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Subject[PATCH 5.6 080/126] dmaengine: idxd: fix interrupt completion after unmasking
Date
From: Dave Jiang <dave.jiang@intel.com>

commit 4f302642b70c1348773fe7e3ded9fc315fa92990 upstream.

The current implementation may miss completions after we unmask the
interrupt. In order to make sure we process all competions, we need to:
1. Do an MMIO read from the device as a barrier to ensure that all PCI
writes for completions have arrived.
2. Check for any additional completions that we missed.

Fixes: 8f47d1a5e545 ("dmaengine: idxd: connect idxd to dmaengine subsystem")

Reported-by: Sanjay Kumar <sanjay.k.kumar@intel.com>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Link: https://lore.kernel.org/r/158834641769.35613.1341160109892008587.stgit@djiang5-desk3.ch.intel.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/dma/idxd/device.c | 7 +++++++
drivers/dma/idxd/irq.c | 26 +++++++++++++++++++-------
2 files changed, 26 insertions(+), 7 deletions(-)

--- a/drivers/dma/idxd/device.c
+++ b/drivers/dma/idxd/device.c
@@ -62,6 +62,13 @@ int idxd_unmask_msix_vector(struct idxd_
perm.ignore = 0;
iowrite32(perm.bits, idxd->reg_base + offset);

+ /*
+ * A readback from the device ensures that any previously generated
+ * completion record writes are visible to software based on PCI
+ * ordering rules.
+ */
+ perm.bits = ioread32(idxd->reg_base + offset);
+
return 0;
}

--- a/drivers/dma/idxd/irq.c
+++ b/drivers/dma/idxd/irq.c
@@ -173,6 +173,7 @@ static int irq_process_pending_llist(str
struct llist_node *head;
int queued = 0;

+ *processed = 0;
head = llist_del_all(&irq_entry->pending_llist);
if (!head)
return 0;
@@ -197,6 +198,7 @@ static int irq_process_work_list(struct
struct list_head *node, *next;
int queued = 0;

+ *processed = 0;
if (list_empty(&irq_entry->work_list))
return 0;

@@ -218,10 +220,9 @@ static int irq_process_work_list(struct
return queued;
}

-irqreturn_t idxd_wq_thread(int irq, void *data)
+static int idxd_desc_process(struct idxd_irq_entry *irq_entry)
{
- struct idxd_irq_entry *irq_entry = data;
- int rc, processed = 0, retry = 0;
+ int rc, processed, total = 0;

/*
* There are two lists we are processing. The pending_llist is where
@@ -244,15 +245,26 @@ irqreturn_t idxd_wq_thread(int irq, void
*/
do {
rc = irq_process_work_list(irq_entry, &processed);
- if (rc != 0) {
- retry++;
+ total += processed;
+ if (rc != 0)
continue;
- }

rc = irq_process_pending_llist(irq_entry, &processed);
- } while (rc != 0 && retry != 10);
+ total += processed;
+ } while (rc != 0);
+
+ return total;
+}
+
+irqreturn_t idxd_wq_thread(int irq, void *data)
+{
+ struct idxd_irq_entry *irq_entry = data;
+ int processed;

+ processed = idxd_desc_process(irq_entry);
idxd_unmask_msix_vector(irq_entry->idxd, irq_entry->id);
+ /* catch anything unprocessed after unmasking */
+ processed += idxd_desc_process(irq_entry);

if (processed == 0)
return IRQ_NONE;

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