Re: [nvmx testing, linux on linux] Disabling EPT in L1 renders L2 stuck on boot

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Gleb, so I just did a trace of KVM MMU to try to understand why L2 is
stuck with shadow on EPT

Ensure, EPT is enabled on L0 & disabled on L1

On L0:
---------
  $ cat /sys/module/kvm_intel/parameters/ept
  Y

On L1
---------
  $ cat /sys/module/kvm_intel/parameters/ept
  N

Build and install trace-cmd on L1:

  $ git clone git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/trace-cmd.git
trace-cmd
  $ make && sudo make-install

Run trace command (on L1) to capture kvmmmu event:

  $ trace-cmd record -b 2000 -e kvmmmu
  /sys/kernel/debug/tracing/events/kvmmmu/filter
  /sys/kernel/debug/tracing/events/*/kvmmmu/filter
  Hit Ctrl^C to stop recording

Boot L2 guest:

  $ virsh start nguest-01 --console

After a minute or two, ctl-C the trace-cmd, generate the report:

  $ trace-cmd report
  version = 6
  trace-cmd: No such file or directory
    function is_writable_pte not defined
  CPU 1 is empty
  CPU 2 is empty
  CPU 3 is empty
  cpus=4
   qemu-system-x86-2554  [000] 90667.995345:
kvm_mmu_invalidate_zap_all_pages: kvm-mmu-valid-gen 0 used_pages 0
   qemu-system-x86-2557  [000] 90668.078978: kvm_mmu_get_page:     new
sp gfn 0 0/2 q0 direct --- !pge !nxe root 0 sync
   qemu-system-x86-2557  [000] 90668.078980: kvm_mmu_get_page:     new
sp gfn 40000 0/2 q0 direct --- !pge !nxe root 0 sync
   qemu-system-x86-2557  [000] 90668.078980: kvm_mmu_get_page:     new
sp gfn 80000 0/2 q0 direct --- !pge !nxe root 0 sync
   qemu-system-x86-2557  [000] 90668.078981: kvm_mmu_get_page:     new
sp gfn c0000 0/2 q0 direct --- !pge !nxe root 0 sync
   qemu-system-x86-2557  [000] 90668.079025: kvm_mmu_get_page:     new
sp gfn 0 0/1 q0 direct --- !pge !nxe root 0 sync

Side question:  I wonder why would trace-cmd say "trace-cmd: No such
file or directory"?

/kashyap
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