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This patch fixes a lockdep splat introduced by commitf21916ec48("s390/vfio-ap: clean up vfio_ap resources when KVM pointer invalidated"). The lockdep splat only occurs when starting a Secure Execution guest. Crypto virtualization (vfio_ap) is not yet supported for SE guests; however, in order to avoid this problem when support becomes available, this fix is being provided. The circular locking dependency was introduced when the setting of the masks in the guest's APCB was executed while holding the matrix_dev->lock. While the lock is definitely needed to protect the setting/unsetting of the matrix_mdev->kvm pointer, it is not necessarily critical for setting the masks; so, the matrix_dev->lock will be released while the masks are being set or cleared. Keep in mind, however, that another process that takes the matrix_dev->lock can get control while the masks in the guest's APCB are being set or cleared as a result of the driver being notified that the KVM pointer has been set or unset. This could result in invalid access to the matrix_mdev->kvm pointer by the intervening process. To avoid this scenario, two new fields are being added to the ap_matrix_mdev struct: struct ap_matrix_mdev { ... bool kvm_busy; wait_queue_head_t wait_for_kvm; ... }; The functions that handle notification that the KVM pointer value has been set or cleared will set the kvm_busy flag to true until they are done processing at which time they will set it to false and wake up the tasks on the matrix_mdev->wait_for_kvm wait queue. Functions that require access to matrix_mdev->kvm will sleep on the wait queue until they are awakened at which time they can safely access the matrix_mdev->kvm field. Fixes:f21916ec48("s390/vfio-ap: clean up vfio_ap resources when KVM pointer invalidated") Cc: stable@vger.kernel.org Signed-off-by: Tony Krowiak <akrowiak@linux.ibm.com> Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
107 lines
3.2 KiB
C
107 lines
3.2 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* Private data and functions for adjunct processor VFIO matrix driver.
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*
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* Author(s): Tony Krowiak <akrowiak@linux.ibm.com>
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* Halil Pasic <pasic@linux.ibm.com>
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* Pierre Morel <pmorel@linux.ibm.com>
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*
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* Copyright IBM Corp. 2018
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*/
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#ifndef _VFIO_AP_PRIVATE_H_
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#define _VFIO_AP_PRIVATE_H_
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#include <linux/types.h>
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#include <linux/device.h>
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#include <linux/mdev.h>
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#include <linux/delay.h>
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#include <linux/mutex.h>
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#include <linux/kvm_host.h>
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#include "ap_bus.h"
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#define VFIO_AP_MODULE_NAME "vfio_ap"
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#define VFIO_AP_DRV_NAME "vfio_ap"
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/**
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* ap_matrix_dev - the AP matrix device structure
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* @device: generic device structure associated with the AP matrix device
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* @available_instances: number of mediated matrix devices that can be created
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* @info: the struct containing the output from the PQAP(QCI) instruction
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* mdev_list: the list of mediated matrix devices created
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* lock: mutex for locking the AP matrix device. This lock will be
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* taken every time we fiddle with state managed by the vfio_ap
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* driver, be it using @mdev_list or writing the state of a
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* single ap_matrix_mdev device. It's quite coarse but we don't
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* expect much contention.
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*/
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struct ap_matrix_dev {
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struct device device;
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atomic_t available_instances;
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struct ap_config_info info;
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struct list_head mdev_list;
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struct mutex lock;
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struct ap_driver *vfio_ap_drv;
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};
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extern struct ap_matrix_dev *matrix_dev;
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/**
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* The AP matrix is comprised of three bit masks identifying the adapters,
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* queues (domains) and control domains that belong to an AP matrix. The bits i
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* each mask, from least significant to most significant bit, correspond to IDs
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* 0 to 255. When a bit is set, the corresponding ID belongs to the matrix.
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*
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* @apm_max: max adapter number in @apm
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* @apm identifies the AP adapters in the matrix
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* @aqm_max: max domain number in @aqm
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* @aqm identifies the AP queues (domains) in the matrix
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* @adm_max: max domain number in @adm
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* @adm identifies the AP control domains in the matrix
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*/
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struct ap_matrix {
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unsigned long apm_max;
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DECLARE_BITMAP(apm, 256);
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unsigned long aqm_max;
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DECLARE_BITMAP(aqm, 256);
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unsigned long adm_max;
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DECLARE_BITMAP(adm, 256);
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};
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/**
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* struct ap_matrix_mdev - the mediated matrix device structure
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* @list: allows the ap_matrix_mdev struct to be added to a list
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* @matrix: the adapters, usage domains and control domains assigned to the
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* mediated matrix device.
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* @group_notifier: notifier block used for specifying callback function for
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* handling the VFIO_GROUP_NOTIFY_SET_KVM event
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* @kvm: the struct holding guest's state
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*/
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struct ap_matrix_mdev {
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struct list_head node;
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struct ap_matrix matrix;
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struct notifier_block group_notifier;
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struct notifier_block iommu_notifier;
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bool kvm_busy;
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wait_queue_head_t wait_for_kvm;
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struct kvm *kvm;
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struct kvm_s390_module_hook pqap_hook;
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struct mdev_device *mdev;
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};
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struct vfio_ap_queue {
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struct ap_matrix_mdev *matrix_mdev;
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unsigned long saved_pfn;
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int apqn;
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#define VFIO_AP_ISC_INVALID 0xff
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unsigned char saved_isc;
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};
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int vfio_ap_mdev_register(void);
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void vfio_ap_mdev_unregister(void);
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int vfio_ap_mdev_reset_queue(struct vfio_ap_queue *q,
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unsigned int retry);
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#endif /* _VFIO_AP_PRIVATE_H_ */
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