From mboxrd@z Thu Jan 1 00:00:00 1970 From: Keir Fraser Subject: Re: [PATCH 2/4] x86/hvm: Run the RTC periodic timer on a consistent time series. Date: Thu, 28 Mar 2013 13:27:38 +0000 Message-ID: References: <1364476936-15824-3-git-send-email-tim@xen.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1364476936-15824-3-git-send-email-tim@xen.org> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Tim Deegan , xen-devel@lists.xen.org Cc: JBeulich@suse.com, suravee.suthikulpanit@amd.com List-Id: xen-devel@lists.xenproject.org On 28/03/2013 13:22, "Tim Deegan" wrote: > When the RTC periodic timer gets restarted, align it to the VM's boot > time, not to whatever time it is now. Otherwise every read of REG_C > will restart the current period > > Signed-off-by: Tim Deegan Looks rather sensible. Acked-by: Keir Fraser > --- > xen/arch/x86/hvm/rtc.c | 6 ++++-- > xen/include/asm-x86/hvm/vpt.h | 3 ++- > 2 files changed, 6 insertions(+), 3 deletions(-) > > diff --git a/xen/arch/x86/hvm/rtc.c b/xen/arch/x86/hvm/rtc.c > index 368d3c8..710ae89 100644 > --- a/xen/arch/x86/hvm/rtc.c > +++ b/xen/arch/x86/hvm/rtc.c > @@ -91,7 +91,7 @@ void rtc_periodic_interrupt(void *opaque) > * RTC_RATE_SELECT settings */ > static void rtc_timer_update(RTCState *s) > { > - int period_code, period; > + int period_code, period, delta; > struct vcpu *v = vrtc_vcpu(s); > > ASSERT(spin_is_locked(&s->lock)); > @@ -109,7 +109,8 @@ static void rtc_timer_update(RTCState *s) > { > period = 1 << (period_code - 1); /* period in 32 Khz cycles */ > period = DIV_ROUND(period * 1000000000ULL, 32768); /* in ns */ > - create_periodic_time(v, &s->pt, period, period, RTC_IRQ, NULL, > s); > + delta = period - ((NOW() - s->start_time) % period); > + create_periodic_time(v, &s->pt, delta, period, RTC_IRQ, NULL, s); > break; > } > /* fall through */ > @@ -741,6 +742,7 @@ void rtc_init(struct domain *d) > s->hw.cmos_data[RTC_REG_D] = RTC_VRT; > > s->current_tm = gmtime(get_localtime(d)); > + s->start_time = NOW(); > > rtc_copy_date(s); > > diff --git a/xen/include/asm-x86/hvm/vpt.h b/xen/include/asm-x86/hvm/vpt.h > index c75297b..2e9c7d2 100644 > --- a/xen/include/asm-x86/hvm/vpt.h > +++ b/xen/include/asm-x86/hvm/vpt.h > @@ -104,8 +104,9 @@ typedef struct RTCState { > struct hvm_hw_rtc hw; > /* RTC's idea of the current time */ > struct tm current_tm; > + /* periodic timer */ > + s_time_t start_time; > /* second update */ > - int64_t next_second_time; > struct periodic_time pt; > /* update-ended timer */ > struct timer update_timer;