Re: Patch "x86/xen: Support kexec/kdump in HVM guests by doing a soft reset" has been added to the 4.2-stable tree

[Greg KH <gregkh@linuxfoundation.org>]

On Wed, Oct 14, 2015 at 04:20:16PM +0100, David Vrabel wrote:
> On 13/10/15 23:59, gregkh@linuxfoundation.org wrote:
> > 
> > This is a note to let you know that I've just added the patch titled
> > 
> >     x86/xen: Support kexec/kdump in HVM guests by doing a soft reset
> > 
> > to the 4.2-stable tree which can be found at:
> >     http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
> > 
> > The filename of the patch is:
> >      x86-xen-support-kexec-kdump-in-hvm-guests-by-doing-a-soft-reset.patch
> > and it can be found in the queue-4.2 subdirectory.
> > 
> > If you, or anyone else, feels it should not be added to the stable tree,
> > please let <stable@vger.kernel.org> know about it.
> > 
> > 
> > From 0b34a166f291d255755be46e43ed5497cdd194f2 Mon Sep 17 00:00:00 2001
> > From: Vitaly Kuznetsov <vkuznets@redhat.com>
> > Date: Fri, 25 Sep 2015 11:59:52 +0200
> > Subject: x86/xen: Support kexec/kdump in HVM guests by doing a soft reset
> > 
> > From: Vitaly Kuznetsov <vkuznets@redhat.com>
> > 
> > commit 0b34a166f291d255755be46e43ed5497cdd194f2 upstream.
> > 
> > Currently there is a number of issues preventing PVHVM Xen guests from
> > doing successful kexec/kdump:
> > 
> >   - Bound event channels.
> >   - Registered vcpu_info.
> >   - PIRQ/emuirq mappings.
> >   - shared_info frame after XENMAPSPACE_shared_info operation.
> >   - Active grant mappings.
> > 
> > Basically, newly booted kernel stumbles upon already set up Xen
> > interfaces and there is no way to reestablish them. In Xen-4.7 a new
> > feature called 'soft reset' is coming. A guest performing kexec/kdump
> > operation is supposed to call SCHEDOP_shutdown hypercall with
> > SHUTDOWN_soft_reset reason before jumping to new kernel. Hypervisor
> > (with some help from toolstack) will do full domain cleanup (but
> > keeping its memory and vCPU contexts intact) returning the guest to
> > the state it had when it was first booted and thus allowing it to
> > start over.
> > 
> > Doing SHUTDOWN_soft_reset on Xen hypervisors which don't support it is
> > probably OK as by default all unknown shutdown reasons cause domain
> > destroy with a message in toolstack log: 'Unknown shutdown reason code
> > 5. Destroying domain.'  which gives a clue to what the problem is and
> > eliminates false expectations.
> [...]
> > --- a/arch/x86/xen/enlighten.c
> > +++ b/arch/x86/xen/enlighten.c
> > @@ -33,6 +33,10 @@
> >  #include <linux/memblock.h>
> >  #include <linux/edd.h>
> >  
> > +#ifdef CONFIG_KEXEC_CORE
> > +#include <linux/kexec.h>
> > +#endif
> > +
> >  #include <xen/xen.h>
> >  #include <xen/events.h>
> >  #include <xen/interface/xen.h>
> > @@ -1800,6 +1804,21 @@ static struct notifier_block xen_hvm_cpu
> >  	.notifier_call	= xen_hvm_cpu_notify,
> >  };
> >  
> > +#ifdef CONFIG_KEXEC_CORE
> 
> This should be CONFIG_KEXEC in 4.2 and earlier, CONFIG_EXEC_CORE was
> introduced in 4.3.
> 
> Do you want an updated patch?

An updated patch would be great, thanks.