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

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

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@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.

What happens if the user has configured windows to reboot after a crash?

~Andrew

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