[GIT PULL] KVM: Async #PF changes for 6.9

[Sean Christopherson <seanjc@google.com>]

Fix a long-standing bug in the async #PF code where KVM code could be left
running in a workqueue even after all *external* references to KVM-the-module
have been put, and a few minor cleanups on top.

The following changes since commit 41bccc98fb7931d63d03f326a746ac4d429c1dd3:

  Linux 6.8-rc2 (2024-01-28 17:01:12 -0800)

are available in the Git repository at:

  https://github.com/kvm-x86/linux.git tags/kvm-x86-asyncpf-6.9

for you to fetch changes up to c2744ed2230a92636f04cde48f2f7d8d3486e194:

  KVM: Nullify async #PF worker's "apf" pointer as soon as it might be freed (2024-02-06 11:04:58 -0800)

----------------------------------------------------------------
KVM async page fault changes for 6.9:

 - Always flush the async page fault workqueue when a work item is being
   removed, especially during vCPU destruction, to ensure that there are no
   workers running in KVM code when all references to KVM-the-module are gone,
   i.e. to prevent a use-after-free if kvm.ko is unloaded.

 - Grab a reference to the VM's mm_struct in the async #PF worker itself instead
   of gifting the worker a reference, e.g. so that there's no need to remember
   to *conditionally* clean up after the worker.

----------------------------------------------------------------
Sean Christopherson (4):
      KVM: Always flush async #PF workqueue when vCPU is being destroyed
      KVM: Put mm immediately after async #PF worker completes remote gup()
      KVM: Get reference to VM's address space in the async #PF worker
      KVM: Nullify async #PF worker's "apf" pointer as soon as it might be freed

 include/linux/kvm_host.h |  1 -
 virt/kvm/async_pf.c      | 73 ++++++++++++++++++++++++++++++++----------------
 2 files changed, 49 insertions(+), 25 deletions(-)