Messages in this thread | | | Subject | Re: [PATCH arm/aspeed/ast2500 v2] ipmi: add an Aspeed KCS IPMI BMC driver | From | Corey Minyard <> | Date | Tue, 30 Jan 2018 18:52:37 -0600 |
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On 01/30/2018 06:02 PM, Wang, Haiyue wrote: > > > On 2018-01-30 21:49, Corey Minyard wrote: >> On 01/29/2018 07:57 AM, Wang, Haiyue wrote: >>> >>> >>> On 2018-01-26 22:48, Corey Minyard wrote: >>>> On 01/26/2018 12:08 AM, Wang, Haiyue wrote: >>>>> >>>>> >>>>> On 2018-01-25 01:48, Corey Minyard wrote: >>>>>> On 01/24/2018 10:06 AM, Haiyue Wang wrote: >>>>>>> The KCS (Keyboard Controller Style) interface is used to perform >>>>>>> in-band >>>>>>> IPMI communication between a server host and its BMC (BaseBoard >>>>>>> Management >>>>>>> Controllers). >>>>>>> >>>>>>> This driver exposes the KCS interface on ASpeed SOCs (AST2400 >>>>>>> and AST2500) >>>>>>> as a character device. Such SOCs are commonly used as BMCs and >>>>>>> this driver >>>>>>> implements the BMC side of the KCS interface. >>>>>>> >>>>>>> Signed-off-by: Haiyue Wang <haiyue.wang@linux.intel.com> >>>>>>> >>>>>>> --- >>>>>>> v1->v2 >>>>>>> >>>>>>> - Divide the driver into two parts, one handles the BMC KCS IPMI >>>>>>> 2.0 state; >>>>>>> the other handles the BMC KCS controller such as AST2500 IO >>>>>>> accessing. >>>>>>> - Use the spin lock APIs to handle the device file operations >>>>>>> and BMC chip >>>>>>> IRQ inferface for accessing the same KCS BMC data structure. >>>>>>> - Enhanced the phases handling of the KCS BMC. >>>>>>> - Unified the IOCTL definition for IPMI BMC, it will be used by >>>>>>> KCS and BT. >>>>>>> >>>>>>> --- >>>>>>> >>>>>>> + >>>>>>> +static void kcs_bmc_handle_data(struct kcs_bmc *kcs_bmc) >>>>>>> +{ >>>>>>> + u8 data; >>>>>>> + >>>>>>> + switch (kcs_bmc->phase) { >>>>>>> + case KCS_PHASE_WRITE: >>>>>>> + set_state(kcs_bmc, WRITE_STATE); >>>>>>> + >>>>>>> + /* set OBF before reading data */ >>>>>>> + write_data(kcs_bmc, KCS_ZERO_DATA); >>>>>>> + >>>>>>> + if (kcs_bmc->data_in_idx < KCS_MSG_BUFSIZ) >>>>>>> + kcs_bmc->data_in[kcs_bmc->data_in_idx++] = >>>>>>> + read_data(kcs_bmc); >>>> >>>> I missed this earlier, you need to issue a length error if the data >>>> is too large. >>>> >>>>>>> + break; >>>>>>> + >>>>>>> + case KCS_PHASE_WRITE_END: >>>>>>> + set_state(kcs_bmc, READ_STATE); >>>>>>> + >>>>>>> + if (kcs_bmc->data_in_idx < KCS_MSG_BUFSIZ) >>>>>>> + kcs_bmc->data_in[kcs_bmc->data_in_idx++] = >>>>>>> + read_data(kcs_bmc); >>>>>>> + >>>>>>> + kcs_bmc->phase = KCS_PHASE_WAIT_READ; >>>>>>> + if (kcs_bmc->running) { >>>>>> >>>>>> Why do you only do this when running is set? It won't hurt >>>>>> anything if it's not >>>>>> set. As it is, you have a race if something opens the device >>>>>> while this code >>>>>> runs. >>>>>> >>>>>> Also, don't set the state to wait read until the "write" has >>>>>> finished (userland has >>>>>> read the data out of the buffer. More on that later. >>>>>> >>>>> Understood. >>>>>>> + kcs_bmc->data_in_avail = true; >>>>>>> + wake_up_interruptible(&kcs_bmc->queue); >>>>>>> + } >>>>>>> + break; >>>>>>> + >>>>>>> + case KCS_PHASE_READ: >>>>>>> + if (kcs_bmc->data_out_idx == kcs_bmc->data_out_len) >>>>>>> + set_state(kcs_bmc, IDLE_STATE); >>>>>>> + >>>>>>> + data = read_data(kcs_bmc); >>>>>>> + if (data != KCS_CMD_READ_BYTE) { >>>>>>> + set_state(kcs_bmc, ERROR_STATE); >>>>>>> + write_data(kcs_bmc, KCS_ZERO_DATA); >>>>>>> + break; >>>>>>> + } >>>>>>> + >>>>>>> + if (kcs_bmc->data_out_idx == kcs_bmc->data_out_len) { >>>>>>> + write_data(kcs_bmc, KCS_ZERO_DATA); >>>>>>> + kcs_bmc->phase = KCS_PHASE_IDLE; >>>>>>> + break; >>>>>>> + } >>>>>>> + >>>>>>> + write_data(kcs_bmc, >>>>>>> + kcs_bmc->data_out[kcs_bmc->data_out_idx++]); >>>>>>> + break; >>>>>>> + >>>>>>> + case KCS_PHASE_ABORT_ERROR1: >>>>>>> + set_state(kcs_bmc, READ_STATE); >>>>>>> + >>>>>>> + /* Read the Dummy byte */ >>>>>>> + read_data(kcs_bmc); >>>>>>> + >>>>>>> + write_data(kcs_bmc, kcs_bmc->error); >>>>>>> + kcs_bmc->phase = KCS_PHASE_ABORT_ERROR2; >>>>>>> + break; >>>>>>> + >>>>>>> + case KCS_PHASE_ABORT_ERROR2: >>>>>>> + set_state(kcs_bmc, IDLE_STATE); >>>>>>> + >>>>>>> + /* Read the Dummy byte */ >>>>>>> + read_data(kcs_bmc); >>>>>>> + >>>>>>> + write_data(kcs_bmc, KCS_ZERO_DATA); >>>>>>> + kcs_bmc->phase = KCS_PHASE_IDLE; >>>>>>> + >>>>>>> + break; >>>>>>> + >>>>>>> + default: >>>>>>> + set_state(kcs_bmc, ERROR_STATE); >>>>>>> + >>>>>>> + /* Read the Dummy byte */ >>>>>>> + read_data(kcs_bmc); >>>>>>> + >>>>>>> + write_data(kcs_bmc, KCS_ZERO_DATA); >>>>>>> + break; >>>>>>> + } >>>>>>> +} >>>>>>> + >>>>>>> +static void kcs_bmc_handle_command(struct kcs_bmc *kcs_bmc) >>>>>>> +{ >>>>>>> + u8 cmd; >>>>>>> + >>>>>>> + set_state(kcs_bmc, WRITE_STATE); >>>>>>> + >>>>>>> + /* Dummy data to generate OBF */ >>>>>>> + write_data(kcs_bmc, KCS_ZERO_DATA); >>>>>>> + >>>>>>> + cmd = read_data(kcs_bmc); >>>>>> >>>>>> Shouldn't you check the phase in all the cases below and do error >>>>>> handling if the phase isn't correct? >>>>>> >>>>>> Similar thing if the device here isn't open. You need to handle >>>>>> that gracefully. >>>>>> >>>>>> Also, you should remove data_in_avail and data_in_idx setting from >>>>>> here, for reasons I will explain later. >>>>>> >>>>> If host software sends the data twice such as a retry before the >>>>> BMC's IPMI service starts, >>>>> then the two IPMI requests will be merged into one, if not clear >>>>> data_in_idx after receving >>>>> KCS_CMD_WRITE_START. Most of the states are driven by host >>>>> software (SMS). :( >>>> >>>> True, but what if the host issues WRITE_START or a WRITE_END while >>>> this driver is in read >>>> state? The spec is unclear on this, but it really only makes sense >>>> for the host to issue >>>> WRITE_START in idle stat and WRITE_END in write state. IMHO it >>>> should go to error >>>> state. You might make the case that a WRITE_START anywhere >>>> restarts the transaction, >>>> but the feel of the error state machine kind of goes against that. >>>> WRITE_END is definitely >>>> wrong anywhere but write state. >>>> >>>> I just found the following in the spec (section 9.12): >>>> >>>> Thus, since the interface will allow a command transfer to be >>>> started or restarted >>>> at any time when the input buffer is empty, software could elect to >>>> simply retry >>>> the command upon detecting an error condition, or issue a ‘known >>>> good’ >>>> command in order to clear ERROR_STATE >>>> >>>> So a WRITE_START anywhere is ok. A WRITE_END in the wrong state >>>> should probably >>>> still go to error state. This means the user needs to be able to >>>> handle a write error at >>>> any time. It also means it's very important to make sure the user >>>> does a read before >>>> doing a write. If the host re-issues a WRITE_START and writes a >>>> new command >>>> between the time the use reads the data and writes the response, >>>> the response would >>>> be for the wrong command. >>>> >>>>>>> + switch (cmd) { >>>>>>> + case KCS_CMD_WRITE_START: >>>>>>> + kcs_bmc->data_in_avail = false; >>>>>>> + kcs_bmc->data_in_idx = 0; >>>>>>> + kcs_bmc->phase = KCS_PHASE_WRITE; >>>>>>> + kcs_bmc->error = KCS_NO_ERROR; >>>>>>> + break; >>>>>>> + >>>>>>> + case KCS_CMD_WRITE_END: >>>>>>> + kcs_bmc->phase = KCS_PHASE_WRITE_END; >>>>>>> + break; >>>>>>> + >>>>>>> + case KCS_CMD_ABORT: >>>>>>> + if (kcs_bmc->error == KCS_NO_ERROR) >>>>>>> + kcs_bmc->error = KCS_ABORTED_BY_COMMAND; >>>>>>> + >>>>>>> + kcs_bmc->phase = KCS_PHASE_ABORT_ERROR1; >>>>>>> + break; >>>>>>> + >>>>>>> + default: >>>>>>> + kcs_bmc->error = KCS_ILLEGAL_CONTROL_CODE; >>>>>>> + set_state(kcs_bmc, ERROR_STATE); >>>>>>> + write_data(kcs_bmc, kcs_bmc->error); >>>>>>> + kcs_bmc->phase = KCS_PHASE_ERROR; >>>>>>> + break; >>>>>>> + } >>>>>>> +} >>>>>>> + >>>>>>> +int kcs_bmc_handle_event(struct kcs_bmc *kcs_bmc) >>>>>>> +{ >>>>>>> + unsigned long flags; >>>>>>> + int ret = 0; >>>>>>> + u8 status; >>>>>>> + >>>>>>> + spin_lock_irqsave(&kcs_bmc->lock, flags); >>>>>>> + >>>>>>> + status = read_status(kcs_bmc) & (KCS_STATUS_IBF | >>>>>>> KCS_STATUS_CMD_DAT); >>>>>>> + >>>>>>> + switch (status) { >>>>>>> + case KCS_STATUS_IBF | KCS_STATUS_CMD_DAT: >>>>>>> + kcs_bmc_handle_command(kcs_bmc); >>>>>>> + break; >>>>>>> + >>>>>>> + case KCS_STATUS_IBF: >>>>>>> + kcs_bmc_handle_data(kcs_bmc); >>>>>>> + break; >>>>>>> + >>>>>>> + default: >>>>>>> + ret = -1; >>>>>>> + break; >>>>>>> + } >>>>>>> + >>>>>>> + spin_unlock_irqrestore(&kcs_bmc->lock, flags); >>>>>>> + >>>>>>> + return ret; >>>>>>> +} >>>>>>> +EXPORT_SYMBOL(kcs_bmc_handle_event); >>>>>>> + >>>>>>> +static inline struct kcs_bmc *file_kcs_bmc(struct file *filp) >>>>>>> +{ >>>>>>> + return container_of(filp->private_data, struct kcs_bmc, >>>>>>> miscdev); >>>>>>> +} >>>>>>> + >>>>>>> +static int kcs_bmc_open(struct inode *inode, struct file *filp) >>>>>>> +{ >>>>>>> + struct kcs_bmc *kcs_bmc = file_kcs_bmc(filp); >>>>>>> + int ret = 0; >>>>>>> + >>>>>>> + spin_lock_irq(&kcs_bmc->lock); >>>>>>> + >>>>>>> + if (!kcs_bmc->running) { >>>>>>> + kcs_bmc->running = 1; >>>>>>> + kcs_bmc->phase = KCS_PHASE_IDLE; >>>>>>> + kcs_bmc->data_in_avail = false; >>>>>> >>>>>> If you do everything right, setting the phase and data_in_avail >>>>>> should not >>>>>> be necessary here. >>>>>> >>>>>>> + } else { >>>>>>> + ret = -EBUSY; >>>>>>> + } >>>>>>> + >>>>>>> + spin_unlock_irq(&kcs_bmc->lock); >>>>>>> + >>>>>>> + return ret; >>>>>>> +} >>>>>>> + >>>>>>> +static unsigned int kcs_bmc_poll(struct file *filp, poll_table >>>>>>> *wait) >>>>>>> +{ >>>>>>> + struct kcs_bmc *kcs_bmc = file_kcs_bmc(filp); >>>>>>> + unsigned int mask = 0; >>>>>>> + >>>>>>> + poll_wait(filp, &kcs_bmc->queue, wait); >>>>>>> + >>>>>>> + spin_lock_irq(&kcs_bmc->lock); >>>>>>> + >>>>>>> + if (kcs_bmc->data_in_avail) >>>>>>> + mask |= POLLIN; >>>>>>> + >>>>>>> + spin_unlock_irq(&kcs_bmc->lock); >>>>>>> + >>>>>>> + return mask; >>>>>>> +} >>>>>>> + >>>>>>> +static ssize_t kcs_bmc_read(struct file *filp, char *buf, >>>>>>> + size_t count, loff_t *offset) >>>>>>> +{ >>>>>>> + struct kcs_bmc *kcs_bmc = file_kcs_bmc(filp); >>>>>>> + ssize_t ret = -EAGAIN; >>>>>>> + >>>>>> >>>>>> This function still has some issues. >>>>>> >>>>>> You can't call copy_to_user() with a spinlock held or interrupts >>>>>> disabled. >>>>>> To handle readers, you probably need a separate mutex. >>>>>> >>>>>> Also, this function can return -EAGAIN even if O_NONBLOCK is not >>>>>> set if >>>>>> kcs_bmc->data_in_avail changes between when you wait on the event >>>>>> and when you check it under the lock. >>>>>> >>>>>> You also clear data_in_avail even if the copy_to_user() fails, >>>>>> which is >>>>>> wrong. >>>>>> >>>>>> I believe the best way to handle this would be to have the spinlock >>>>>> protect the inner workings of the state machine and a mutex handle >>>>>> copying data out, setting/clearing the running flag (thus a mutex >>>>>> instead of spinlock in open and release) and the ioctl settings >>>>>> (except >>>>>> for abort where you will need to grab the spinlock). >>>>>> >>>>>> After the wait event below, grab the mutex. If data is not >>>>>> available >>>>>> and O_NONBLOCK is not set, drop the mutex and retry. Otherwise >>>>>> this is the only place (besides release) that sets data_in_avail >>>>>> to false. >>>>>> Do the copy_to_user(), grab the spinlock, clear data_in_avail and >>>>>> data_in_idx, then release the lock and mutex. If you are really >>>>>> adventurous you can do this without grabbing the lock using >>>>>> barriers, but it's probably not necessary here. >>>>>> >>>> >>>> With the state machine being able to be restarted at any time, you >>>> need >>>> something a little different here. You still need the mutex to handle >>>> multiple readers and the copy. I think the function should be >>>> something >>>> like: >>>> >>> Since KCS is not a multi-reader protocol from BMC's view, you makes >>> things complex. :-) >> >> No, I don't think you understand. The primary purpose of the complexity >> here is to protect the driver from the host system (on the other side of >> the KCS interface). Without this protection, it is possible for the >> host >> system to start a new write while the user on the BMC side is reading >> data out, resulting in corrupt data being read. >> >> I haven't thought too much about this. There may be a simpler way, >> but the protection needs to be there. >> >> And you may not think you need to protect the driver against a >> malicious BMC side user code, but you would be wrong. You can >> only have one opener, but with threads or a fork you can have >> multiple readers. And you don't know if a malicious piece of >> code has taken over userland. You always need to protect the >> kernel. >> > Sure, the read/write have protected the critical data area with IRQ, > and also, these > functions should be thread local safe I believe. > > spin_lock_irq(&kcs_bmc->lock); > ... > spin_unlock_irq(&kcs_bmc->lock); >
But remember, you can't call copy_to_user() when IRQs are off or when you are holding a spinlock. That is an absolute no. It can crash the kernel.
So you need a design that takes this into account, but will not result in the possibility of bad data being read.
>>>> static ssize_t kcs_bmc_read(struct file *filp, char *buf, >>>> size_t count, loff_t *offset) >>>> { >>>> struct kcs_bmc *kcs_bmc = file_kcs_bmc(filp); >>>> ssize_t ret; >>>> bool avail; >>>> size_t data_size; >>>> u8 *data; >>>> >>>> data = kmalloc(KCS_MSG_BUFSIZ, GFP_KERNEL); >>>> if (!data) >>>> return -ENOMEM; >>>> >>>> retry: >>>> ret = -EAGAIN; >>>> if (!(filp->f_flags & O_NONBLOCK)) >>>> wait_event_interruptible(kcs_bmc->queue, >>>> kcs_bmc->data_in_avail); >>>> >>>> mutex_lock(&kcs_bmc->read_mutex); >>>> >>>> spin_lock_irq(&kcs_bmc->lock); >>>> avail = kcs_bmc->data_in_avail; >>>> if (avail) { >>>> memcpy(data, kcs_bmc->data_in, kcs_bmc->data_in_idx); >>>> data_size = kcs_bmc->data_in_idx; >>>> } >>>> spin_unlock_irq(&kcs_bmc->lock); >>>> >>>> if (!avail) { >>>> if (filp->f_flags & O_NONBLOCK) >>>> goto out_mutex_unlock; >>>> mutex_unlock(&kcs_bmc->read_mutex); >>>> goto retry; >>>> } >>>> >>>> if (count < data_size) { >>>> ret = -EOVERFLOW; >>>> ? I'm not sure about the error, but userspace needs to >>>> know. >>>> goto out_mutex_unlock; >> >> Maybe a length error to the host side here?
You didn't comment on this or the other length error. That needs to be handled.
>> >>>> } >>>> >>>> if (!copy_to_user(buf, data, data_size)) { >>>> ret = -EFAULT; >>>> goto out_mutex_unlock; >>>> } >>>> >>>> ret = data_size; >>>> >>>> spin_lock_irq(&kcs_bmc->lock); >>>> >>>> if (kcs_bmc->phase != KCS_PHASE_WRITE_END_DONE) >>>> /* Something aborted or restarted the state machine. */ >>>> ? Maybe restart if O_NONBLOCK is not set and -EAGAIN if >>>> it is? >>>> ret = -EIO; >>>> } else { >>>> kcs_bmc->phase = KCS_PHASE_WAIT_READ; >>>> kcs_bmc->data_in_avail = false; >>>> kcs_bmc->data_in_idx = 0; >>>> } >>>> >>>> spin_unlock_irq(&kcs_bmc->lock); >>>> >>>> out_mutex_unlock: >>>> mutex_unlock(&kcs_bmc->read_mutex); >>>> >>>> kfree(data); >>>> >>>> return ret; >>>> } >>>> Note that I added a state, KCS_PHASE_WRITE_END_DONE, which would be >>>> set after the final byte from the host is received. You want the >>>> read here >>>> done before you can do the write below to avoid the race I talked >>>> about. >>>> >>>> There is a local copy made of the data. What you *never* want to >>>> happen >>>> here is for the state machine to start processing a new write command >>>> while the data is being copied. It could result in corrupt data >>>> being read >>>> and some random operation being done by the BMC. >>>> >>>> If you want to avoid the local copy, it could be done, but it's >>>> more complex. >>>> >>>>>>> + if (!(filp->f_flags & O_NONBLOCK)) >>>>>>> + wait_event_interruptible(kcs_bmc->queue, >>>>>>> + kcs_bmc->data_in_avail); >>>>>>> + >>>>>>> + spin_lock_irq(&kcs_bmc->lock); >>>>>>> + >>>>>>> + if (kcs_bmc->data_in_avail) { >>>>>>> + kcs_bmc->data_in_avail = false; >>>>>>> + >>>>>>> + if (count > kcs_bmc->data_in_idx) >>>>>>> + count = kcs_bmc->data_in_idx; >>>>>>> + >>>>>>> + if (!copy_to_user(buf, kcs_bmc->data_in, count)) >>>>>>> + ret = count; >>>>>>> + else >>>>>>> + ret = -EFAULT; >>>>>>> + } >>>>>>> + >>>>>>> + spin_unlock_irq(&kcs_bmc->lock); >>>>>>> + >>>>>>> + return ret; >>>>>>> +} >>>>>>> + >>>>>>> +static ssize_t kcs_bmc_write(struct file *filp, const char *buf, >>>>>>> + size_t count, loff_t *offset) >>>>>>> +{ >>>>>>> + struct kcs_bmc *kcs_bmc = file_kcs_bmc(filp); >>>>>>> + ssize_t ret = count; >>>>>>> + >>>>>>> + if (count < 1 || count > KCS_MSG_BUFSIZ) >>>>>>> + return -EINVAL; >>>>>>> + >>>>>>> + spin_lock_irq(&kcs_bmc->lock); >>>>>>> + >>>>>>> + if (kcs_bmc->phase == KCS_PHASE_WAIT_READ) { >>>>>>> + if (copy_from_user(kcs_bmc->data_out, buf, count)) { >>>>>>> + spin_unlock_irq(&kcs_bmc->lock); >>>>>>> + return -EFAULT; >>>>>>> + } >>>>>>> + >>>>>>> + kcs_bmc->phase = KCS_PHASE_READ; >>>>>>> + kcs_bmc->data_out_idx = 1; >>>>>>> + kcs_bmc->data_out_len = count; >>>>>>> + write_data(kcs_bmc, kcs_bmc->data_out[0]); >>>>>>> + } else if (kcs_bmc->phase == KCS_PHASE_READ) { >>>>>>> + ret = -EBUSY; >>>>>>> + } else { >>>>>>> + ret = -EINVAL; >>>>>> >>>>>> Is there a reason you return -EINVAL here? Why not just -EBUSY >>>>>> in all >>>>>> cases? Is there something that userland will need to do >>>>>> differently? >>>>>> >>>>>>> + } >>>>>>> + >>>>>>> + spin_unlock_irq(&kcs_bmc->lock); >>>>>>> + >>>>>>> + return ret; >>>>>>> +} >>>>>>> + >>>>>>> +static long kcs_bmc_ioctl(struct file *filp, unsigned int cmd, >>>>>>> + unsigned long arg) >>>>>>> +{ >>>>>>> + struct kcs_bmc *kcs_bmc = file_kcs_bmc(filp); >>>>>>> + long ret = 0; >>>>>>> + >>>>>>> + spin_lock_irq(&kcs_bmc->lock); >>>>>>> + >>>>>>> + switch (cmd) { >>>>>>> + case IPMI_BMC_IOCTL_SET_SMS_ATN: >>>>>>> + update_status_bits(kcs_bmc, KCS_STATUS_SMS_ATN, >>>>>>> + KCS_STATUS_SMS_ATN); >>>>>>> + break; >>>>>>> + >>>>>>> + case IPMI_BMC_IOCTL_CLEAR_SMS_ATN: >>>>>>> + update_status_bits(kcs_bmc, KCS_STATUS_SMS_ATN, >>>>>>> + 0); >>>>>>> + break; >>>>>>> + >>>>>>> + case IPMI_BMC_IOCTL_FORCE_ABORT: >>>>>>> + set_state(kcs_bmc, ERROR_STATE); >>>>>>> + read_data(kcs_bmc); >>>>>>> + write_data(kcs_bmc, KCS_ZERO_DATA); >>>>>>> + >>>>>>> + kcs_bmc->phase = KCS_PHASE_ERROR; >>>>>>> + kcs_bmc->data_in_avail = false; >>>>>>> + break; >>>>>>> + >>>>>>> + default: >>>>>>> + ret = -EINVAL; >>>>>>> + break; >>>>>>> + } >>>>>>> + >>>>>>> + spin_unlock_irq(&kcs_bmc->lock); >>>>>>> + >>>>>>> + return ret; >>>>>>> +} >>>>>>> + >>>>>>> +static int kcs_bmc_release(struct inode *inode, struct file *filp) >>>>>>> +{ >>>>>>> + struct kcs_bmc *kcs_bmc = file_kcs_bmc(filp); >>>>>>> + >>>>>> >>>>>> What happens if the device gets closed in the middle of a >>>>>> transaction? That's >>>>>> an important case to handle. If something is in process, you >>>>>> need to abort it. >>>>>> >>>>> The device just provides the read & write data, the transaction is >>>>> handled in the KCS >>>>> controller's IRQ handler. >>>> >>>> From the spec, section 9.14: >>>> >>>> The BMC must change the status to ERROR_STATE on any condition >>>> where it >>>> aborts a command transfer in progress. >>>> >>>> So you need to do something here. >>>> >>> In practice, we do this as spec said in ipmid, NOT in driver, driver >>> can't handle anything, let's >>> make it simple, thanks! >> >> If ipmid crashes or is killed, how does it accomplish this? >> > Every time ipmids (or kcsd) crashed or killed, it needs start to call > FORCE_ARBORT firstly, to sync with > host side software. >>> >>> Whenever the BMC is reset (from power-on or a hard reset), the State >>> Bits are initialized to “11 - Error State”. Doing so >>> allows SMS to detect that the BMC has been reset and that any >>> message in process has been terminated by the BMC. >> >> Right, that's fine, like it should be. But we are not talking about >> a reset. >> > I think the final error handling solution is that kcsd (user land) > runs, otherwise, the host software side still got stuck. We meet > this kind of issue, so in general, we just doesn't handle some mirror > errors in driver, then in kcsd, when it can provide the real > IPMI service, it will reset the channel firstly to sync with host side > software.
"Userland will do the right thing" is not very convincing to a kernel developer.
Plus if the above is true, I would think that you would just want to hold the device in an error state when it wasn't opened.
-corey
>> -corey >> >>>>>>> + spin_lock_irq(&kcs_bmc->lock); >>>>>>> + >>>>>>> + kcs_bmc->running = 0; >>>>>>> + >>>>>>> + spin_unlock_irq(&kcs_bmc->lock); >>>>>>> + >>>>>>> + return 0; >>>>>>> +} >>>>>>> + >>>> >>>> >>> >> >
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