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

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Date:	Fri, 25 Sep 2015 17:00:10 -0400
From:	Boris Ostrovsky <boris.ostrovsky@...cle.com>
To:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
CC:	Vitaly Kuznetsov <vkuznets@...hat.com>,
	xen-devel@...ts.xenproject.org, x86@...nel.org,
	David Vrabel <david.vrabel@...rix.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] xen/pvhvm: add soft reset on kexec/kdump support

On 09/25/2015 03:35 PM, Konrad Rzeszutek Wilk wrote:
> On Fri, Sep 25, 2015 at 03:19:57PM -0400, Boris Ostrovsky wrote:
>> On 09/25/2015 03:01 PM, Konrad Rzeszutek Wilk wrote:
>>> On Fri, Sep 25, 2015 at 01:17:40PM -0400, Boris Ostrovsky wrote:
>>>> On 09/25/2015 12:07 PM, Vitaly Kuznetsov wrote:
>>>>>> 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?
>>>>> Please see my Xen series:
>>>>> http://lists.xenproject.org/archives/html/xen-devel/2015-09/msg00547.html
>>>>> (last 'full' submission).
>>>>>
>>>>> All patches from my 'toolstack-assisted approach to PVHVM guest kexec'
>>>>> are already merged to xen.git (first 10 are already in 'master' and the
>>>>> last one is in 'staging').
>>>>>
>>>> OK, so I was looking at the right tree. Then I don't understand how
>>>> SHUTDOWN_soft_reset would be reached for a non-privileged domain. The only
>>>> path that I see is
>>>>
>>>>      domain_shutdown()
>>>>      {
>>>>          ...
>>>>          if ( is_hardware_domain(d) )
>>>>              hwdom_shutdown(reason);
>>>>          ...
>>>>      }
>>>>
>>>> Is there another path to handle this op?
>>> Yes:
>>>   e1bd9812966de9a16f30a58e7162b80bd6af361b libxc: support XEN_DOMCTL_soft_reset operation
>>> and
>>>   c57e6ebd8c3e490e353e68d96abec1dad01e72f5 (lib)xl: soft reset support
>>>
>>
>> That's toolstack issuing hypercalls from dom0.
>>
>> I am asking about (non-privileged) guest itself calling SCHEDOP_shutdown.
> The hypervisor ends up calling:
> __domain_finalise_shutdown which sends an VIRQ_DOM_EXC to dom0 which
> makes the toolstack do all of those operations.

OK. But the I don't see anyone checking that 'reason' (or 
'shutdown_code') is SHUTDOWN_soft_reset. In other words, the guest can 
do 'xen_reboot(23)' or 'xen_reboot(154)'. Or, it seems, even 
'xen_reboot(SHUTDOWN_reboot)'? The only value it shouldn't be is 
SHUTDOWN_suspend.

-boris

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