From mboxrd@z Thu Jan 1 00:00:00 1970 From: Denis Plotnikov Subject: [PATCH v3 5/6] pvclock: add clocksource change notification on changing of tsc stable bit Date: Sat, 29 Jul 2017 15:35:10 +0300 Message-ID: <1501331711-12961-6-git-send-email-dplotnikov@virtuozzo.com> References: <1501331711-12961-1-git-send-email-dplotnikov@virtuozzo.com> Cc: rkagan@virtuozzo.com, den@virtuozzo.com, svt-core@lists.sw.ru To: pbonzini@redhat.com, rkrcmar@redhat.com, kvm@vger.kernel.org Return-path: Received: from mailhub.sw.ru ([195.214.232.25]:19113 "EHLO relay.sw.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753726AbdG2Mfy (ORCPT ); Sat, 29 Jul 2017 08:35:54 -0400 In-Reply-To: <1501331711-12961-1-git-send-email-dplotnikov@virtuozzo.com> Sender: kvm-owner@vger.kernel.org List-ID: 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 --- 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 #include #include +#include #include #include @@ -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. -- 2.7.4