From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH 0/2] kvm: disable virtualization on kdump Date: Mon, 27 Oct 2008 10:54:01 +0200 Message-ID: <490581A9.80108@redhat.com> References: <20081022232824.GD5247@verge.net.au> <20081023194129.GD27959@blackpad> <20081023222906.GB10753@verge.net.au> <4904676F.3020706@redhat.com> <490487C1.1010707@redhat.com> <20081026213927.GF23893@blackpad> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: Andrew Morton , kvm-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, kexec-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org, Haren Myneni , Simon Horman , "Eric W. Biederman" , Vivek Goyal To: Eduardo Habkost Return-path: In-Reply-To: <20081026213927.GF23893@blackpad> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: kexec-bounces-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org Errors-To: kexec-bounces+glkk-kexec=m.gmane.org-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org List-Id: kvm.vger.kernel.org Eduardo Habkost wrote: >> (we can use NMI IPIs, but that will likely be messy) >> > > NMI IPIs are already used on x86 native_machine_crash_shutdown(), so > it wouldn't get more messy that it is currently. We just need to add > another bit of code to the code that already runs on an NMI handler. > > That looks like the easiest (and best) way out. > My question is: is a notifier chain too much complexity for a sensible > piece of code like that? If so, a compile-time hook on that point > would be safer, I think an unconditional vmx disable is wanted here, so kexec can work with other hypervisors. > but then it wouldn't work when KVM is compiled as a > out-of-tree module. > The external module can do without. It's possible to hijack the nmi vector, but I don't think that's a good idea. If someone wants kexec+vmx on an older kernel, they can patch that kernel. >> But what happens when the kdump kernel reboots? If it is uniprocessor, >> it will never have a chance to disable vmx on other cpus. Using acpi >> reset (now default) works around this on some machines, but not all. >> > Good point. My problem was a hang when booting the kdump kernel, but it > may also cause problems later, when the kdump kernel reboots. > The hang was likely caused by vmx blocking INIT. Sigh. -- error compiling committee.c: too many arguments to function