Re: [Xen-devel] [Patch] x86emul: simplify prefix handling for VMFUNC

["Lai, Paul" <paul.c.lai@xxxxxxxxx>]

On Wed, Sep 21, 2016 at 02:39:58AM -0600, Jan Beulich wrote:
> >>> On 21.09.16 at 00:35, <paul.c.lai@xxxxxxxxx> wrote:
> > On Tue, Sep 20, 2016 at 09:50:15AM -0600, Jan Beulich wrote:
> >> 
> >> Paul, there's been no reply to
> >> https://lists.xenproject.org/archives/html/xen-devel/2016-09/msg00380.html 
> > 
> > The refered to patch, commit a1b1572833, adds a check for vmfunc.
> > I look a little time to look at the SDM and finally found the reference.
> > The vmfunc can be found in Table A-6 "Opcode Extensions for One- and Two-
> > byte Opcodes by Group Number" on page A-18 Vol. 2D of the
> >  e64-ia-32-architectures-software-developer-manual-325462.pdf.
> > The values for vmfunc match the values in the code.
> > I also took the liberty of looking at the other existing cases in the
> > switch statement, and can find RDTSCP and INVLPG. The CLZERO extension
> > value is a mystery to me.
> 
> Well - the question raised was whether the documentation is
> perhaps wrong.

VMFUNC allowing 66, F2, and F3 prefixes when
> other opcodes in its neighborhood (e.g. xsetbv, xtest, xend)
> don't seems at least suspicious. 

Thanks for the clearer problem statement. 

> Extensions originating from AMD
> (rdtscp, clzero) can't be reasonably taken for reference.
> 
> Jan
> 

I'll check....


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