[PATCH for-4.5 v3] x86/hvm: remove stray lock release from hvm_ioreq_server_init()

[Vitaly Kuznetsov <vkuznets@redhat.com>]

If HVM_PARAM_IOREQ_PFN, HVM_PARAM_BUFIOREQ_PFN, or HVM_PARAM_BUFIOREQ_EVTCHN
parameters are read when guest domain is dying it leads to the following
ASSERT:

(XEN) Assertion '_raw_spin_is_locked(lock)' failed at ...workspace/KERNEL/xen/xen/include/asm/spinlock.h:18
(XEN) ----[ Xen-4.5-unstable  x86_64  debug=y  Not tainted ]----
...
(XEN) Xen call trace:
(XEN)    [<ffff82d08012b07f>] _spin_unlock+0x27/0x30
(XEN)    [<ffff82d0801b6103>] hvm_create_ioreq_server+0x3df/0x49a
(XEN)    [<ffff82d0801bcceb>] do_hvm_op+0x12bf/0x27a0
(XEN)    [<ffff82d08022b9bb>] syscall_enter+0xeb/0x145

The root cause of this issue is the fact that ioreq_server.lock is being
released twice - first in hvm_ioreq_server_init() and then in hvm_create_ioreq_server().
Drop the lock release from hvm_ioreq_server_init() as we don't take it here, do minor
label cleanup.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
Changes from v1:
- Instead of protecting agains creating ioreq server while guest domain
  is dying remove stray ioreq_server.lock lock release
  from hvm_ioreq_server_init(). Rename the patch accordingly.
  [Paul Durrant]

Changes from v2:
- Cleanup labels in hvm_ioreq_server_init(), shorten patch name
  [Jan Beulich]
---
 xen/arch/x86/hvm/hvm.c | 12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index 0a20cbe..94c58e1 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -970,30 +970,28 @@ static int hvm_ioreq_server_init(struct hvm_ioreq_server *s, struct domain *d,
 
     rc = hvm_ioreq_server_alloc_rangesets(s, is_default);
     if ( rc )
-        goto fail1;
+        return rc;
 
     rc = hvm_ioreq_server_map_pages(s, is_default, handle_bufioreq);
     if ( rc )
-        goto fail2;
+        goto fail_map;
 
     for_each_vcpu ( d, v )
     {
         rc = hvm_ioreq_server_add_vcpu(s, is_default, v);
         if ( rc )
-            goto fail3;
+            goto fail_add;
     }
 
     return 0;
 
- fail3:
+ fail_add:
     hvm_ioreq_server_remove_all_vcpus(s);
     hvm_ioreq_server_unmap_pages(s, is_default);
 
- fail2:
+ fail_map:
     hvm_ioreq_server_free_rangesets(s, is_default);
 
- fail1:
-    spin_unlock(&d->arch.hvm_domain.ioreq_server.lock);
     return rc;
 }
 
-- 
1.9.3