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

[David Vrabel <david.vrabel@citrix.com>]

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?

David