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

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Date:	Fri, 25 Sep 2015 15:35:41 -0400
From:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:	Boris Ostrovsky <boris.ostrovsky@...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 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.

> 
> -boris
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