Re: [Xen-devel] [PATCH] x86/hvm/viridian: set shutdown_code in response to CrashNotify

[Paul Durrant <Paul.Durrant@xxxxxxxxxx>]

> -----Original Message-----
> From: Andrew Cooper
> Sent: 10 August 2018 16:57
> To: Paul Durrant <Paul.Durrant@xxxxxxxxxx>; xen-devel@xxxxxxxxxxxxxxxxxxxx
> Cc: Jan Beulich <jbeulich@xxxxxxxx>
> Subject: Re: [PATCH] x86/hvm/viridian: set shutdown_code in response to
> CrashNotify
> 
> On 10/08/18 16:43, Paul Durrant wrote:
> > When Windows writes the CrashNotify bit in the CRASH_CTL MSR then we
> know
> > it is crashing, so set the domain shutdown code appropriately.
> >
> > Signed-off-by: Paul Durrant <paul.durrant@xxxxxxxxxx>
> > ---
> > Cc: Jan Beulich <jbeulich@xxxxxxxx>
> > Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> > ---
> >  xen/arch/x86/hvm/viridian.c | 4 ++++
> >  1 file changed, 4 insertions(+)
> >
> > diff --git a/xen/arch/x86/hvm/viridian.c b/xen/arch/x86/hvm/viridian.c
> > index 486065182c..294cf486cc 100644
> > --- a/xen/arch/x86/hvm/viridian.c
> > +++ b/xen/arch/x86/hvm/viridian.c
> > @@ -645,6 +645,10 @@ int wrmsr_viridian_regs(uint32_t idx, uint64_t val)
> >          if ( !ctl.u.CrashNotify )
> >              break;
> >
> > +        spin_lock(&d->shutdown_lock);
> > +        d->shutdown_code = SHUTDOWN_crash;
> > +        spin_unlock(&d->shutdown_lock);
> 
> How does the domain eventually shut down?

I assume it shuts down when the guest writes to the PIIX.

>  It feels slightly odd to have
> a shutdown code before the domain has finished executing code.
> 

That's the norm. The PV drivers (if they are installed) set it via a schedop. 
This just makes sure it is set even if the PV drivers aren't there.

  Paul

> ~Andrew
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