The VM-exit instruction length(VMX_EXIT_INSTR_LEN) in VMCS is undefined
on EPT violation, except during delivery of a software interrupt,
privileged software exception, or software exception[1]. Although CPU
is likely to set the field, it can be incorrect in certain cases, such
as cmp+jcc and test+jcc.
Since hypervisor does not know exactly how much bytes needed, and GVA
translation is costly, it first copies at most 15 (VIE_INST_SIZE) bytes
within the page, then decodes the instruction. If more bytes are needed
during decoding and copied length is less than 15, it copies remaining
bytes.
[1] 29.2.5, https://cdrdv2-public.intel.com/671200/325462-sdm-vol-1-2abcd-3abcd.pdf
Tracked-On: #8756
Signed-off-by: Jiaqing Zhao <jiaqing.zhao@linux.intel.com>
3c6aa23ab2