From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christian Borntraeger Subject: Re: [PATCH/RFC] KVM: track pid for VCPU only on KVM_RUN ioctl Date: Tue, 19 Aug 2014 12:09:43 +0200 Message-ID: <53F32267.6090106@de.ibm.com> References: <1407249854-2953-1-git-send-email-borntraeger@de.ibm.com> <53E38193.8060206@redhat.com> <53F30CF3.5030606@de.ibm.com> <53F3187E.6080706@redhat.com> <53F31D35.4010901@de.ibm.com> <53F31E9F.9020402@redhat.com> <53F32005.2060902@de.ibm.com> <53F320E8.3040502@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Transfer-Encoding: 7bit Cc: KVM , Gleb Natapov , Rik van Riel , Raghavendra K T , Michael Mueller To: Paolo Bonzini Return-path: Received: from e06smtp15.uk.ibm.com ([195.75.94.111]:53403 "EHLO e06smtp15.uk.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750779AbaHSKJx (ORCPT ); Tue, 19 Aug 2014 06:09:53 -0400 Received: from /spool/local by e06smtp15.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 19 Aug 2014 11:09:51 +0100 Received: from b06cxnps3074.portsmouth.uk.ibm.com (d06relay09.portsmouth.uk.ibm.com [9.149.109.194]) by d06dlp02.portsmouth.uk.ibm.com (Postfix) with ESMTP id BFAC72190023 for ; Tue, 19 Aug 2014 11:09:31 +0100 (BST) Received: from d06av04.portsmouth.uk.ibm.com (d06av04.portsmouth.uk.ibm.com [9.149.37.216]) by b06cxnps3074.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id s7JA9nFF36438220 for ; Tue, 19 Aug 2014 10:09:49 GMT Received: from d06av04.portsmouth.uk.ibm.com (localhost [127.0.0.1]) by d06av04.portsmouth.uk.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id s7JA9lXB027491 for ; Tue, 19 Aug 2014 04:09:48 -0600 In-Reply-To: <53F320E8.3040502@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On 19/08/14 12:03, Paolo Bonzini wrote: > Il 19/08/2014 11:59, Christian Borntraeger ha scritto: >> Its only for the interrupts that are cpu local (like pending IPIs). >> In addition, we would do that only for the reset case (with an >> interface that can be used for migration). Right now >> KVM_S390_INITIAL_RESET takes the vcpu_mutex, so this protects against >> KVM_RUN. > > 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. Christian