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Tue, 28 Apr 2026 03:15:47 -0700 (PDT) Date: Tue, 28 Apr 2026 11:15:46 +0100 From: Matt Fleming To: Corey Minyard Cc: Matt Fleming , openipmi-developer@lists.sourceforge.net, Tony Camuso , linux-kernel@vger.kernel.org, kernel-team@cloudflare.com, stable@vger.kernel.org Subject: Re: [PATCH 2/2] ipmi: Add limits to event and receive message requests Message-ID: References: <20260421132544.2666174-1-corey@minyard.net> <20260421132544.2666174-3-corey@minyard.net> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Sat, Apr 25, 2026 at 06:58:48PM -0500, Corey Minyard wrote: > > Oh, yeah. > > Moving it to handle_transaction_done() is not ideal, though. If > something was spewing receive messages, it would never get to events, > which is why I did it like I did. > > The following should fix this. You could also have different limits for > receive messages and events, but I think the following is more clear. > > diff --git a/drivers/char/ipmi/ipmi_si_intf.c b/drivers/char/ipmi/ipmi_si_intf.c > index 2a739123270c..e46f4150ceb5 100644 > --- a/drivers/char/ipmi/ipmi_si_intf.c > +++ b/drivers/char/ipmi/ipmi_si_intf.c > @@ -413,8 +413,10 @@ static void start_getting_msg_queue(struct smi_info *smi_info) > > start_new_msg(smi_info, smi_info->curr_msg->data, > smi_info->curr_msg->data_size); > - smi_info->num_requests_in_a_row = 0; > - smi_info->si_state = SI_GETTING_MESSAGES; > + if (smi_info->si_state != SI_GETTING_MESSAGES) { > + smi_info->num_requests_in_a_row = 0; > + smi_info->si_state = SI_GETTING_MESSAGES; > + } > } > > static void start_getting_events(struct smi_info *smi_info) > @@ -425,8 +427,10 @@ static void start_getting_events(struct smi_info *smi_info) > > start_new_msg(smi_info, smi_info->curr_msg->data, > smi_info->curr_msg->data_size); > - smi_info->num_requests_in_a_row = 0; > - smi_info->si_state = SI_GETTING_EVENTS; > + if (smi_info->si_state != SI_GETTING_EVENTS) { > + smi_info->num_requests_in_a_row = 0; > + smi_info->si_state = SI_GETTING_EVENTS; > + } Thanks. Does this correctly handle a stream of mixed receive+event flags, though? If we bounce between MESSAGES and EVENTS, won't we keep resetting the counter on each state transition and never hit the limit? I was able to cook up a simple repro in Qemu for this class of bug. ---->8---- diff --git a/hw/ipmi/ipmi_bmc_sim.c b/hw/ipmi/ipmi_bmc_sim.c index fd875491f5..127db30c03 100644 --- a/hw/ipmi/ipmi_bmc_sim.c +++ b/hw/ipmi/ipmi_bmc_sim.c @@ -249,6 +249,21 @@ struct IPMIBmcSim { uint8_t evtbuf[16]; QTAILQ_HEAD(, IPMIRcvBufEntry) rcvbufs; + + /* + * Fault injection: sticky EVENT_MSG_BUFFER_FULL. + * + * Simulates a BMC that continuously generates events (e.g. after a + * cold reset causes sensor state changes). Once armed, every + * READ_EVENT_MSG_BUFFER returns success but never clears the + * EVT_BUF_FULL flag, starving waiting_msg in the SI layer's + * handle_flags() loop. Reproduces the 517m277 / KRN-1233 wedge. + */ + bool fi_sticky_events; /* enable via property */ + uint32_t fi_evt_arm_after; /* arm after N completed responses */ + uint32_t fi_evt_rsp_count; /* responses completed so far */ + bool fi_evt_armed; /* fault is active */ + uint32_t fi_evt_read_count; /* READ_EVENT_MSG_BUFFER calls served */ }; #define IPMI_BMC_MSG_FLAG_WATCHDOG_TIMEOUT_MASK (1 << 3) @@ -494,7 +509,7 @@ static int sel_add_event(IPMIBmcSim *ibs, uint8_t *event) static int attn_set(IPMIBmcSim *ibs) { return IPMI_BMC_MSG_FLAG_RCV_MSG_QUEUE_SET(ibs) - || IPMI_BMC_MSG_FLAG_EVT_BUF_FULL_SET(ibs) + || (!ibs->fi_evt_armed && IPMI_BMC_MSG_FLAG_EVT_BUF_FULL_SET(ibs)) || IPMI_BMC_MSG_FLAG_WATCHDOG_TIMEOUT_MASK_SET(ibs); } @@ -750,6 +765,48 @@ static void ipmi_sim_handle_command(IPMIBmc *b, out: k->handle_rsp(s, msg_id, rsp.buffer, rsp.len); + /* + * Fault injection: count completed responses and arm sticky + * EVENT_MSG_BUFFER_FULL after the configured threshold. + */ + if (ibs->fi_sticky_events && !ibs->fi_evt_armed) { + ibs->fi_evt_rsp_count++; + if (ibs->fi_evt_rsp_count >= ibs->fi_evt_arm_after) { + ibs->fi_evt_armed = true; + ibs->fi_evt_read_count = 0; + + /* + * Seed the event buffer with a synthetic sensor event + * (sensor type 0x01 = Temperature, event type 0x01 = + * threshold, evd1 = upper critical going high). + * This matches what real BMCs generate after a cold reset. + */ + memset(ibs->evtbuf, 0, 16); + ibs->evtbuf[2] = 0x02; /* System event record */ + ibs->evtbuf[7] = ibs->parent.slave_addr; + ibs->evtbuf[9] = 0x04; /* Format version */ + ibs->evtbuf[10] = 0x01; /* Sensor type: Temperature */ + ibs->evtbuf[11] = 0x01; /* Sensor number */ + ibs->evtbuf[12] = 0x01; /* Event type: threshold */ + ibs->evtbuf[13] = 0x09; /* Upper critical going high */ + ibs->evtbuf[14] = 0x57; /* Threshold value */ + ibs->evtbuf[15] = 0x00; /* Sequence (incremented on reads) */ + + ibs->msg_flags |= IPMI_BMC_MSG_FLAG_EVT_BUF_FULL; + + /* Ensure event message buffer is enabled in global enables + * so the kernel sees it. Also enable event logging. + */ + ibs->bmc_global_enables |= (1 << IPMI_BMC_EVENT_MSG_BUF_BIT) + | (1 << IPMI_BMC_EVENT_LOG_BIT); + + k->set_atn(s, 1, attn_irq_enabled(ibs)); + + fprintf(stderr, "[FI] sticky-events armed after %u responses\n", + ibs->fi_evt_rsp_count); + } + } + next_timeout(ibs); } @@ -1013,8 +1070,14 @@ static void clr_msg_flags(IPMIBmcSim *ibs, { IPMIInterface *s = ibs->parent.intf; IPMIInterfaceClass *k = IPMI_INTERFACE_GET_CLASS(s); + uint8_t clear_mask = cmd[2]; + + if (ibs->fi_evt_armed) { + /* Don't allow clearing EVT_BUF_FULL when sticky events active */ + clear_mask &= ~IPMI_BMC_MSG_FLAG_EVT_BUF_FULL; + } - ibs->msg_flags &= ~cmd[2]; + ibs->msg_flags &= ~clear_mask; k->set_atn(s, attn_set(ibs), attn_irq_enabled(ibs)); } @@ -1040,7 +1103,19 @@ static void read_evt_msg_buf(IPMIBmcSim *ibs, for (i = 0; i < 16; i++) { rsp_buffer_push(rsp, ibs->evtbuf[i]); } - ibs->msg_flags &= ~IPMI_BMC_MSG_FLAG_EVT_BUF_FULL; + + if (ibs->fi_evt_armed) { + /* + * Sticky mode: return success but keep EVT_BUF_FULL set. + * Vary the event data slightly so the kernel doesn't + * de-duplicate (increment evd3 as a sequence number). + */ + ibs->fi_evt_read_count++; + ibs->evtbuf[15] = (uint8_t)(ibs->fi_evt_read_count & 0xff); + /* Don't clear the flag — starvation continues */ + } else { + ibs->msg_flags &= ~IPMI_BMC_MSG_FLAG_EVT_BUF_FULL; + } k->set_atn(s, attn_set(ibs), attn_irq_enabled(ibs)); } @@ -2670,6 +2745,8 @@ static const Property ipmi_sim_properties[] = { DEFINE_PROP_STRING("lan.netmask", IPMIBmcSim, lan.arg_netmask), DEFINE_PROP_STRING("lan.defgw_ipaddr", IPMIBmcSim, lan.arg_defgw_ipaddr), DEFINE_PROP_MACADDR("lan.defgw_macaddr", IPMIBmcSim, lan.defgw_macaddr), + DEFINE_PROP_BOOL("fi_sticky_events", IPMIBmcSim, fi_sticky_events, false), + DEFINE_PROP_UINT32("fi_evt_arm_after", IPMIBmcSim, fi_evt_arm_after, 40), }; static void ipmi_sim_class_init(ObjectClass *oc, const void *data)