Messages in this thread | | | Subject | Re: [PATCH arm/aspeed/ast2500 v2] ipmi: add an Aspeed KCS IPMI BMC driver | From | "Wang, Haiyue" <> | Date | Wed, 31 Jan 2018 09:37:58 +0800 |
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On 2018-01-31 09:25, Corey Minyard wrote: > On 01/30/2018 07:02 PM, Wang, Haiyue wrote: >> >> >> On 2018-01-31 08:52, Corey Minyard wrote: >>> 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. >>> >> Yes, sure, as I said before: access_ok(VERIFY_WRITE, to, n), then >> memcpy in spin_lock. > > Where did you get the idea that this was ok? It's not. access_ok() is > not actually very > useful, since the permissions on memory can change at any time unless > you are holding > the mm lock, which is also not an ok thing to do. It is entirely > possible for access_ok() > to pass and copy_to_user() to fail. > I thought memcpy will not fail. :( > I'm not exactly sure what you are saying, though. In any event, a > well-designed read()/write() > operation should leave the system unchanged if it gets an error. > I saw BT use a local buffer, If I change the '#define KCS_MSG_BUFSIZ 1024' to ".. 512", should it be OK as BT ?
static ssize_t bt_bmc_read(struct file *file, char __user *buf, size_t count, loff_t *ppos) { struct bt_bmc *bt_bmc = file_bt_bmc(file); u8 len; int len_byte = 1; u8 kbuffer[BT_BMC_BUFFER_SIZE]; --> #define BT_BMC_BUFFER_SIZE 256
> -corey > >>>>>>> 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. >>> >> Yes, will send a length error by following KCS spec. >>>>> >>>>>>> } >>>>>>> >>>>>>> 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. >>> >> I understand your concern, of course, driver need handles things >> well. But in fact, if a user app is truly a bad boy, it still can hang >> the host side: set SMS_ATN, but no message returned when software >> host side requests, then host open-ipmi driver will hang, we >> meet this kind of error to hang the customer's host. :) In my >> understanding, kcs-bmc should do the right thing about read and write, >> the real transaction should be handled correctly by the kcsd. >> >> And if no kcsd starts, then this kind of BMC can't be sold out. :) > > True. I'm not as concerned about this sort of thing. It's nicer to > the host side if > it can detect problems quickly, but it will eventually time out. > > From what I can tell from the current design, if the BMC userland is > not running, > the driver will step through the state machine until it hits read > state, then it > will sit there until the host times out and aborts the operation. > > IMHO, it would be better for the host side if the driver just stayed > in error state > if nothing had it open. It would think the spec says that in the > quote I referenced > above, but that quote, like many things in the IPMI spec, is fairly > vague and could > be interpreted many ways. > Well, I will try to fix this errors as possible. > -corey > > >>> -corey >>> >>>>> -corey >>>>> >>>>>>>>>> + spin_lock_irq(&kcs_bmc->lock); >>>>>>>>>> + >>>>>>>>>> + kcs_bmc->running = 0; >>>>>>>>>> + >>>>>>>>>> + spin_unlock_irq(&kcs_bmc->lock); >>>>>>>>>> + >>>>>>>>>> + return 0; >>>>>>>>>> +} >>>>>>>>>> + >>>>>>> >>>>>>> >>>>>> >>>>> >>>> >>> >> >
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