *src, u64 *cycles) > pvclock_touch_watchdogs(); > } > > - if ((valid_flags & PVCLOCK_TSC_STABLE_BIT) && > - (flags & PVCLOCK_TSC_STABLE_BIT)) > - return ret; > + if (likely(valid_flags & PVCLOCK_TSC_STABLE_BIT)) { > + bool stable_now = !!(flags & PVCLOCK_TSC_STABLE_BIT); > + bool stable_last = (bool) atomic64_read(&clocksource_stable); > + > + if (unlikely(stable_now != stable_last)) { > + /* send notification once */ > + if (stable_last == atomic64_cmpxchg( > + &clocksource_stable, stable_last, stable_now)) > + clocksource_changes_notify(); > + } > > + if (stable_now) > + return ret; > + } > /* > * Assumption here is that last_value, a global accumulator, always goes > * forward. If we are less than that, we should not be much smaller. >
diff --git a/arch/x86/kernel/pvclock.c b/arch/x86/kernel/pvclock.c index a2c554a..5b0bb2e 100644 --- a/arch/x86/kernel/pvclock.c +++ b/arch/x86/kernel/pvclock.c @@ -22,6 +22,7 @@ #include <linux/gfp.h> #include <linux/bootmem.h> #include <linux/nmi.h> +#include <linux/cs_notifier.h> #include <asm/fixmap.h> #include <asm/pvclock.h> @@ -73,6 +74,8 @@ u8 pvclock_read_flags(struct pvclock_vcpu_time_info *src) return flags & valid_flags; } +static atomic64_t clocksource_stable = ATOMIC64_INIT(0); + u64 pvclock_clocksource_read(struct pvclock_vcpu_time_info *src, u64 *cycles) { unsigned version; @@ -96,10 +99,20 @@ u64 pvclock_clocksource_read(struct pvclock_vcpu_time_info *src, u64 *cycles) pvclock_touch_watchdogs(); } - if ((valid_flags & PVCLOCK_TSC_STABLE_BIT) && - (flags & PVCLOCK_TSC_STABLE_BIT)) - return ret; + if (likely(valid_flags & PVCLOCK_TSC_STABLE_BIT)) { + bool stable_now = !!(flags & PVCLOCK_TSC_STABLE_BIT); + bool stable_last = (bool) atomic64_read(&clocksource_stable); + + if (unlikely(stable_now != stable_last)) { + /* send notification once */ + if (stable_last == atomic64_cmpxchg( + &clocksource_stable, stable_last, stable_now)) + clocksource_changes_notify(); + } + if (stable_now) + return ret; + } /* * Assumption here is that last_value, a global accumulator, always goes * forward. If we are less than that, we should not be much smaller.
Now, L2 guests can't have a stable kvmclock while working over L1 with a stable kvmclock. It is so just because of lack of functionality. The patch is a part of work making kvmclock stable in L2 if it works over a stable kvmclock. Signed-off-by: Denis Plotnikov <dplotnikov@virtuozzo.com> --- arch/x86/kernel/pvclock.c | 19 ++++++++++++++++--- 1 file changed, 16 insertions(+), 3 deletions(-)