Re: [Xen-devel] [PATCH v3 02/11] hvm/hpet: Only call guest_time_hpet(h) one time per action.

[Don Slutz <dslutz@xxxxxxxxxxx>]

On 4/23/2014 11:07 AM, Jan Beulich wrote:
> > > > On 17.04.14 at 19:42, <dslutz@xxxxxxxxxxx> wrote:
> > v3:
> >    Did not add Reviewed-by (Jan Beulich) do to amount of change
> >    Added passing of guest_time to hpet_read64() and
> >      hpet_stop_timer().
> But that wasn't as a result of the review of v2, was it?
Not on this thread.  I was using gdb to get answers for a later patch.

>   Especially for
> the hpet_read64() case I fear this is going a little too far, since now
> you call the supposedly expensive function even when the value isn't
> needed. I suppose you could resolve this by passing a known-invalid
> value to the function from hpet_read() (so it knows to call
> guest_time_hpet() itself) and use the always-preset variant on from
> hpet_write().
I also considered a case statement on the call (since the value is 
needed later when
hpet_write also uses it).  I do not think that any value is invalid.

> Otoh I admit that the only supposedly frequently use operations
> ought to be the two ones needing the value, so perhaps the
> overhead for the other ones is tolerable. Let's see whether others
> have any opinion on this.
I also expect that the frequently used operations are the ones that need 
it.  And it
is the lower risk of add a bug.  Will wait for any other comments.

    -Don Slutz

> Apart from that I'm still fine with the patch.
>
> Jan

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel