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[46.138.151.163]) by smtp.gmail.com with ESMTPSA id m21sm382496lfe.29.2016.01.21.11.04.42 (version=TLS1_2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Thu, 21 Jan 2016 11:04:43 -0800 (PST) From: Dmitry Osipenko To: QEMU Developers , qemu-arm@nongnu.org Date: Thu, 21 Jan 2016 22:03:44 +0300 Message-Id: <73f8fa42b0af75594a2ec6a2fa13cf5d21fd2703.1453402860.git.digetx@gmail.com> X-Mailer: git-send-email 2.7.0 In-Reply-To: References: In-Reply-To: References: X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 2a00:1450:4010:c04::242 Cc: Peter Maydell , Peter Crosthwaite Subject: [Qemu-devel] [PATCH v11 1/7] hw/ptimer: Fix issues caused by the adjusted timer limit value X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Sender: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Multiple issues here related to the timer with a adjusted .limit value: 1) ptimer_get_count() returns incorrect counter value for the disabled timer after loading the counter with a small value, because adjusted limit value is used instead of the original. For instance: 1) ptimer_stop(t) 2) ptimer_set_period(t, 1) 3) ptimer_set_limit(t, 0, 1) 4) ptimer_get_count(t) <-- would return 10000 instead of 0 2) ptimer_get_count() might return incorrect value for the timer running with a adjusted limit value. For instance: 1) ptimer_stop(t) 2) ptimer_set_period(t, 1) 3) ptimer_set_limit(t, 10, 1) 4) ptimer_run(t) 5) ptimer_get_count(t) <-- might return value > 10 3) Neither ptimer_set_period() nor ptimer_set_freq() are adjusting the limit value, so it is still possible to make timer timeout value arbitrary small. For instance: 1) ptimer_set_period(t, 10000) 2) ptimer_set_limit(t, 1, 0) 3) ptimer_set_period(t, 1) <-- bypass limit correction Fix all of the above issues by adjusting timer period instead of the limit. Perform the adjustment for periodic timer only. Use the delta value instead of the limit to make decision whether adjustment is required, as limit could be altered while timer is running, resulting in incorrect value returned by ptimer_get_count. Signed-off-by: Dmitry Osipenko Reviewed-by: Peter Crosthwaite --- hw/core/ptimer.c | 51 +++++++++++++++++++++++++++++++-------------------- 1 file changed, 31 insertions(+), 20 deletions(-) diff --git a/hw/core/ptimer.c b/hw/core/ptimer.c index edf077c..6dc1677 100644 --- a/hw/core/ptimer.c +++ b/hw/core/ptimer.c @@ -34,6 +34,9 @@ static void ptimer_trigger(ptimer_state *s) static void ptimer_reload(ptimer_state *s) { + uint32_t period_frac = s->period_frac; + uint64_t period = s->period; + if (s->delta == 0) { ptimer_trigger(s); s->delta = s->limit; @@ -44,10 +47,24 @@ static void ptimer_reload(ptimer_state *s) return; } + /* + * Artificially limit timeout rate to something + * achievable under QEMU. Otherwise, QEMU spends all + * its time generating timer interrupts, and there + * is no forward progress. + * About ten microseconds is the fastest that really works + * on the current generation of host machines. + */ + + if ((s->enabled == 1) && (s->delta * period < 10000) && !use_icount) { + period = 10000 / s->delta; + period_frac = 0; + } + s->last_event = s->next_event; - s->next_event = s->last_event + s->delta * s->period; - if (s->period_frac) { - s->next_event += ((int64_t)s->period_frac * s->delta) >> 32; + s->next_event = s->last_event + s->delta * period; + if (period_frac) { + s->next_event += ((int64_t)period_frac * s->delta) >> 32; } timer_mod(s->timer, s->next_event); } @@ -82,6 +99,13 @@ uint64_t ptimer_get_count(ptimer_state *s) uint64_t div; int clz1, clz2; int shift; + uint32_t period_frac = s->period_frac; + uint64_t period = s->period; + + if ((s->enabled == 1) && !use_icount && (s->delta * period < 10000)) { + period = 10000 / s->delta; + period_frac = 0; + } /* We need to divide time by period, where time is stored in rem (64-bit integer) and period is stored in period/period_frac @@ -94,7 +118,7 @@ uint64_t ptimer_get_count(ptimer_state *s) */ rem = s->next_event - now; - div = s->period; + div = period; clz1 = clz64(rem); clz2 = clz64(div); @@ -103,13 +127,13 @@ uint64_t ptimer_get_count(ptimer_state *s) rem <<= shift; div <<= shift; if (shift >= 32) { - div |= ((uint64_t)s->period_frac << (shift - 32)); + div |= ((uint64_t)period_frac << (shift - 32)); } else { if (shift != 0) - div |= (s->period_frac >> (32 - shift)); + div |= (period_frac >> (32 - shift)); /* Look at remaining bits of period_frac and round div up if necessary. */ - if ((uint32_t)(s->period_frac << shift)) + if ((uint32_t)(period_frac << shift)) div += 1; } counter = rem / div; @@ -181,19 +205,6 @@ void ptimer_set_freq(ptimer_state *s, uint32_t freq) count = limit. */ void ptimer_set_limit(ptimer_state *s, uint64_t limit, int reload) { - /* - * Artificially limit timeout rate to something - * achievable under QEMU. Otherwise, QEMU spends all - * its time generating timer interrupts, and there - * is no forward progress. - * About ten microseconds is the fastest that really works - * on the current generation of host machines. - */ - - if (!use_icount && limit * s->period < 10000 && s->period) { - limit = 10000 / s->period; - } - s->limit = limit; if (reload) s->delta = limit;