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

[Andrew Cooper <andrew.cooper3@citrix.com>]

On 06/09/18 16:32, Paul Durrant wrote:
>> -----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?

Lol - I was literally just trying to find it.  I'll commit it in a moment.

~Andrew

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