Re: [Xen-devel] [PATCH v17 13/13] x86/domctl: Don't pause the whole domain if only getting vcpu state

[Isaila Alexandru <aisaila@xxxxxxxxxxxxxxx>]

On Mi, 2018-08-22 at 18:15 +0300, Isaila Alexandru wrote:
> On Mi, 2018-08-22 at 16:41 +0200, Roger Pau Monné wrote:
> > 
> > On Wed, Aug 22, 2018 at 05:02:43PM +0300, Alexandru Isaila wrote:
> > > 
> > > 
> > > This patch is focused on moving changing hvm_save_one() to save
> > > one
> > > typecode from one vcpu and now that the save functions get data
> > > from a
> > > single vcpu we can pause the specific vcpu instead of the domain.
> > With this infrastructure added allowing to save a single instance
> > of
> > a
> > specific device I wonder if you would like to add a user to the
> > code
> > in the tree.
> > 
> > If you look at vcpu_hvm in tools/libxc/xc_dom_x86.c it saves the
> > full
> > domain context just to get the CPU and the MTRR state of VCPU#0. Do
> > you think you could switch this code to use the newly introduced
> > machinery to save a single instance of a specific type?
> Sure, I will add a tool patch at the end of the series

Hi Roger, 

Is this urgent to be in this series? If not I will add a new patch
after it is all in. 

Thanks, 
Alex
> > 
> > 
> > > 
> > > 
> > > Signed-off-by: Alexandru Isaila <aisaila@xxxxxxxxxxxxxxx>
> > > 
> > > ---
> > > Changes since V15:
> > >   - Moved pause/unpause calls into hvm_save_one()
> > >   - Re-add the loop in hvm_save_one().
> > > ---
> > >  xen/arch/x86/domctl.c   |  2 --
> > >  xen/arch/x86/hvm/save.c | 12 ++++++++++--
> > >  2 files changed, 10 insertions(+), 4 deletions(-)
> > > 
> > > diff --git a/xen/arch/x86/domctl.c b/xen/arch/x86/domctl.c
> > > index 8fbbf3a..cb53980 100644
> > > --- a/xen/arch/x86/domctl.c
> > > +++ b/xen/arch/x86/domctl.c
> > > @@ -591,12 +591,10 @@ long arch_do_domctl(
> > >               !is_hvm_domain(d) )
> > >              break;
> > >  
> > > -        domain_pause(d);
> > >          ret = hvm_save_one(d, domctl->u.hvmcontext_partial.type,
> > >                             domctl-
> > > >u.hvmcontext_partial.instance,
> > >                             domctl->u.hvmcontext_partial.buffer,
> > >                             &domctl->u.hvmcontext_partial.bufsz);
> > > -        domain_unpause(d);
> > >  
> > >          if ( !ret )
> > >              copyback = true;
> > > diff --git a/xen/arch/x86/hvm/save.c b/xen/arch/x86/hvm/save.c
> > > index 49741e0..2d35f17 100644
> > > --- a/xen/arch/x86/hvm/save.c
> > > +++ b/xen/arch/x86/hvm/save.c
> > > @@ -149,12 +149,15 @@ int hvm_save_one(struct domain *d, unsigned
> > > int typecode, unsigned int instance,
> > >          instance >= d->max_vcpus )
> > >          return -ENOENT;
> > >      ctxt.size = hvm_sr_handlers[typecode].size;
> > > -    if ( hvm_sr_handlers[typecode].kind == HVMSR_PER_VCPU )
> > > -        ctxt.size *= d->max_vcpus;
> > This chunk seems to belong to a different patch?
> > 
> > The change just mentions pausing a vpcu instead of the whole
> > domain,
> > but the size of the save context doesn't depend on whether the
> > whole
> > domain is paused vs a single vcpu is paused.
> Right, git rebase did not report any error so it tricked me. I will
> have that removed from this patch. 
> 
> Thanks, 
> Alex
> 
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