Re: [Xen-devel] Test if on newer xen all SSE2 and SSE3 instructions are effectively working

[Fabio Fantoni <fabio.fantoni@xxxxxxx>]

Il 22/11/2013 13:16, Jan Beulich ha scritto:
> > > > On 22.11.13 at 13:14, Fabio Fantoni <fabio.fantoni@xxxxxxx> wrote:
> > Il 21/11/2013 16:38, Andrew Cooper ha scritto:
> > > On 21/11/13 15:32, George Dunlap wrote:
> > > > On 21/11/13 15:22, Andrew Cooper wrote:
> > > > > On 21/11/13 15:12, George Dunlap wrote:
> > > > > > On Thu, Nov 21, 2013 at 10:52 AM, Fabio Fantoni
> > > > > > <fabio.fantoni@xxxxxxx> wrote:
> > > > > > > I'm trying to test if on newer xen all SSE2 and SSE3 instructions are
> > > > > > > effectively working.
> > > > > > > I tried this simple program to test SSE2:
> > > > > > > http://forum.nasm.us/index.php?topic=1605.0
> > > > > > > But probably use only instructions with short operand because SSE2
> > > > > > > on this
> > > > > > > program is working also on old xen 4.0 where Jan Beulich patches to
> > > > > > > support
> > > > > > > long operands are missing.
> > > > > > > Are there any minimal program to test if SSE instructions with MMIO
> > > > > > > operands
> > > > > > > > 8 byte are working?
> > > > > > I don't see the code there doing MMIO -- it's just doing operations on
> > > > > > normal RAM, which is not emulated by Xen at all, but executed natively
> > > > > > by the processor.
> > > > > >
> > > > > > What you need is a program that will do this to an MMIO region -- that
> > > > > > will be a much trickier thing to set up, I think.
> > > > > >
> > > > > >     -George
> > > > > The problem with SSE is only when the guest performs an SSE (or larger)
> > > > > operation on a piece of memory which ends up being emulated and handed
> > > > > to qemu.  The ioreq protocol doesn't have a way of signalling an operand
> > > > > width greater than 64 bits.
> > > > I'd like to emphasize the "and" in the first sentence.  You might be
> > > > able to trigger a Xen emulation in any number of ways (disabling HAP
> > > > and then doing an SSE instruction on an in-use PT might do it).  But
> > > > Xen allegedly already does the actual emulation correctly -- as Andy
> > > > said, it's only the path to qemu that wasn't working before.
> > > >
> > > >    -George
> > > Oops yes - I should have emphasised that a bit more.  I believe Jan
> > > submitted a hacked-fix for the qemu path which fixes the immediate issue
> > > (for 128bit emulation) but is in need of a redesign for wider emulation;
> > > 256bit is available with AVX, and 512bit is on its way with AVX2.
> > >
> > > As for testing individual instructions, there is
> > > tools/tests/x86_emulator/test_x86_emulator.c which tests a token few
> > > instructions against Xen's emulation code, but it is far from comprehensive.
> > >
> > > ~Andrew
> > Thanks for all replies.
> > I tried x86_emulator on dom0 and SSE2 instructions seems ok:
> Sure. Which means you still didn't understand that you need to
> try with SSE instructions accessing MMIO where the emulation
> happens in qemu.
>
> Jan
I have understood that this test needs to be tried inside hvm domUs (as 
I have posted in my previous mail):
> Same result on linux hvm domUs.
What I do not understand if is there is a test to accessing MMIO with 
SEE2 on x86_emulator and if not, an alternate way to make this check.
Thanks for any reply.

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