'repz' instruction not supported.

Neel Natu neelnatu at gmail.com
Fri Nov 21 08:08:18 UTC 2014

Hi Ashutosh,

On Wed, Nov 19, 2014 at 10:30 PM, Ashutosh Kumar <mrashutosh at hotmail.com> wrote:
> Hi
> We have found that emulation of 'repz' instruction is not supported in bhyve. This is causing VM_EXIT for Guest OS. Do we have plans to add support for instructions like 'repz'.

'repz' is actually an instruction prefix. The two instructions with
which 'repz' is allowed are 'cmps' and 'scas'. Both these instructions
typically don't need to be emulated since they operate on strings in
"regular" guest memory.

Is your guest emitting these instructions to access MMIO? Can you
share an objdump with the offending instructions?


> RegardsAshutosh
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