Re: [Xen-devel] Xen HVM regression on certain Intel CPUs

["Xu, Dongxiao" <dongxiao.xu@xxxxxxxxx>]

> -----Original Message-----
> From: Keir Fraser [mailto:keir.xen@xxxxxxxxx]
> Sent: Wednesday, April 03, 2013 10:28 PM
> To: Jan Beulich; Stefan Bader
> Cc: xen-devel@xxxxxxxxxxxxxxxxxxx; Konrad Rzeszutek Wilk; Dong, Eddie;
> wei.y.yang@xxxxxxxxx; Shan, Haitao; Xu, Dongxiao; xin.li@xxxxxxxxx; Nakajima,
> Jun; H. Peter Anvin; Zhang, Xiantao
> Subject: Re: [Xen-devel] Xen HVM regression on certain Intel CPUs
> 
> On 03/04/2013 13:43, "Jan Beulich" <JBeulich@xxxxxxxx> wrote:
> 
> >>>> On 03.04.13 at 13:56, Stefan Bader <stefan.bader@xxxxxxxxxxxxx>
> wrote:
> >> I added some more debugging output to the hypervisor to verify the state of
> >> HAP.
> >> This showed that while HAP is available on the system, it is not used for 
> >> the
> >> HVM guests. It looks like this would require some flags to be set when
> >> creating
> >> the guest domains and I assume this is not happening because I have to stay
> >> with
> >> the xm stack for the libvirt setup for now (requires some repackaging which
> >> hasn't been done, yet).
> >>
> >> So the guest isn't using HAP but does seem to use some form of paging even
> if
> >> the guest VCPU is not using paging. So I changed the
> vmx_update_guest_cr()
> >> function in that way and that seems to prevent the hangs. Does this look 
> >> like
> >> a
> >> reasonable upstream Xen change?
> >
> > Yes, it looks appropriate. But I'd like this to be confirmed by the
> > authors of the original change and/or the VMX maintainers (added
> > to Cc).
> 
> It can have my ack straight away.
> 
> Acked-by: Keir Fraser <keir@xxxxxxx>
> 
> Nonetheless it would be nice to get a VMX maintainer ack too, though I'm
> pretty sure this patch is correct.

Yes, it is a good fix. Thank you!
I didn't test non-HAP case when I made the patch to fix this SMEP issue. 

Acked-by: Dongxiao Xu <dongxiao.xu@xxxxxxxxx>

Thanks,
Dongxiao

> 
>  -- Keir
> 
> > Nevertheless it's very odd to not use HAP on a machine capable
> > of it...
> >
> > Jan
> >
> >
> >
> >
> > _______________________________________________
> > Xen-devel mailing list
> > Xen-devel@xxxxxxxxxxxxx
> > http://lists.xen.org/xen-devel
> 


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