linux-kernel - RE: [PATCH] xenbus: advertize control feature flags

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Date:   Mon, 10 Oct 2016 09:28:51 +0000
From:   Paul Durrant <Paul.Durrant@...rix.com>
To:     Juergen Gross <jgross@...e.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "xen-devel@...ts.xenproject.org" <xen-devel@...ts.xenproject.org>
CC:     Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        David Vrabel <david.vrabel@...rix.com>
Subject: RE: [PATCH] xenbus: advertize control feature flags

> -----Original Message-----
> From: Juergen Gross [mailto:jgross@...e.com]
> Sent: 10 October 2016 10:17
> To: Paul Durrant <Paul.Durrant@...rix.com>; linux-kernel@...r.kernel.org;
> xen-devel@...ts.xenproject.org
> Cc: Boris Ostrovsky <boris.ostrovsky@...cle.com>; David Vrabel
> <david.vrabel@...rix.com>
> Subject: Re: [PATCH] xenbus: advertize control feature flags
> 
> On 10/10/16 09:43, Paul Durrant wrote:
> > The Xen docs specify several flags which a guest can set to advertize
> > which values of the xenstore control/shutdown key it will recognize.
> > This patch adds code to write all the relevant feature-flag keys.
> >
> > Signed-off-by: Paul Durrant <paul.durrant@...rix.com>
> > Cc: Boris Ostrovsky <boris.ostrovsky@...cle.com>
> > Cc: David Vrabel <david.vrabel@...rix.com>
> > Cc: Juergen Gross <jgross@...e.com>
> > ---
> >  drivers/xen/manage.c | 45 +++++++++++++++++++++++++++++++++++--
> --------
> >  1 file changed, 35 insertions(+), 10 deletions(-)
> >
> > diff --git a/drivers/xen/manage.c b/drivers/xen/manage.c
> > index e12bd36..86cf57c 100644
> > --- a/drivers/xen/manage.c
> > +++ b/drivers/xen/manage.c
> 
> > @@ -309,8 +311,31 @@ static struct notifier_block xen_reboot_nb = {
> >
> >  static int setup_shutdown_watcher(void)
> >  {
> > +	static struct shutdown_handler *handler;
> >  	int err;
> >
> > +	for (handler = &shutdown_handlers[0]; handler->command;
> handler++) {
> > +		const char *fmt = "feature-%s";
> > +		int size;
> > +		char *node;
> > +
> > +		if (!handler->flag)
> > +			continue;
> > +
> > +		size = snprintf(NULL, 0, fmt, handler->command);
> > +
> > +		node = kmalloc(++size, GFP_KERNEL);
> > +		if (!node) {
> > +			pr_err("Failed to allocate feature flag\n");
> > +			return -ENOMEM;
> > +		}
> > +
> > +		(void) snprintf(node, size, fmt, handler->command);
> 
> One other nit: please us kasprintf() instead of open coding it.
> 

Yes, that would be better.

Cheers,

  Paul

> 
> Juergen