Re: [PATCH] xen/pvhvm: add soft reset on kexec/kdump support

From: Boris Ostrovsky
Date: Fri Sep 25 2015 - 11:56:00 EST

On 09/25/2015 09:59 AM, Konrad Rzeszutek Wilk wrote:
On Fri, Sep 25, 2015 at 11:59:52AM +0200, Vitaly Kuznetsov wrote:
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

Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>

with s/pvhvm/hvm/

to match with the rest of the file.

+static void xen_pvhvm_kexec_shutdown(void)
+ native_machine_shutdown();
+ if (kexec_in_progress)
+ xen_reboot(SHUTDOWN_soft_reset);

This routine is not kexec-specific so "kexec_" should be dropped from the name.

Also, I am not sure I see how this new op will be used in the hypervisor --- currently AFAICS it is only processed under is_hardware_domain(). Are there other patches that will support HVM guests?


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