Re: [Xen-devel] [PATCH v3 7/9] xen/arm: vgic: Optimize the way to store the target vCPU in the rank

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Mon, 12 Oct 2015, Julien Grall wrote:
> On 12/10/15 11:41, Stefano Stabellini wrote:
> > On Thu, 8 Oct 2015, Ian Campbell wrote:
> >>> If the concern is the behavior is changed, I'm happy to rework this code
> >>> to keep exactly the same behavior. I.e any 32-bit write containing
> >>> a 0 byte will be ignored. This is not optimal but at least I'm not
> >>> opening the pandora box of fixing every single error in the code touch
> >>> by this series.
> >>
> >> I'm okay with the new behaviour, I think Stefano was willing to tolerate it
> >> (based on <alpine.DEB.2.02.1510081220190.1179@xxxxxxxxxxxxxxxxxxxxxxx>).
> >>
> >> So if we aren't going to fix it to DTRT WRT writing zero to a target then I
> >> think we can go with the current variant and not change to ignoring any
> >> word with a zero byte in it.
> >  
> > OK.
> > 
> > BTW it would be interesting to see how real hardware behaves in this
> > regard. I seem to recall that X-Gene was ignoring 0 writes too.
> 
> What do you mean by 0 writes? Is it the write ignored if one byte is 0?

Yes, for either 32bit or 8bit writes.


> Although, it's really depend if you try on a target register where all
> the byte correspond to an implemented field or not.

I am talking about implemented fields

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