On 18/02/2019 13:21, Cornelia Huck wrote:
On Fri, 15 Feb 2019 17:13:21 -0500
Tony Krowiak <akrowiak@xxxxxxxxxxxxx> wrote:
On 2/14/19 8:51 AM, Pierre Morel wrote:
We need to find the queue with a specific APQN during the
handling of the interception of the PQAP/AQIC instruction.
To handle the AP associated device reference count we keep
track of it in the vfio_ap_queue until we put the device.
Signed-off-by: Pierre Morel <pmorel@xxxxxxxxxxxxx>
---
drivers/s390/crypto/vfio_ap_ops.c | 54 +++++++++++++++++++++++++++++++++++
drivers/s390/crypto/vfio_ap_private.h | 1 +
2 files changed, 55 insertions(+)
+/**
+ * vfio_ap_get_queue: Retrieve a queue with a specific APQN
+ * @apqn: The queue APQN
+ *
+ * Retrieve a queue with a specific APQN from the list of the
+ * devices associated to the vfio_ap_driver.
+ *
+ * The vfio_ap_queue has been already associated with the device
+ * during the probe.
+ * Store the associated device for reference counting
+ *
+ * Returns the pointer to the associated vfio_ap_queue
+ */
+static __attribute__((unused))
+ struct vfio_ap_queue *vfio_ap_get_queue(int apqn)
I think you should change this signature for the reasons I stated
below:
struct device *vfio_ap_get_queue_dev(int apqn)
+{
+ struct device *dev;
+ struct vfio_ap_queue *q;
+
+ dev = driver_find_device(&matrix_dev->vfio_ap_drv->driver, NULL, &apqn,
+ vfio_ap_check_apqn);
+ if (!dev)
+ return NULL;
+ q = dev_get_drvdata(dev);
+ q->dev = dev;
Why store the device with the vfio_ap_queue object? Why not just return
the device. The caller can get the vfio_ap_queue from the device's
driver data. It seems the only reason for the 'dev' field is to
temporarily hold a ref to the device so it can be put later. Why not
just put the device.
Having looked at the remainder of the patches, I tend to agree that we
don't really need the backlink; we walk the driver's list of devices in
any case IIUC.
We *might* want a mechanism to grab the queue quickly (i.e. without
walking the list) if there's anything performance sensitive in there;
but from the patch descriptions, I don't think anything is done in a
hot path, so it should be fine.
OK you are right, I ll drop it
--
Pierre Morel
Linux/KVM/QEMU in Böblingen - Germany
