[PATCH v2 0/5] KVM: Clean up debugfs+stats init/destroy

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The way that KVM handles debugfs init/destroy is somewhat sloppy. Even
though debugfs is stood up after kvm_create_vm(), it is torn down from
kvm_destroy_vm(). There exists a window where we need to tear down a VM
before debugfs is created, requiring delicate handling.

This series cleans up the debugfs lifecycle by fully tying it to the
VM's init/destroy pattern.

First two patches hoist some unrelated stats initialization to a more
appropriate place for kvm and kvm_vcpu.

Second two patches are the meat of the series, changing around the
initialization order to get an FD early and wiring in debugfs
initialization to kvm_create_vm().

Lastly, patch 5 is essentially a revert of Sean's fix [1] for a NULL deref
in debugfs, though I stopped short of an outright revert since that one
went to stable and is still entirely correct.

Applies cleanly to v5.18-rc5, since [1] is currently missing from
kvm/queue or kvm/next. Tested with KVM selftests and the reproducer
mentioned in [1] on an Intel Skylake machine.

[1] 5c697c367a66 ("KVM: Initialize debugfs_dentry when a VM is created to avoid NULL deref")

v1: http://lore.kernel.org/r/20220415201542.1496582-1-oupton@xxxxxxxxxx

v1 -> v2:
 - Don't conflate debugfs+stats. Initialize stats_id outside of the
   context of debugfs (Sean)
 - Pass around the FD as a string to avoid subsequent KVM changes
   inappropriately using the FD (Sean)

Oliver Upton (5):
  KVM: Shove vm stats_id init into kvm_create_vm()
  KVM: Shove vcpu stats_id init into kvm_vcpu_init()
  KVM: Get an fd before creating the VM
  KVM: Actually create debugfs in kvm_create_vm()
  KVM: Hoist debugfs_dentry init to kvm_create_vm_debugfs() (again)

 virt/kvm/kvm_main.c | 96 +++++++++++++++++++++++----------------------
 1 file changed, 49 insertions(+), 47 deletions(-)

-- 
2.36.1.124.g0e6072fb45-goog




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