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

Vinod Koul
2020-10-05T04:42:19Z

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 ;)

> +
> 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

--
~Vinod