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Mon, 22 Jul 2024 05:06:00 -0700 (PDT) X-Google-Smtp-Source: AGHT+IHoi/zm0pSQtqSuvPv3mMzgrC2a/0wb5qN0c+vcSDZdCPIPcvGvxGg0SVbFUVc0slbqB3WUxQ== X-Received: by 2002:a17:907:944b:b0:a77:d0a0:ea74 with SMTP id a640c23a62f3a-a7a4bfa4f77mr438359566b.3.1721649959811; Mon, 22 Jul 2024 05:05:59 -0700 (PDT) Received: from avogadro.local ([151.95.101.29]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-a7a3c92308dsm419969166b.170.2024.07.22.05.05.58 for (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 22 Jul 2024 05:05:59 -0700 (PDT) From: Paolo Bonzini To: qemu-devel@nongnu.org Subject: [PATCH 7/7] hpet: avoid timer storms on periodic timers Date: Mon, 22 Jul 2024 14:05:41 +0200 Message-ID: <20240722120541.70790-8-pbonzini@redhat.com> X-Mailer: git-send-email 2.45.2 In-Reply-To: <20240722120541.70790-1-pbonzini@redhat.com> References: <20240722120541.70790-1-pbonzini@redhat.com> MIME-Version: 1.0 Received-SPF: pass client-ip=170.10.129.124; envelope-from=pbonzini@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -21 X-Spam_score: -2.2 X-Spam_bar: -- X-Spam_report: (-2.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.133, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org If the period is set to a value that is too low, there could be no time left to run the rest of QEMU. Do not trigger interrupts faster than 1 MHz. Signed-off-by: Paolo Bonzini --- hw/timer/hpet.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) diff --git a/hw/timer/hpet.c b/hw/timer/hpet.c index 1654b7cb8b8..471950adef1 100644 --- a/hw/timer/hpet.c +++ b/hw/timer/hpet.c @@ -59,6 +59,7 @@ typedef struct HPETTimer { /* timers */ uint8_t wrap_flag; /* timer pop will indicate wrap for one-shot 32-bit * mode. Next pop will be actual timer expiration. */ + uint64_t last; /* last value armed, to avoid timer storms */ } HPETTimer; struct HPETState { @@ -266,6 +267,7 @@ static int hpet_post_load(void *opaque, int version_id) for (i = 0; i < s->num_timers; i++) { HPETTimer *t = &s->timer[i]; t->cmp64 = hpet_calculate_cmp64(t, s->hpet_counter, t->cmp); + t->last = qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) - NANOSECONDS_PER_SECOND; } /* Recalculate the offset between the main counter and guest time */ if (!s->hpet_offset_saved) { @@ -364,8 +366,15 @@ static const VMStateDescription vmstate_hpet = { static void hpet_arm(HPETTimer *t, uint64_t tick) { - /* FIXME: Clamp period to reasonable min value? */ - timer_mod(t->qemu_timer, hpet_get_ns(t->state, tick)); + uint64_t ns = hpet_get_ns(t->state, tick); + + /* Clamp period to reasonable min value (1 us) */ + if (timer_is_periodic(t) && ns - t->last < 1000) { + ns = t->last + 1000; + } + + t->last = ns; + timer_mod(t->qemu_timer, ns); } /*