dmaengine: idxd: handle interrupt handle revoked event

"Interrupt handle revoked" is an event that happens when the driver is
running on a guest kernel and the VM is migrated to a new machine.
The device will trigger an interrupt that signals to the guest driver
that the interrupt handles need to be replaced.

The misc irq thread function calls a helper function to handle the
event. The function uses the WQ percpu_ref to quiesce the kernel
submissions. It then replaces the interrupt handles by requesting
interrupt handle command for each I/O MSIX vector. Once the handle is
updated, the driver will unblock the submission path to allow new
submissions.

The submitter will attempt to acquire a percpu_ref before submission. When
the request fails, it will wait on the wq_resurrect 'completion'.

The driver does anticipate the possibility of descriptors being submitted
before the WQ percpu_ref is killed. If a descriptor has already been
submitted, it will return with incorrect interrupt handle status. The
descriptor will be re-submitted with the new interrupt handle on the
completion path. For descriptors with incorrect interrupt handles,
completion interrupt won't be triggered.

At the completion of the interrupt handle refresh, the handling function
will call idxd_int_handle_refresh_drain() to issue drain descriptors to
each of the wq with associated interrupt handle. The drain descriptor will have
interrupt request set but without completion record. This will ensure all
descriptors with incorrect interrupt completion handle get drained and
a completion interrupt is triggered for the guest driver to process them.

Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Co-Developed-by: Sanjay Kumar <sanjay.k.kumar@intel.com>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Link: https://lore.kernel.org/r/163528420189.3925689.18212568593220415551.stgit@djiang5-desk3.ch.intel.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>

1 files changed, 5 insertions, 1 deletions

diff --git a/drivers/dma/idxd/device.c b/drivers/dma/idxd/device.c
index 943e9967627b..1dc5245107df 100644
--- a/drivers/dma/idxd/device.c
+++ b/drivers/dma/idxd/device.c
@@ -404,17 +404,21 @@ int idxd_wq_init_percpu_ref(struct idxd_wq *wq)
 	int rc;
 
 	memset(&wq->wq_active, 0, sizeof(wq->wq_active));
-	rc = percpu_ref_init(&wq->wq_active, idxd_wq_ref_release, 0, GFP_KERNEL);
+	rc = percpu_ref_init(&wq->wq_active, idxd_wq_ref_release,
+			     PERCPU_REF_ALLOW_REINIT, GFP_KERNEL);
 	if (rc < 0)
 		return rc;
 	reinit_completion(&wq->wq_dead);
+	reinit_completion(&wq->wq_resurrect);
 	return 0;
 }
 
 void __idxd_wq_quiesce(struct idxd_wq *wq)
 {
 	lockdep_assert_held(&wq->wq_lock);
+	reinit_completion(&wq->wq_resurrect);
 	percpu_ref_kill(&wq->wq_active);
+	complete_all(&wq->wq_resurrect);
 	wait_for_completion(&wq->wq_dead);
 }