Re: [Xen-devel] xc_altp2m_set_vcpu_enable_notify fail

[Big Strong <fangtuo90@xxxxxxxxx>]

Check the errno please, thats' where the information is stored.

I looked up in the source code of xen 4.6, and find that errno 4 indicates "Interrupted system call", I'm not sure if it is the cause.

Another information about VMFUNC error is from the Intel Manual:

25.5.5.2 General Operation of the VMFUNC Instruction
The VMFUNC instruction causes an invalid-opcode exception (#UD) if the “enable VM functions” VM-execution
controls is 0 or the value of EAX is greater than 63 (only VM functions 0–63 can be enable). Otherwise, the
instruction causes a VM exit if the bit at position EAX is 0 in the VM-function controls (the selected VM function is
not enabled). If such a VM exit occurs, the basic exit reason used is 59 (3BH), indicating “VMFUNC”, and the length
of the VMFUNC instruction is saved into the VM-exit instruction-length field. If the instruction causes neither an
invalid-opcode exception nor a VM exit due to a disabled VM function, it performs the functionality of the
VM function specified by the value in EAX.

 i.e. In conditions when guest software invoked a VM function with the VMFUNC instruction and the VM function either was not

enabled or generated a function-specific condition causing a VM exit.

But I've already enabled VM function and the conditions described in the manual are not true (EAX is 0), so I'm still not clear the real reason

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