From mboxrd@z Thu Jan  1 00:00:00 1970
From: Paolo Bonzini <pbonzini@redhat.com>
Subject: Re: [PATCH/RFC] KVM: track pid for VCPU only on KVM_RUN ioctl
Date: Tue, 19 Aug 2014 12:31:41 +0200
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Cc: KVM <kvm@vger.kernel.org>, Gleb Natapov <gleb@kernel.org>,
	Rik van Riel <riel@redhat.com>,
	Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>,
	Michael Mueller <mimu@linux.vnet.ibm.com>
To: Christian Borntraeger <borntraeger@de.ibm.com>
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Il 19/08/2014 12:09, Christian Borntraeger ha scritto:
>> I'm not sure, this does seem like a workaround for another
>> limitation after all...  Gleb?
>
> Yes. We want to get rid of KVM_S390_INITIAL_RESET in QEMU. This comes
> from a time, when we had another userspace prototype for KVM on s390
> (kuli). Its really a wart that has to go. Its just that we are not
> there yet to remove the call to KVM_S390_INITIAL_RESET. Doing so can
> result in hard to debug errors after reboot, if an interrupt was made
> pending just before reboot that gets delivered in the new instance.
> 
> The new way for local interrupt read/write will probably be some
> onereg or syncreg interface with a bitmask register and payload
> registers. We have to solve some concurrency and implemenation issues
> here.

Yes, I understand; the plan is fine and it's good that it was already on
your todo list.

But since you acknowledge that KVM_S390_INITIAL_RESET will go, I'm not
sure we want to apply this patch (except for the pid == 0 part, of
course---that one is good).

Paolo