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Commit d2fb4c51 authored by Daniel De Graaf's avatar Daniel De Graaf Committed by Konrad Rzeszutek Wilk
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xenbus: Add support for xenbus backend in stub domain 



Add an ioctl to the /dev/xen/xenbus_backend device allowing the xenbus
backend to be started after the kernel has booted. This allows xenstore
to run in a different domain from the dom0.

Signed-off-by: default avatarDaniel De Graaf <dgdegra@tycho.nsa.gov>
Signed-off-by: default avatarKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
parent 2f1bd67d

drivers/xen/xenbus/xenbus_comms.c

+6 −0
Original line number Diff line number Diff line
@@ -234,3 +234,9 @@ int xb_init_comms(void) 


	return 0;

}



void xb_deinit_comms(void)

{

	unbind_from_irqhandler(xenbus_irq, &xb_waitq);

	xenbus_irq = 0;

}

drivers/xen/xenbus/xenbus_comms.h

+1 −0
Original line number Diff line number Diff line
@@ -35,6 +35,7 @@ 


int xs_init(void);

int xb_init_comms(void);

void xb_deinit_comms(void);



/* Low level routines. */

int xb_write(const void *data, unsigned len);

drivers/xen/xenbus/xenbus_dev_backend.c

+51 −0
Original line number Diff line number Diff line
@@ -8,7 +8,11 @@ 


#include <xen/xen.h>

#include <xen/page.h>

#include <xen/xenbus.h>

#include <xen/xenbus_dev.h>

#include <xen/grant_table.h>

#include <xen/events.h>

#include <asm/xen/hypervisor.h>



#include "xenbus_comms.h"
@@ -22,6 +26,50 @@ static int xenbus_backend_open(struct inode *inode, struct file *filp) 
	return nonseekable_open(inode, filp);

}



static long xenbus_alloc(domid_t domid)

{

	struct evtchn_alloc_unbound arg;

	int err = -EEXIST;



	xs_suspend();



	/* If xenstored_ready is nonzero, that means we have already talked to

	 * xenstore and set up watches. These watches will be restored by

	 * xs_resume, but that requires communication over the port established

	 * below that is not visible to anyone until the ioctl returns.

	 *

	 * This can be resolved by splitting the ioctl into two parts

	 * (postponing the resume until xenstored is active) but this is

	 * unnecessarily complex for the intended use where xenstored is only

	 * started once - so return -EEXIST if it's already running.

	 */

	if (xenstored_ready)

		goto out_err;



	gnttab_grant_foreign_access_ref(GNTTAB_RESERVED_XENSTORE, domid,

			virt_to_mfn(xen_store_interface), 0 /* writable */);



	arg.dom = DOMID_SELF;

	arg.remote_dom = domid;



	err = HYPERVISOR_event_channel_op(EVTCHNOP_alloc_unbound, &arg);

	if (err)

		goto out_err;



	if (xen_store_evtchn > 0)

		xb_deinit_comms();



	xen_store_evtchn = arg.port;



	xs_resume();



	return arg.port;



 out_err:

	xs_suspend_cancel();

	return err;

}



static long xenbus_backend_ioctl(struct file *file, unsigned int cmd, unsigned long data)

{

	if (!capable(CAP_SYS_ADMIN))
@@ -33,6 +81,9 @@ static long xenbus_backend_ioctl(struct file *file, unsigned int cmd, unsigned l 
				return xen_store_evtchn;

			return -ENODEV;



		case IOCTL_XENBUS_BACKEND_SETUP:

			return xenbus_alloc(data);



		default:

			return -ENOTTY;

	}

include/xen/grant_table.h

+2 −0
Original line number Diff line number Diff line
@@ -46,6 +46,8 @@ 


#include <xen/features.h>



#define GNTTAB_RESERVED_XENSTORE 1



/* NR_GRANT_FRAMES must be less than or equal to that configured in Xen */

#define NR_GRANT_FRAMES 4

include/xen/xenbus_dev.h

+3 −0
Original line number Diff line number Diff line
@@ -38,4 +38,7 @@ 
#define IOCTL_XENBUS_BACKEND_EVTCHN			\

	_IOC(_IOC_NONE, 'B', 0, 0)



#define IOCTL_XENBUS_BACKEND_SETUP			\

	_IOC(_IOC_NONE, 'B', 1, 0)



#endif /* __LINUX_XEN_XENBUS_DEV_H__ */