From mboxrd@z Thu Jan 1 00:00:00 1970 From: Paolo Bonzini Subject: Re: [PATCH 2/2] KVM: Protect device ops->create and list_add with kvm->lock Date: Tue, 9 Aug 2016 15:16:26 +0200 Message-ID: <44eacdbf-5ec2-6b8c-d2cb-4fe09dbf001d@redhat.com> References: <20160809122035.16196-1-christoffer.dall@linaro.org> <20160809122035.16196-3-christoffer.dall@linaro.org> <27023cbf-294f-b316-97ef-8da4e726cc98@redhat.com> <20160809125519.GG9175@cbox> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Cc: kvm@vger.kernel.org, Andre Przywara , =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= , Alexander Graf , borntraeger@de.ibm.com, paulus@ozlabs.org, kvmarm@lists.cs.columbia.edu To: Christoffer Dall Return-path: Received: from mx1.redhat.com ([209.132.183.28]:53504 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932278AbcHINQf (ORCPT ); Tue, 9 Aug 2016 09:16:35 -0400 In-Reply-To: <20160809125519.GG9175@cbox> Sender: kvm-owner@vger.kernel.org List-ID: On 09/08/2016 14:55, Christoffer Dall wrote: > On Tue, Aug 09, 2016 at 02:37:43PM +0200, Paolo Bonzini wrote: >> >> >> On 09/08/2016 14:20, Christoffer Dall wrote: >>> KVM devices were manipulating list data structures without any form of >>> synchronization, and some implementations of the create operations also >>> suffered from a lack of synchronization. >>> >>> Now when we've split the xics create operation into create and init, we >>> can hold the kvm->lock mutex while calling the create operation and when >>> manipulating the devices list. >>> >>> The error path in the generic code gets slightly ugly because we have to >>> take the mutex again and delete the device from the list, but holding >>> the mutex during anon_inode_getfd or releasing/locking the mutex in the >>> common non-error path seemed wrong. >>> >>> Signed-off-by: Christoffer Dall >> >> Very nice (and small), but please add a comment to the create member in >> kvm_device_ops. > > Like this?: > > diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h > index d3c9b82..9c28b4d 100644 > --- a/include/linux/kvm_host.h > +++ b/include/linux/kvm_host.h > @@ -1113,6 +1113,12 @@ struct kvm_device { > /* create, destroy, and name are mandatory */ > struct kvm_device_ops { > const char *name; > + > + /* > + * create is called holding kvm->lock and any operations not suitable > + * to do while holding the lock should be deferred to init (see > + * below). > + */ > int (*create)(struct kvm_device *dev, u32 type); > > /* > That's okay, series Reviewed-by: Paolo Bonzini