Re: [PATCH 1/3] s390/kvm: Set CPU in stopped state on initial cpu reset

[Christian Borntraeger <borntraeger@de.ibm.com>]

On 11/06/12 18:46, Alexander Graf wrote:
> On 06/11/2012 04:06 PM, Cornelia Huck wrote:
>> From: Christian Borntraeger<borntraeger@de.ibm.com>
>>
>> The initial cpu reset sets the cpu in the stopped state.
>> Several places check for the cpu state (e.g. sigp set prefix) and
>> not setting the STOPPED state triggered errors with newer guest
>> kernels after reboot.
>>
>> Signed-off-by: Christian Borntraeger<borntraeger@de.ibm.com>
>> Signed-off-by: Cornelia Huck<cornelia.huck@de.ibm.com>
> 
> Is this only broken as of now or has this been broken before? So do we need to send this to -stable for anyone? And what happens on RESET?

Looks like this problem appeared as a combination of newer guest kernels
(something like >=3.2 or so) with a reworked SMP bringup behaviour and a 
host fix (151104a7b3a82f9c56d636595ae58084049d2559 KVM: s390: make sigp 
restart return busy when stop pending)
which both are correct in itself but uncovered this third problem.

With this patch I have a qemu/kernel combination which works reliably with different
guest kernels for guest initiated resets as well as qemu monitor system_reset
as well as system_shutdown+system_reset+cont. It will probably not be the last
fix (e.g. initial reset should also take care of pending CPU local interrupts)
but we are making progress.

Christian

PS: The working combination has two patches pending for qemu which need some
cleanup, will send soon