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

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

On Fri, Aug 31, 2018 at 04:56:21PM +0300, Isaila Alexandru wrote:
> On Mi, 2018-08-29 at 08:13 -0600, Jan Beulich wrote:
> > > 
> > > > 
> > > > > 
> > > > > On 29.08.18 at 16:02, <aisaila@xxxxxxxxxxxxxxx> wrote:
> > > 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:
> > > > > 
> > > > > 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
> > > Is this urgent to be in this series? If not I will add a new patch
> > > after it is all in. 
> > Considering the problems that there have been with this series,
> > anything to help build confidence in things still working for all
> > cases would help here, so I'm pretty glad Roger thought of this,
> > and while I wouldn't make it as strong as "the series can't go
> > in without this", I'd still much prefer if you too the time.
> 
> I don't think it is possible to use getcontext_partial() in vcpu_hvm()
> because of the need to have a header for xc_domain_hvm_setcontext() and
> the only way to get it is by xc_domain_hvm_getcontext(). There is also
> a comment there that states the same thing
> "/*
>      * Get the full HVM context in order to have the header, it is not
>      * possible to get the header with getcontext_partial, and crafting
> one
>      * from userspace is also not an option since cpuid is trapped and
>      * modified by Xen.
>      */
> "
> I hope I understood the request correctly to start with and if not
> please clarify. 

But I expect you also get such header when fetching the state of a
single device, or else how do you use this new hypercall in
conjunction with xc_domain_hvm_setcontext?

Thanks, Roger.

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