Messages in this thread | | | Subject | Re: [PATCH v4 2/7] s390: ap: new vfio_ap_queue structure | From | Pierre Morel <> | Date | Wed, 27 Feb 2019 09:40:12 +0100 |
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On 26/02/2019 17:10, Tony Krowiak wrote: > On 2/22/19 10:29 AM, Pierre Morel wrote: >> The AP interruptions are assigned on a queue basis and >> the GISA structure is handled on a VM basis, so that >> we need to add a structure we can retrieve from both side >> holding the information we need to handle PQAP/AQIC interception >> and setup the GISA. >> >> Since we can not add more information to the ap_device >> we add a new structure vfio_ap_queue, to hold per queue >> information useful to handle interruptions and set it as >> driver's data of the standard ap_queue device. >> >> Usually, the device and the mediated device are linked together >> but in the vfio_ap driver design we have a bunch of "sub" devices >> (the ap_queue devices) belonging to the mediated device. >> >> Linking these structure to the mediated device it is assigned to, >> with the help of the vfio_ap_queue structure will help us to >> retrieve the AP devices associated with the mediated devices >> during the mediated device operations. >> >> ------------ ------------- >> | AP queue |--> | AP_vfio_q |<---- >> ------------ ------^------ | --------------- >> | <--->| matrix_mdev | >> ------------ ------v------ | --------------- >> | AP queue |--> | AP_vfio_q |----- >> ------------ ------------- >> >> The vfio_ap_queue device will hold the following entries: >> - apqn: AP queue number (defined here) >> - isc : Interrupt subclass (defined later) >> - nib : notification information byte (defined later) >> - list: a list_head entry allowing to link this structure to a >> matrix mediated device it is assigned to. >> >> The vfio_ap_queue structure is allocated when the vfio_ap_driver >> is probed and added as driver data to the ap_queue device. >> It is free on remove. >> >> The structure is linked to the matrix_dev host device at the >> probe of the device building some kind of free list for the >> matrix mediated devices. >> >> When the vfio_queue is associated to a matrix mediated device, >> the vfio_ap_queue device is linked to this matrix mediated device >> and unlinked when dissociated. >> >> This patch and the 3 next can be squashed together on the >> final release of this series. >> until then I separate them to ease the review. >> >> So please do not complain about unused functions or about >> squashing the patches together, this will be resolved during >> the last iteration. >> >> Signed-off-by: Pierre Morel <pmorel@linux.ibm.com> >> --- >> drivers/s390/crypto/vfio_ap_drv.c | 27 ++++++++++++++++++++++++++- >> drivers/s390/crypto/vfio_ap_private.h | 9 +++++++++ >> 2 files changed, 35 insertions(+), 1 deletion(-) >> >> diff --git a/drivers/s390/crypto/vfio_ap_drv.c >> b/drivers/s390/crypto/vfio_ap_drv.c >> index e9824c3..eca0ffc 100644 >> --- a/drivers/s390/crypto/vfio_ap_drv.c >> +++ b/drivers/s390/crypto/vfio_ap_drv.c >> @@ -40,14 +40,38 @@ static struct ap_device_id ap_queue_ids[] = { >> MODULE_DEVICE_TABLE(vfio_ap, ap_queue_ids); >> +/** >> + * vfio_ap_queue_dev_probe: >> + * >> + * Allocate a vfio_ap_queue structure and associate it >> + * with the device as driver_data. >> + */ >> static int vfio_ap_queue_dev_probe(struct ap_device *apdev) >> { >> + struct vfio_ap_queue *q; >> + >> + q = kzalloc(sizeof(*q), GFP_KERNEL); >> + if (!q) >> + return -ENOMEM; >> + dev_set_drvdata(&apdev->device, q); >> + q->apqn = to_ap_queue(&apdev->device)->qid; >> + INIT_LIST_HEAD(&q->list); >> + list_add(&q->list, &matrix_dev->free_list); >> return 0; >> } >> +/** >> + * vfio_ap_queue_dev_remove: >> + * >> + * Free the associated vfio_ap_queue structure >> + */ >> static void vfio_ap_queue_dev_remove(struct ap_device *apdev) >> { >> - /* Nothing to do yet */ >> + struct vfio_ap_queue *q; >> + >> + q = dev_get_drvdata(&apdev->device); >> + list_del(&q->list); >> + kfree(q); >> } >> static void vfio_ap_matrix_dev_release(struct device *dev) >> @@ -107,6 +131,7 @@ static int vfio_ap_matrix_dev_create(void) >> matrix_dev->device.bus = &matrix_bus; >> matrix_dev->device.release = vfio_ap_matrix_dev_release; >> matrix_dev->vfio_ap_drv = &vfio_ap_drv; >> + INIT_LIST_HEAD(&matrix_dev->free_list); >> ret = device_register(&matrix_dev->device); >> if (ret) >> diff --git a/drivers/s390/crypto/vfio_ap_private.h >> b/drivers/s390/crypto/vfio_ap_private.h >> index 76b7f98..2760178 100644 >> --- a/drivers/s390/crypto/vfio_ap_private.h >> +++ b/drivers/s390/crypto/vfio_ap_private.h >> @@ -39,6 +39,7 @@ struct ap_matrix_dev { >> atomic_t available_instances; >> struct ap_config_info info; >> struct list_head mdev_list; >> + struct list_head free_list; >> struct mutex lock; >> struct ap_driver *vfio_ap_drv; >> }; >> @@ -81,9 +82,17 @@ struct ap_matrix_mdev { >> struct ap_matrix matrix; >> struct notifier_block group_notifier; >> struct kvm *kvm; >> + struct list_head qlist; > > I do not see much value in maintaining two lists of at the > expense of complicating the code and introducing additional > processing (i.e., list rewinds etc.). IMHO, the only think it buys > us is being able to pass a smaller list to the vfio_ap_get_queue() > function to traverse. That function can traverse the list in > struct ap_matrix_dev to find a queue. I understand what you are > doing here in pulling vfio_ap_queue structs from the free_list > to add them to qlist for the mdev when adapter/domain assignment > takes place, but you are now maintaining links to the vfio_ap_queue > in multiple places; as drvdata as well as two lists. I think this > is over designing.
This is not completely exact, the drvdata allows to retrieve the vfio_ap_queue structure from the AP device, which is global to all AP devices, and not related to a mediated device.
The vfio_ap_queue structure is only linked to one of the different lists it can be linked to: the free_list or the mediated device list.
The complication of the code you mention make us win almost 200 LOCs, some may see it as a simplification ;) .
Regards, Pierre
-- Pierre Morel Linux/KVM/QEMU in Böblingen - Germany
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