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

[Paul Durrant <Paul.Durrant@citrix.com>]

> -----Original Message-----
> From: Xen-devel [mailto:xen-devel-bounces@lists.xenproject.org] On Behalf
> Of Paul Durrant
> Sent: 23 August 2018 09:38
> To: Andrew Cooper <Andrew.Cooper3@citrix.com>; xen-
> devel@lists.xenproject.org
> Cc: Jan Beulich <jbeulich@suse.com>
> Subject: Re: [Xen-devel] [PATCH] x86/hvm/viridian: set shutdown_code in
> response to CrashNotify
> 
> > -----Original Message-----
> > From: Andrew Cooper
> > Sent: 16 August 2018 10:40
> > To: Paul Durrant <Paul.Durrant@citrix.com>; xen-
> devel@lists.xenproject.org
> > Cc: Jan Beulich <jbeulich@suse.com>
> > Subject: Re: [PATCH] x86/hvm/viridian: set shutdown_code in response to
> > CrashNotify
> >
> > On 10/08/18 16:59, Paul Durrant wrote:
> > >> -----Original Message-----
> > >> From: Andrew Cooper
> > >> Sent: 10 August 2018 16:57
> > >> To: Paul Durrant <Paul.Durrant@citrix.com>; xen-
> > devel@lists.xenproject.org
> > >> Cc: Jan Beulich <jbeulich@suse.com>
> > >> 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@citrix.com>
> > >>> ---
> > >>> Cc: Jan Beulich <jbeulich@suse.com>
> > >>> Cc: Andrew Cooper <andrew.cooper3@citrix.com>
> > >>> ---
> > >>>  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.
> >
> > What happens if the user has configured windows to reboot after a crash?
> >
> 
> That's exactly what this is trying to fix. Without the patch a VM without PV
> drivers will appear to just shut down (because nothing will set the shutdown
> code to anything else) so the actions-after-crash will not take effect.
> 

Ping? Are you ok with the patch now?

  Paul

>   Paul
> 
> > ~Andrew
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