Re: libxl: cannot start guest

[Roger Pau Monne <roger.pau@citrix.com>]

Christoph Egger wrote:
> On 05/23/12 12:11, Ian Campbell wrote:
>
>> On Tue, 2012-05-22 at 16:32 +0100, Christoph Egger wrote:
>>> On 05/22/12 17:21, Ian Campbell wrote:
>>>
>>>> On Tue, 2012-05-22 at 16:16 +0100, Christoph Egger wrote:
>>>>> On 05/22/12 16:20, Ian Campbell wrote:
>>>>>> All the>= checks on *xcg_handle seem wrong to me. Really they should be
>>>>>> checking != NULL, since otherwise they don't actually discriminate the
>>>>>> two cases! Does making that change help?
>>>>> Yes, that helps! I can start guests again.
>>>> Excellent, I assume you are going to submit the patch (i.e. I don't need
>>>> to..)
>>> Yes, patch attached.
>> I fixed up the commit message as follows. I'll apply if IanJ agrees or
>> acks it.
>
> Thank you. Ian J. what do you say?
>
> Christoph
>
>
>> 8<-----------------------------
>>
>>  From 6b43ca97f5f8c4fa9bf24101253af21bc66ddf96 Mon Sep 17 00:00:00 2001
>> From: Christoph Egger<Christoph.Egger@amd.com>
>> Date: Tue, 22 May 2012 17:32:21 +0200
>> Subject: [PATCH] xenstore: fix crash on platforms with no gntdev driver implementation.
>>
>> Fix pointer checks introduced in changeset 24757:aae516b78fce.
>>
>> Signed-off-by: Christoph Egger<Christoph.Egger@amd.com>
>> Acked-by: Ian Campbell<ian.campbell@citrix.com>
>> ---
>>   tools/xenstore/xenstored_domain.c |    4 ++--
>>   1 files changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/tools/xenstore/xenstored_domain.c b/tools/xenstore/xenstored_domain.c
>> index f8c822f..bf83d58 100644
>> --- a/tools/xenstore/xenstored_domain.c
>> +++ b/tools/xenstore/xenstored_domain.c
>> @@ -167,7 +167,7 @@ static int readchn(struct connection *conn, void *data, unsigned int len)
>>
>>   static void *map_interface(domid_t domid, unsigned long mfn)
>>   {
>> -	if (*xcg_handle>= 0) {
>> +	if (*xcg_handle != NULL) {
>>   		/* this is the preferred method */
>>   		return xc_gnttab_map_grant_ref(*xcg_handle, domid,
>>   			GNTTAB_RESERVED_XENSTORE, PROT_READ|PROT_WRITE);
>> @@ -179,7 +179,7 @@ static void *map_interface(domid_t domid, unsigned long mfn)
>>
>>   static void unmap_interface(void *interface)
>>   {
>> -	if (*xcg_handle>= 0)
>> +	if (*xcg_handle != NULL)
>>   		xc_gnttab_munmap(*xcg_handle, interface, 1);
>>   	else
>>   		munmap(interface, getpagesize());

I also see an error when starting xencommons on NetBSD:

test# /usr/xen42/etc/rc.d/xencommons onestart
Cleaning xenstore database.
Starting xenservices: xenstored, xenconsoled, xenbackendd.xc: error: 
OSDEP: interface 2 (gnttab) not supported on this platform: Internal error

Which is quite annoying, but I'm not really sure of the most elegant way 
to solve this. The error comes from tools/libxc/xc_private.c:177, so 
maybe just removing that message would be ok, or something like this:

--- a/tools/libxc/xc_private.c
+++ b/tools/libxc/xc_private.c
@@ -265,8 +265,12 @@ int xc_evtchn_close(xc_evtchn *xce)
  xc_gnttab *xc_gnttab_open(xentoollog_logger *logger,
                               unsigned open_flags)
  {
+#ifndef __NetBSD__
      return xc_interface_open_common(logger, NULL, open_flags,
                                      XC_OSDEP_GNTTAB);
+#else
+    return NULL;
+#endif
  }

Which is not really pretty.