Re: [Xen-devel] Ping: [PATCH 0/4] HVM: produce better binary code

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 04/09/13 11:06, Jan Beulich wrote:
>>>> On 23.08.13 at 15:58, "Jan Beulich" <JBeulich@xxxxxxxx> wrote:
> While I got two reviews meanwhile for this series (thanks Andrew
> and Tim!), ack-s from the maintainers are still missing:
>
>> 1: VMX: streamline entry.S code
>> 2: VMX: move various uses of UD2 out of fast paths
>> 3: VMX: use proper instruction mnemonics if assembler supports them
> Jun, Eddie? (Yes, there had been a couple of revisions to patches
> 2 and 3, but even their sending was now more than a week ago.)
>
>> 4: SVM: streamline entry.S code
> Suravee, Boris, Jacob?
>
> I'm going to wait a for perhaps another day or two, and will assume
> silent agreement if I don't hear otherwise. I'll similarly assume silent
> agreement to the discussed follow-up patches (dropping memory
> barriers in a few places as well as converting __vmread() along the
> lines of __vmread_safe()) once done, submitted, and reviewed.
>
> Jan
>

One thing I have noticed from subsequent reading of processor manuals is
that reading from control registers are not actually serialising.  It
would be useful to get some comments about the in-processor optimisation
for runs of pushes/pops, to determine whether it is a good idea
interrupting the run.  Having said that, the changes of any difference
being measurable is slim.

~Andrew

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