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commitc43120afb5upstream. kvm->lock must be taken outside of the vcpu->mutex. Of course, the locking documentation for KVM makes this abundantly clear. Nonetheless, the locking order in KVM/arm64 has been wrong for quite a while; we acquire the kvm->lock while holding the vcpu->mutex all over the shop. All was seemingly fine until commit42a90008f8("KVM: Ensure lockdep knows about kvm->lock vs. vcpu->mutex ordering rule") caught us with our pants down, leading to lockdep barfing: ====================================================== WARNING: possible circular locking dependency detected 6.2.0-rc7+ #19 Not tainted ------------------------------------------------------ qemu-system-aar/859 is trying to acquire lock: ffff5aa69269eba0 (&host_kvm->lock){+.+.}-{3:3}, at: kvm_reset_vcpu+0x34/0x274 but task is already holding lock: ffff5aa68768c0b8 (&vcpu->mutex){+.+.}-{3:3}, at: kvm_vcpu_ioctl+0x8c/0xba0 which lock already depends on the new lock. Add a dedicated lock to serialize writes to VM-scoped configuration from the context of a vCPU. Protect the register width flags with the new lock, thus avoiding the need to grab the kvm->lock while holding vcpu->mutex in kvm_reset_vcpu(). Cc: stable@vger.kernel.org Reported-by: Jeremy Linton <jeremy.linton@arm.com> Link: https://lore.kernel.org/kvmarm/f6452cdd-65ff-34b8-bab0-5c06416da5f6@arm.com/ Tested-by: Jeremy Linton <jeremy.linton@arm.com> Signed-off-by: Oliver Upton <oliver.upton@linux.dev> Signed-off-by: Marc Zyngier <maz@kernel.org> Link: https://lore.kernel.org/r/20230327164747.2466958-3-oliver.upton@linux.dev Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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.