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[Xen-changelog] [xen master] x86/hvm: take a reference on ioreq server emulating domain



commit ccb42e0ca661e9d2259439504d8b508d42955f4d
Author:     Paul Durrant <paul.durrant@xxxxxxxxxx>
AuthorDate: Tue Mar 20 18:05:23 2018 +0000
Commit:     Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CommitDate: Wed Mar 21 18:24:50 2018 +0000

    x86/hvm: take a reference on ioreq server emulating domain
    
    When an ioreq server is created the code currently stores the id
    of the emulating domain, but does not take a reference on that domain.
    
    This patch modifies the code to hold a reference for the lifetime of the
    ioreq server.
    
    NOTE: ioreq servers are either destroyed explicitly or destroyed implicitly
          in context of XEN_DOMCTL_destroydomain.
          If the emulating domain is shut down prior to the target then the
          any domain reference held by an ioreq server will prevent it from
          being destroyed. However, if an emulating domain is shut down prior
          to its target then it is likely that the target's vcpus will block
          fairly quickly waiting for emulation that will never occur, and when
          the target domain is destroyed the reference on the zombie emulating
          domain will be dropped allowing both to be cleaned up.
    
    Signed-off-by: Paul Durrant <paul.durrant@xxxxxxxxxx>
    Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
 xen/arch/x86/hvm/ioreq.c         | 31 +++++++++++++++++++------------
 xen/include/asm-x86/hvm/domain.h |  4 +---
 2 files changed, 20 insertions(+), 15 deletions(-)

diff --git a/xen/arch/x86/hvm/ioreq.c b/xen/arch/x86/hvm/ioreq.c
index 2b9e5562dd..154f6f1a32 100644
--- a/xen/arch/x86/hvm/ioreq.c
+++ b/xen/arch/x86/hvm/ioreq.c
@@ -218,7 +218,7 @@ static void hvm_unmap_ioreq_page(struct hvm_ioreq_server 
*s, bool buf)
 static int hvm_map_ioreq_page(
     struct hvm_ioreq_server *s, bool buf, unsigned long gfn)
 {
-    struct domain *d = s->domain;
+    struct domain *d = s->target;
     struct hvm_ioreq_page *iorp = buf ? &s->bufioreq : &s->ioreq;
     struct page_info *page;
     void *va;
@@ -315,8 +315,8 @@ static int hvm_ioreq_server_add_vcpu(struct 
hvm_ioreq_server *s,
 
     spin_lock(&s->lock);
 
-    rc = alloc_unbound_xen_event_channel(v->domain, v->vcpu_id, s->domid,
-                                         NULL);
+    rc = alloc_unbound_xen_event_channel(v->domain, v->vcpu_id,
+                                         s->emulator->domain_id, NULL);
     if ( rc < 0 )
         goto fail2;
 
@@ -324,9 +324,10 @@ static int hvm_ioreq_server_add_vcpu(struct 
hvm_ioreq_server *s,
 
     if ( v->vcpu_id == 0 && s->bufioreq.va != NULL )
     {
-        struct domain *d = s->domain;
+        struct domain *d = s->target;
 
-        rc = alloc_unbound_xen_event_channel(v->domain, 0, s->domid, NULL);
+        rc = alloc_unbound_xen_event_channel(v->domain, 0,
+                                             s->emulator->domain_id, NULL);
         if ( rc < 0 )
             goto fail3;
 
@@ -434,7 +435,7 @@ static int hvm_ioreq_server_setup_pages(struct 
hvm_ioreq_server *s,
                                         bool is_default,
                                         bool handle_bufioreq)
 {
-    struct domain *d = s->domain;
+    struct domain *d = s->target;
     unsigned long ioreq_gfn = gfn_x(INVALID_GFN);
     unsigned long bufioreq_gfn = gfn_x(INVALID_GFN);
     int rc;
@@ -471,7 +472,7 @@ static int hvm_ioreq_server_setup_pages(struct 
hvm_ioreq_server *s,
 static void hvm_ioreq_server_unmap_pages(struct hvm_ioreq_server *s,
                                          bool is_default)
 {
-    struct domain *d = s->domain;
+    struct domain *d = s->target;
     bool handle_bufioreq = !!s->bufioreq.va;
 
     if ( handle_bufioreq )
@@ -521,7 +522,7 @@ static int hvm_ioreq_server_alloc_rangesets(struct 
hvm_ioreq_server *s,
         if ( rc )
             goto fail;
 
-        s->range[i] = rangeset_new(s->domain, name,
+        s->range[i] = rangeset_new(s->target, name,
                                    RANGESETF_prettyprint_hex);
 
         xfree(name);
@@ -545,7 +546,7 @@ static int hvm_ioreq_server_alloc_rangesets(struct 
hvm_ioreq_server *s,
 static void hvm_ioreq_server_enable(struct hvm_ioreq_server *s,
                                     bool is_default)
 {
-    struct domain *d = s->domain;
+    struct domain *d = s->target;
     struct hvm_ioreq_vcpu *sv;
     bool handle_bufioreq = !!s->bufioreq.va;
 
@@ -576,7 +577,7 @@ static void hvm_ioreq_server_enable(struct hvm_ioreq_server 
*s,
 static void hvm_ioreq_server_disable(struct hvm_ioreq_server *s,
                                      bool is_default)
 {
-    struct domain *d = s->domain;
+    struct domain *d = s->target;
     bool handle_bufioreq = !!s->bufioreq.va;
 
     spin_lock(&s->lock);
@@ -602,12 +603,15 @@ static int hvm_ioreq_server_init(struct hvm_ioreq_server 
*s,
                                  struct domain *d, bool is_default,
                                  int bufioreq_handling, ioservid_t id)
 {
+    struct domain *currd = current->domain;
     struct vcpu *v;
     int rc;
 
     s->id = id;
-    s->domain = d;
-    s->domid = current->domain->domain_id;
+    s->target = d;
+
+    get_knownalive_domain(currd);
+    s->emulator = currd;
 
     spin_lock_init(&s->lock);
     INIT_LIST_HEAD(&s->ioreq_vcpu_list);
@@ -641,6 +645,7 @@ static int hvm_ioreq_server_init(struct hvm_ioreq_server *s,
  fail_map:
     hvm_ioreq_server_free_rangesets(s, is_default);
 
+    put_domain(s->emulator);
     return rc;
 }
 
@@ -651,6 +656,8 @@ static void hvm_ioreq_server_deinit(struct hvm_ioreq_server 
*s,
     hvm_ioreq_server_remove_all_vcpus(s);
     hvm_ioreq_server_unmap_pages(s, is_default);
     hvm_ioreq_server_free_rangesets(s, is_default);
+
+    put_domain(s->emulator);
 }
 
 static ioservid_t next_ioservid(struct domain *d)
diff --git a/xen/include/asm-x86/hvm/domain.h b/xen/include/asm-x86/hvm/domain.h
index 7f128c05ff..6e03d024c8 100644
--- a/xen/include/asm-x86/hvm/domain.h
+++ b/xen/include/asm-x86/hvm/domain.h
@@ -53,13 +53,11 @@ struct hvm_ioreq_vcpu {
 
 struct hvm_ioreq_server {
     struct list_head       list_entry;
-    struct domain          *domain;
+    struct domain          *target, *emulator;
 
     /* Lock to serialize toolstack modifications */
     spinlock_t             lock;
 
-    /* Domain id of emulating domain */
-    domid_t                domid;
     ioservid_t             id;
     struct hvm_ioreq_page  ioreq;
     struct list_head       ioreq_vcpu_list;
--
generated by git-patchbot for /home/xen/git/xen.git#master

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