Re: [PATCH v6 4/5] dmaengine: idxd: Clean up descriptors with fault error

Dave Jiang
2020-10-05T04:55:51Z

On 10/4/2020 9:42 PM, Vinod Koul wrote:
> On 24-09-20, 11:00, Dave Jiang wrote:
>> Add code to "complete" a descriptor when the descriptor or its completion
>> address hit a fault error when SVA mode is being used. This error can be
>> triggered due to bad programming by the user. A lock is introduced in order
>> to protect the descriptor completion lists since the fault handler will run
>> from the system work queue after being scheduled in the interrupt handler.
>>
>> Signed-off-by: Dave Jiang <dave.jiang@intel.com>
>> Reviewed-by: Tony Luck <tony.luck@intel.com>
>> Reviewed-by: Dan Williams <dan.j.williams@intel.com>
>> ---
>> drivers/dma/idxd/idxd.h | 5 ++
>> drivers/dma/idxd/init.c | 1 +
>> drivers/dma/idxd/irq.c | 143 ++++++++++++++++++++++++++++++++++++----
>> 3 files changed, 137 insertions(+), 12 deletions(-)
>>
>> diff --git a/drivers/dma/idxd/idxd.h b/drivers/dma/idxd/idxd.h
>> index 43a216c42d25..b64b6266ca97 100644
>> --- a/drivers/dma/idxd/idxd.h
>> +++ b/drivers/dma/idxd/idxd.h
>> @@ -34,6 +34,11 @@ struct idxd_irq_entry {
>> int id;
>> struct llist_head pending_llist;
>> struct list_head work_list;
>> + /*
>> + * Lock to protect access between irq thread process descriptor
>> + * and irq thread processing error descriptor.
>> + */
>> + spinlock_t list_lock;
>> };
>>
>> struct idxd_group {
>> diff --git a/drivers/dma/idxd/init.c b/drivers/dma/idxd/init.c
>> index 626401a71fdd..1bb7637b02eb 100644
>> --- a/drivers/dma/idxd/init.c
>> +++ b/drivers/dma/idxd/init.c
>> @@ -97,6 +97,7 @@ static int idxd_setup_interrupts(struct idxd_device *idxd)
>> for (i = 0; i < msixcnt; i++) {
>> idxd->irq_entries[i].id = i;
>> idxd->irq_entries[i].idxd = idxd;
>> + spin_lock_init(&idxd->irq_entries[i].list_lock);
>> }
>>
>> msix = &idxd->msix_entries[0];
>> diff --git a/drivers/dma/idxd/irq.c b/drivers/dma/idxd/irq.c
>> index 17a65a13fb64..9e6cc55ad22f 100644
>> --- a/drivers/dma/idxd/irq.c
>> +++ b/drivers/dma/idxd/irq.c
>> @@ -11,6 +11,24 @@
>> #include "idxd.h"
>> #include "registers.h"
>>
>> +enum irq_work_type {
>> + IRQ_WORK_NORMAL = 0,
>> + IRQ_WORK_PROCESS_FAULT,
>> +};
>> +
>> +struct idxd_fault {
>> + struct work_struct work;
>> + u64 addr;
>> + struct idxd_device *idxd;
>> +};
>> +
>> +static int irq_process_work_list(struct idxd_irq_entry *irq_entry,
>> + enum irq_work_type wtype,
>> + int *processed, u64 data);
>> +static int irq_process_pending_llist(struct idxd_irq_entry *irq_entry,
>> + enum irq_work_type wtype,
>> + int *processed, u64 data);
>> +
>> static void idxd_device_reinit(struct work_struct *work)
>> {
>> struct idxd_device *idxd = container_of(work, struct idxd_device, work);
>> @@ -44,6 +62,46 @@ static void idxd_device_reinit(struct work_struct *work)
>> idxd_device_wqs_clear_state(idxd);
>> }
>>
>> +static void idxd_device_fault_work(struct work_struct *work)
>> +{
>> + struct idxd_fault *fault = container_of(work, struct idxd_fault, work);
>> + struct idxd_irq_entry *ie;
>> + int i;
>> + int processed;
>> + int irqcnt = fault->idxd->num_wq_irqs + 1;
>> +
>> + for (i = 1; i < irqcnt; i++) {
>> + ie = &fault->idxd->irq_entries[i];
>> + irq_process_work_list(ie, IRQ_WORK_PROCESS_FAULT,
>> + &processed, fault->addr);
>> + if (processed)
>> + break;
>> +
>> + irq_process_pending_llist(ie, IRQ_WORK_PROCESS_FAULT,
>> + &processed, fault->addr);
>> + if (processed)
>> + break;
>> + }
>> +
>> + kfree(fault);
>> +}
>> +
>> +static int idxd_device_schedule_fault_process(struct idxd_device *idxd,
>> + u64 fault_addr)
>> +{
>> + struct idxd_fault *fault;
>> +
>> + fault = kmalloc(sizeof(*fault), GFP_ATOMIC);
>> + if (!fault)
>> + return -ENOMEM;
>> +
>> + fault->addr = fault_addr;
>> + fault->idxd = idxd;
>> + INIT_WORK(&fault->work, idxd_device_fault_work);
>> + queue_work(idxd->wq, &fault->work);
>> + return 0;
>> +}
>> +
>> irqreturn_t idxd_irq_handler(int vec, void *data)
>> {
>> struct idxd_irq_entry *irq_entry = data;
>> @@ -125,6 +183,16 @@ irqreturn_t idxd_misc_thread(int vec, void *data)
>> if (!err)
>> goto out;
>>
>> + /*
>> + * This case should rarely happen and typically is due to software
>> + * programming error by the driver.
>> + */
>> + if (idxd->sw_err.valid &&
>> + idxd->sw_err.desc_valid &&
>> + idxd->sw_err.fault_addr)
>> + idxd_device_schedule_fault_process(idxd,
>> + idxd->sw_err.fault_addr);
>
> This should fit in a single line ;)

Yes. With the new 100 col guideline this should be single line.

>
>> +
>> gensts.bits = ioread32(idxd->reg_base + IDXD_GENSTATS_OFFSET);
>> if (gensts.state == IDXD_DEVICE_STATE_HALT) {
>> idxd->state = IDXD_DEV_HALTED;
>> @@ -152,57 +220,106 @@ irqreturn_t idxd_misc_thread(int vec, void *data)
>> return IRQ_HANDLED;
>> }
>>
>> +static bool process_fault(struct idxd_desc *desc, u64 fault_addr)
>> +{
>> + if ((u64)desc->hw == fault_addr ||
>> + (u64)desc->completion == fault_addr) {
>
> you are casting descriptor address and completion, I can understand
> former, but later..? Can you explain this please
>

It is possible to fail on the completion writeback address if the completion
address programmed into the descriptor is bad.