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

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