Re: [Qemu-devel] [PATCH] target-i386: enable cflushopt/clwb/pcommit instructions

[Eduardo Habkost]

On Thu, Nov 05, 2015 at 08:51:24AM +0100, Richard Henderson wrote:
> On 11/04/2015 08:35 PM, Eduardo Habkost wrote:
> >On Fri, Oct 30, 2015 at 01:54:33PM -0700, Richard Henderson wrote:
> >>On 10/29/2015 12:31 AM, Xiao Guangrong wrote:
> >>>These instructions are used by NVDIMM drivers and the specification
> >>>locates at:
> >>>https://software.intel.com/sites/default/files/managed/0d/53/319433-022.pdf
> >>>
> >>>There instructions are available on Skylake Server
> >>>
> >>>Signed-off-by: Xiao Guangrong <address@hidden>
> >>>---
> >>>  target-i386/cpu.c | 8 +++++---
> >>>  target-i386/cpu.h | 3 +++
> >>>  2 files changed, 8 insertions(+), 3 deletions(-)
> >>
> >>Reviewed-by: Richard Henderson <address@hidden>
> >>
> >>Although it would be nice to update the comments in translate.c to include 
> >>the
> >>new insns, since they overlap mfence and sfence.  At present we only check 
> >>for
> >>SSE enabled when accepting these; I suppose it's easiest to consider it 
> >>invalid
> >>to specify +clwb,-sse?
> >
> >I assume you want to add the extra SSE requirement to TCG code, not to
> >generic x86 code, then I have no objections.
> 
> I don't really want to add any requirement, just point and laugh at anyone
> who reports an bug for the above condition.
> 
> >But in the case of clwb (/6 with a memory operand, modrm != 0xc0), we
> >are not just requiring SSE2: we are rejecting the instruction unless
> >modrm == 0xc0. That means TCG is rejecting the clwb instruction, so I
> >believe we shouldn't add CLWB to TCG_7_0_EBX_FEATURES yet.
> 
> Hmm, yes.
> 
> I've cleaned up some of this code on a branch, but it didn't get enough
> testing or review this cycle, so it's going to wait for the next.  I see
> you've posted a patch for this, which should be good enough until then.

I will apply this patch without the TCG_*_FEATURES changes until we
change TCG, then. That's OK?

About the TCG patches I have sent, please let me know if they look good
and appropriate for 2.5. This is the first time I have touched TCG code.

-- 
Eduardo