From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:37900) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dVfgr-0005x5-2P for qemu-devel@nongnu.org; Thu, 13 Jul 2017 11:06:06 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dVfgo-0001NX-D2 for qemu-devel@nongnu.org; Thu, 13 Jul 2017 11:06:05 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:60223) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1dVfgo-0001ND-30 for qemu-devel@nongnu.org; Thu, 13 Jul 2017 11:06:02 -0400 Received: from pps.filterd (m0098396.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.21/8.16.0.21) with SMTP id v6DF5v3q104481 for ; Thu, 13 Jul 2017 11:05:59 -0400 Received: from e14.ny.us.ibm.com (e14.ny.us.ibm.com [129.33.205.204]) by mx0a-001b2d01.pphosted.com with ESMTP id 2bnt3pv9gj-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Thu, 13 Jul 2017 11:05:59 -0400 Received: from localhost by e14.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Thu, 13 Jul 2017 11:05:51 -0400 References: <1499942429-55449-1-git-send-email-borntraeger@de.ibm.com> <1499942429-55449-4-git-send-email-borntraeger@de.ibm.com> <20170713142721.3a40e083@gondolin> <1798a9f2-63f0-ab03-11ad-5513d9a90da9@linux.vnet.ibm.com> <20170713144941.GD2121@work-vm> From: Christian Borntraeger Date: Thu, 13 Jul 2017 17:05:45 +0200 MIME-Version: 1.0 In-Reply-To: <20170713144941.GD2121@work-vm> Content-Type: text/plain; charset=utf-8 Content-Language: en-IE Content-Transfer-Encoding: 8bit Message-Id: <99be1408-f8e4-7ecb-f47e-9de94a20ff18@de.ibm.com> Subject: Re: [Qemu-devel] [PATCH/s390-next 3/3] s390x/flic: migrate ais states List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Dr. David Alan Gilbert" , Halil Pasic Cc: Cornelia Huck , Juan Quintela , Yi Min Zhao , Pierre Morel , qemu-devel , Alexander Graf , Thomas Huth , Richard Henderson On 07/13/2017 04:49 PM, Dr. David Alan Gilbert wrote: > * Halil Pasic (pasic@linux.vnet.ibm.com) wrote: >> >> >> On 07/13/2017 02:27 PM, Cornelia Huck wrote: >>>> +static void kvm_flic_ais_pre_save(void *opaque) >>>> +{ >>>> + KVMS390FLICStateMigTmp *tmp = opaque; >>>> + KVMS390FLICState *flic = tmp->parent; >>>> + struct kvm_s390_ais_all ais; >>>> + struct kvm_device_attr attr = { >>>> + .group = KVM_DEV_FLIC_AISM_ALL, >>>> + .addr = (uint64_t)&ais, >>>> + .attr = sizeof(ais), >>>> + }; >>>> + >>>> + if (ioctl(flic->fd, KVM_GET_DEVICE_ATTR, &attr)) { >>>> + error_report("Failed to retrieve kvm flic ais states"); >>> There's not much else we can do in that case, is there? >>> >> >> I think this is a very good question! The ioctl should not fail >> under any circumstances, but if it does we have a problem. >> >> Carrying on happily (what we do now) means effectively discarding >> ais state. In general just discarding state ain't a good idea. >> >> In particular it might be OK, but the patch should explain that! >> >> Regarding what could/should we do in such a case (instead >> of discarding state and carrying on happily) I don't know, so >> I tend to agree with you regarding 'not much else we can do'. >> >> Adding Dave and Juan. Maybe they can tell. > > I keep meaning to make the pre_save give a return value for failure, > but it hasn't currently got one. Would you accept patches for that? > > You could try something like: > > qemu_file_set_error(migrate_get_current()->to_dst_file, -EINVAL); > > I *think* the migration code should spot that before it finishes > but it might carry on for a little while before it does. I will keep this patch as is, since this is one of the "should not happen" cases.