mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2026-09-22 09:34:56 +02:00
Tony Krowiak
21195eb038
The vfio_ap device driver registers for notification when the pointer to the KVM object for a guest is set. Recall that the KVM lock (kvm->lock) mutex must be taken outside of the matrix_dev->lock mutex to prevent the reporting by lockdep of a circular locking dependency (a.k.a., a lockdep splat): * see commit0cc00c8d40("Fix circular lockdep when setting/clearing crypto masks") * see commit86956e7076("replace open coded locks for VFIO_GROUP_NOTIFY_SET_KVM notification") With the introduction of support for hot plugging/unplugging AP devices passed through to a KVM guest, a new guests_lock mutex is introduced to ensure the proper locking order is maintained: struct ap_matrix_dev { ... struct mutex guests_lock; ... } The matrix_dev->guests_lock controls access to the matrix_mdev instances that hold the state for AP devices that have been passed through to a KVM guest. This lock must be held to control access to the KVM pointer (matrix_mdev->kvm) while the vfio_ap device driver is using it to plug/unplug AP devices passed through to the KVM guest. Keep in mind, the proper locking order must be maintained whenever dynamically updating a KVM guest's APCB to plug/unplug adapters, domains and control domains: 1. matrix_dev->guests_lock: required to use the KVM pointer - stored in a struct ap_matrix_mdev instance - to update a KVM guest's APCB 2. matrix_mdev->kvm->lock: required to update a guest's APCB 3. matrix_dev->mdevs_lock: required to access data stored in a struct ap_matrix_mdev instance. Signed-off-by: Tony Krowiak <akrowiak@linux.ibm.com> Reviewed-by: Jason J. Herne <jjherne@linux.ibm.com> Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.