Re: [PATCH v3 4/9] s390: ap: tools to find a queue with a specific APQN

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



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




[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[Index of Archives]     [Kernel Development]     [Kernel Newbies]     [IDE]     [Security]     [Git]     [Netfilter]     [Bugtraq]     [Yosemite Info]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux RAID]     [Linux ATA RAID]     [Samba]     [Linux Media]     [Device Mapper]

  Powered by Linux