[Bug 215964] New: nVMX: KVM(L0) does not perform a platform reboot when guest(L2) trigger a reboot event through IO-Port-0xCF9

[bugzilla-daemon@kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=215964

            Bug ID: 215964
           Summary: nVMX: KVM(L0) does not perform a platform reboot when
                    guest(L2) trigger a reboot event through IO-Port-0xCF9
           Product: Virtualization
           Version: unspecified
    Kernel Version: 5.10+
          Hardware: Intel
                OS: Linux
              Tree: Mainline
            Status: NEW
          Severity: high
          Priority: P1
         Component: kvm
          Assignee: virtualization_kvm@kernel-bugs.osdl.org
          Reporter: yadong.qi@intel.com
        Regression: No

Background:
  We have a lightweight Hypervisor(iKGT) which aims to monitor very limited
resources and passthrough most resources to its guest. The IO-Port:0x3F9 is
also passthrough to its guest, so when guest tries to trigger a reboot
event(through IO-port:0x3F9), the hardware will do the platform reset directly.
  We ported it to running under KVM, then it becomes nested virtualization
architecture: KVM(L0), iKGT(L1), Guest(L2). 


Reproduce Steps:
  Guest(L2) write 0xCF9 to trigger a platform reboot.

Expected result:
  KVM perform a virtual platform reset and reboot guest.

Current result:
  It seems KVM only reset part of the vCPU(L2), but it does not clear the nVMX
state, it still tries to emulate VMExit to iKGT(L1). We still can observe
VMExit from iKGT(L1) and the exit reason is not expected.

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