Re: [Xen-devel] Save paused cpu ctx

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Wed, Sep 19, 2018 at 12:02:05PM +0300, Isaila Alexandru wrote:
> On Wed, 2018-09-19 at 10:41 +0200, Roger Pau Monné wrote:
> > On Wed, Sep 19, 2018 at 11:21:32AM +0300, Isaila Alexandru wrote:
> > > Hello, 
> > > 
> > > I want to restart the discussion on dropping the "if ( v-
> > > >pause_flags &
> > > VPF_down )" from hvm_save_cpu_ctxt() and be able to save context in
> > > a
> > > vcup down state. The content of the ctx could be filled like it is
> > > described in Intel SDM, "9.1.1 Processor State After Reset" (https:
> > > //so
> > > ftware.intel.com/sites/default/files/managed/39/c5/325462-sdm-vol-
> > > 1-
> > > 2abcd-3abcd.pdf   page 2996).
> > 
> > If the point is filling the context with the default reset state why
> > can't this be done by the tools if required?
> > 
> > It seems like saving the state of down vCPUs is quite pointless since
> > the state is always going to be the same, and will just increase the
> > size of the migration stream, but maybe I'm missing something.
> > 
> The idea behind this is to be able to query a vcpu and have it's state
> because right now xen does not return any info about a vcpu if it's
> down. 
> 
> We do not want to save the context but just to get info about it as a
> result of a query.

Can you infer that vCPUs that don't have a context are down?

Roger.

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