Re: [PATCH v2 10/23] xen/arm: compile and run xenbus

[Daniel De Graaf <dgdegra@tycho.nsa.gov>]

On 08/07/2012 02:21 PM, Konrad Rzeszutek Wilk wrote:
> On Mon, Aug 06, 2012 at 03:27:13PM +0100, Stefano Stabellini wrote:
>> bind_evtchn_to_irqhandler can legitimately return 0 (irq 0): it is not
>> an error.
>>
>> If Linux is running as an HVM domain and is running as Dom0, use
>> xenstored_local_init to initialize the xenstore page and event channel.
>>
>> Changes in v2:
>>
>> - refactor xenbus_init.
> 
> Thank you. Lets also CC our friend at NSA who has been doing some work
> in that area. Daniel are you OK with this change - will it still make
> PV initial domain with with the MiniOS XenBus driver?
> 
> Thanks.

That case will work, but what this will break is launching the initial domain
with a Xenstore stub domain already running (see below).

>>
>> Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
>> ---
>>  drivers/xen/xenbus/xenbus_comms.c |    2 +-
>>  drivers/xen/xenbus/xenbus_probe.c |   62 +++++++++++++++++++++++++-----------
>>  drivers/xen/xenbus/xenbus_xs.c    |    1 +
>>  3 files changed, 45 insertions(+), 20 deletions(-)
>>
>> diff --git a/drivers/xen/xenbus/xenbus_comms.c b/drivers/xen/xenbus/xenbus_comms.c
>> index 52fe7ad..c5aa55c 100644
>> --- a/drivers/xen/xenbus/xenbus_comms.c
>> +++ b/drivers/xen/xenbus/xenbus_comms.c
>> @@ -224,7 +224,7 @@ int xb_init_comms(void)
>>  		int err;
>>  		err = bind_evtchn_to_irqhandler(xen_store_evtchn, wake_waiting,
>>  						0, "xenbus", &xb_waitq);
>> -		if (err <= 0) {
>> +		if (err < 0) {
>>  			printk(KERN_ERR "XENBUS request irq failed %i\n", err);
>>  			return err;
>>  		}
> 
>> diff --git a/drivers/xen/xenbus/xenbus_probe.c b/drivers/xen/xenbus/xenbus_probe.c
>> index b793723..a67ccc0 100644
>> --- a/drivers/xen/xenbus/xenbus_probe.c
>> +++ b/drivers/xen/xenbus/xenbus_probe.c
>> @@ -719,37 +719,61 @@ static int __init xenstored_local_init(void)
>>  	return err;
>>  }
>>  
>> +enum xenstore_init {
>> +	UNKNOWN,
>> +	PV,
>> +	HVM,
>> +	LOCAL,
>> +};
>>  static int __init xenbus_init(void)
>>  {
>>  	int err = 0;
>> +	enum xenstore_init usage = UNKNOWN;
>> +	uint64_t v = 0;
>>  
>>  	if (!xen_domain())
>>  		return -ENODEV;
>>  
>>  	xenbus_ring_ops_init();
>>  
>> -	if (xen_hvm_domain()) {
>> -		uint64_t v = 0;
>> -		err = hvm_get_parameter(HVM_PARAM_STORE_EVTCHN, &v);
>> -		if (err)
>> -			goto out_error;
>> -		xen_store_evtchn = (int)v;
>> -		err = hvm_get_parameter(HVM_PARAM_STORE_PFN, &v);
>> -		if (err)
>> -			goto out_error;
>> -		xen_store_mfn = (unsigned long)v;
>> -		xen_store_interface = ioremap(xen_store_mfn << PAGE_SHIFT, PAGE_SIZE);
>> -	} else {
>> -		xen_store_evtchn = xen_start_info->store_evtchn;
>> -		xen_store_mfn = xen_start_info->store_mfn;
>> -		if (xen_store_evtchn)
>> -			xenstored_ready = 1;
>> -		else {
>> +	if (xen_pv_domain())
>> +		usage = PV;
>> +	if (xen_hvm_domain())
>> +		usage = HVM;

The above is correct for domUs, and is overridden for dom0s:

>> +	if (xen_hvm_domain() && xen_initial_domain())
>> +		usage = LOCAL;
>> +	if (xen_pv_domain() && !xen_start_info->store_evtchn)
>> +		usage = LOCAL;

Instead of these checks, I think it should just be:

if (!xen_start_info->store_evtchn)
	usage = LOCAL;

Any domain started after xenstore will have store_evtchn set, so if you don't
have this set, you are either going to be running xenstore locally, or will
use the ioctl to change it later (and so should still set up everything as if
it will be running locally).

>> +	if (xen_pv_domain() && xen_start_info->store_evtchn)
>> +		xenstored_ready = 1;

This part can now just be moved unconditionally into case PV.

>> +
>> +	switch (usage) {
>> +		case LOCAL:
>>  			err = xenstored_local_init();
>>  			if (err)
>>  				goto out_error;
>> -		}
>> -		xen_store_interface = mfn_to_virt(xen_store_mfn);
>> +			xen_store_interface = mfn_to_virt(xen_store_mfn);
>> +			break;
>> +		case PV:
>> +			xen_store_evtchn = xen_start_info->store_evtchn;
>> +			xen_store_mfn = xen_start_info->store_mfn;
>> +			xen_store_interface = mfn_to_virt(xen_store_mfn);
>> +			break;
>> +		case HVM:
>> +			err = hvm_get_parameter(HVM_PARAM_STORE_EVTCHN, &v);
>> +			if (err)
>> +				goto out_error;
>> +			xen_store_evtchn = (int)v;
>> +			err = hvm_get_parameter(HVM_PARAM_STORE_PFN, &v);
>> +			if (err)
>> +				goto out_error;
>> +			xen_store_mfn = (unsigned long)v;
>> +			xen_store_interface =
>> +				ioremap(xen_store_mfn << PAGE_SHIFT, PAGE_SIZE);
>> +			break;
>> +		default:
>> +			pr_warn("Xenstore state unknown\n");
>> +			break;
>>  	}
>>  
>>  	/* Initialize the interface to xenstore. */
>> diff --git a/drivers/xen/xenbus/xenbus_xs.c b/drivers/xen/xenbus/xenbus_xs.c
>> index d1c217b..f7feb3d 100644
>> --- a/drivers/xen/xenbus/xenbus_xs.c
>> +++ b/drivers/xen/xenbus/xenbus_xs.c
>> @@ -44,6 +44,7 @@
>>  #include <linux/rwsem.h>
>>  #include <linux/module.h>
>>  #include <linux/mutex.h>
>> +#include <asm/xen/hypervisor.h>
>>  #include <xen/xenbus.h>
>>  #include <xen/xen.h>
>>  #include "xenbus_comms.h"
>> -- 
>> 1.7.2.5


-- 
Daniel De Graaf
National Security Agency