From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:48422) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cN20M-00078y-BD for qemu-devel@nongnu.org; Fri, 30 Dec 2016 13:34:15 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cN20J-0000eX-6L for qemu-devel@nongnu.org; Fri, 30 Dec 2016 13:34:14 -0500 Received: from mx1.redhat.com ([209.132.183.28]:51546) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1cN20J-0000eD-0Q for qemu-devel@nongnu.org; Fri, 30 Dec 2016 13:34:11 -0500 Date: Fri, 30 Dec 2016 16:34:07 -0200 From: Eduardo Habkost Message-ID: <20161230183407.GL3441@thinpad.lan.raisama.net> References: <1483108391-199542-1-git-send-email-imammedo@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1483108391-199542-1-git-send-email-imammedo@redhat.com> Subject: Re: [Qemu-devel] [PATCH] pc: fix crash in rtc_set_memory() if initial cpu is marked as hotplugged List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Igor Mammedov Cc: qemu-devel@nongnu.org, pbonzini@redhat.com, mst@redhat.com, armbru@redhat.com, afaerber@suse.de On Fri, Dec 30, 2016 at 03:33:11PM +0100, Igor Mammedov wrote: > 'hotplugged' propperty is meant to be used on migration side when migrating > source with hotplugged devices. > However though it not exacly correct usage of 'hotplugged' property > it's possible to set generic hotplugged property for CPU using > -cpu foo,hotplugged=on > or > -global foo.hotplugged=on > > in this case qemu crashes with following backtrace: > > ... > > because pc_cpu_plug() assumes that hotplugged CPU could appear only after > rtc/fw_cfg are initialized. > Fix crash by replacing assumption with explicit checks of rtc/fw_cfg > and updating them only if they were initialized. > > Signed-off-by: Igor Mammedov > Reported-by: Eduardo Habkost I like how the new code doesn't depend on DeviceState::hotplugged at all. Reviewed-by: Eduardo Habkost But I would like to understand better how the "hotplugged" property is really supposed to be used. I am not aware of any existing case where the user needs to set "hotplugged" directly and it works. > --- > hw/i386/pc.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/hw/i386/pc.c b/hw/i386/pc.c > index f3d7ad4..7b7e126 100644 > --- a/hw/i386/pc.c > +++ b/hw/i386/pc.c > @@ -1810,8 +1810,10 @@ static void pc_cpu_plug(HotplugHandler *hotplug_dev, > > /* increment the number of CPUs */ > pcms->boot_cpus++; > - if (dev->hotplugged) { > + if (pcms->rtc) { > rtc_set_cpus_count(pcms->rtc, pcms->boot_cpus); > + } > + if (pcms->fw_cfg) { > fw_cfg_modify_i16(pcms->fw_cfg, FW_CFG_NB_CPUS, pcms->boot_cpus); > } > > -- > 2.7.4 > -- Eduardo