'repz' instruction not supported.

[Ashutosh Kumar]

Thanks.  Will share the code sometime this week with you.

Regards
Ashutosh

> Date: Fri, 21 Nov 2014 11:22:06 -0800
> Subject: Re: 'repz' instruction not supported.
> From: neelnatu at gmail.com
> To: mrashutosh at hotmail.com
> CC: freebsd-virtualization at freebsd.org
> 
> Hi Ashutosh,
> 
> On Fri, Nov 21, 2014 at 2:07 AM, Ashutosh Kumar <mrashutosh at hotmail.com> wrote:
> > Yes you are right 'repz' prefixes is added to the ‘cmps’ and 'scas'
> > instructions.
> >
> > The actual opcode is “F3 A5” which is ‘rep movs’ (disassembly is showing
> > ‘repz’).
> >
> >
> >
> > Yes the guest is emitting these instructions to access MMIO (local apic)
> >
> 
> Bummer.
> 
> I was hoping that it was a prefix stuck by the compiler for
> optimization (that could be ignored):
> http://repzret.org/p/repzret/
> 
> In any case, the primitives you will need to emulate MOVS exist in
> vmm_instruction_emul.c. I don't have any plans to work on this but
> would be happy to review/submit the patch that does the emulation.
> 
> best
> Neel
> 
> >
> >
> > Regards
> > Ashutosh
> >
> >
> >> Date: Fri, 21 Nov 2014 00:08:15 -0800
> >> Subject: Re: 'repz' instruction not supported.
> >> From: neelnatu at gmail.com
> >> To: mrashutosh at hotmail.com
> >> CC: freebsd-virtualization at freebsd.org
> >
> >>
> >> 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?
> >>
> >> best
> >> Neel
> >>
> >> > RegardsAshutosh
> >> > _______________________________________________
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