Re: [Xen-devel] [PATCH] x86: re-enable VCPUOP_register_vcpu_time_memory_area

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

On Thu, 2013-05-16 at 17:15 +0100, Matt Wilson wrote:
> On Thu, May 16, 2013 at 04:01:33PM +0100, Jan Beulich wrote:
> > >>> On 16.05.13 at 16:40, Ian Campbell <ian.campbell@xxxxxxxxxx> wrote:
> > > On Thu, 2013-05-16 at 09:47 +0100, Jan Beulich wrote:
> > >> Regardless of the code freeze I'd still like to propose this for
> > >> inclusion in 4.3, mainly based on the fact that this got disabled late
> > >> in the 4.0 release cycle with the expectation that it would get
> > >> re-enabled soon after. Now that upstream Linux also has, as of 3.8 at
> > >> least on x86-64, the necessary hypervisor independent support code, it
> > >> would be odd to not leverage this on Xen.
> > > 
> > > I went looking for a call to VCPUOP_register_vcpu_time_memory_area in
> > > 3.10-rc1 and can't find it -- what have I missed?
> > 
> > The words "hypervisor independent" in my explanation. Iirc Jeremy
> > had a patch, and the non-Xen pieces got extracted from it for KVM
> > (in 3.8 I think). The Xen parts would need to be recovered and
> > pushed upstream. The way I did this for our kernel isn't even coming
> > close to what would be needed for upstreaming.
> 
> Does this look like the right bit of old code? 
>   https://lkml.org/lkml/2009/10/5/391

That looks like the xen bit but it seems incomplete -- I expect there is
a generic precursor somewhere.

The interesting upstream commits seem to be these two, although there
are various subsequent fixups as well.
        
        commit 3dc4f7cfb7441e5e0fed3a02fc81cdaabd28300a
        Author: Marcelo Tosatti <mtosatti@xxxxxxxxxx>
        Date:   Tue Nov 27 23:28:56 2012 -0200
        
            x86: kvm guest: pvclock vsyscall support
            
            Hook into generic pvclock vsyscall code, with the aim to
            allow userspace to have visibility into pvclock data.
            
            Signed-off-by: Marcelo Tosatti <mtosatti@xxxxxxxxxx>
        
        commit 71056ae22d43f58d7e0f793af18ace2eaf5b74eb
        Author: Marcelo Tosatti <mtosatti@xxxxxxxxxx>
        Date:   Tue Nov 27 23:28:55 2012 -0200
        
            x86: pvclock: generic pvclock vsyscall initialization
            
            Originally from Jeremy Fitzhardinge.
            
            Introduce generic, non hypervisor specific, pvclock initialization
            routines.
            
            Signed-off-by: Marcelo Tosatti <mtosatti@xxxxxxxxxx>

Ian.


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