x86/mem_sharing: cleanup code and comments in various locations

No functional changes.

Signed-off-by: Tamas K Lengyel <tamas.lengyel@intel.com>
Acked-by: Andrew Cooper <andrew.cooper3@citrix.com>
[Further cleanup]
Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>

xen/arch/x86/hvm/hvm.c

@@ -1884,7 +1884,7 @@ int hvm_hap_nested_page_fault(paddr_t gpa, unsigned long gla,
      * If this GFN is emulated MMIO or marked as read-only, pass the fault
      * to the mmio handler.
      */
-    if ( (p2mt == p2m_mmio_dm) || 
+    if ( (p2mt == p2m_mmio_dm) ||
          (npfec.write_access &&
           (p2m_is_discard_write(p2mt) || (p2mt == p2m_ioreq_server))) )
     {
@@ -1902,12 +1902,11 @@ int hvm_hap_nested_page_fault(paddr_t gpa, unsigned long gla,
     if ( npfec.write_access && (p2mt == p2m_ram_shared) )
     {
         ASSERT(p2m_is_hostp2m(p2m));
-        sharing_enomem = 
-            (mem_sharing_unshare_page(currd, gfn, 0) < 0);
+        sharing_enomem = mem_sharing_unshare_page(currd, gfn, 0);
         rc = 1;
         goto out_put_gfn;
     }
- 
+
     /* Spurious fault? PoD and log-dirty also take this path. */
     if ( p2m_is_ram(p2mt) )
     {
@@ -1953,9 +1952,11 @@ int hvm_hap_nested_page_fault(paddr_t gpa, unsigned long gla,
         __put_gfn(p2m, gfn);
     __put_gfn(hostp2m, gfn);
  out:
-    /* All of these are delayed until we exit, since we might 
+    /*
+     * All of these are delayed until we exit, since we might
      * sleep on event ring wait queues, and we must not hold
-     * locks in such circumstance */
+     * locks in such circumstance.
+     */
     if ( paged )
         p2m_mem_paging_populate(currd, gfn);
     if ( sharing_enomem )

xen/arch/x86/mm/p2m.c

@@ -511,8 +511,10 @@ mfn_t __get_gfn_type_access(struct p2m_domain *p2m, unsigned long gfn_l,
     if ( (q & P2M_UNSHARE) && p2m_is_shared(*t) )
     {
         ASSERT(p2m_is_hostp2m(p2m));
-        /* Try to unshare. If we fail, communicate ENOMEM without
-         * sleeping. */
+        /*
+         * Try to unshare. If we fail, communicate ENOMEM without
+         * sleeping.
+         */
         if ( mem_sharing_unshare_page(p2m->domain, gfn_l, 0) < 0 )
             mem_sharing_notify_enomem(p2m->domain, gfn_l, false);
         mfn = p2m->get_entry(p2m, gfn, t, a, q, page_order, NULL);
@@ -892,15 +894,15 @@ guest_physmap_add_entry(struct domain *d, gfn_t gfn, mfn_t mfn,
                               &a, 0, NULL, NULL);
         if ( p2m_is_shared(ot) )
         {
-            /* Do an unshare to cleanly take care of all corner 
-             * cases. */
+            /* Do an unshare to cleanly take care of all corner cases. */
             int rc;
             rc = mem_sharing_unshare_page(p2m->domain,
                                           gfn_x(gfn_add(gfn, i)), 0);
             if ( rc )
             {
                 p2m_unlock(p2m);
-                /* NOTE: Should a guest domain bring this upon itself,
+                /*
+                 * NOTE: Should a guest domain bring this upon itself,
                  * there is not a whole lot we can do. We are buried
                  * deep in locks from most code paths by now. So, fail
                  * the call and don't try to sleep on a wait queue
@@ -909,8 +911,9 @@ guest_physmap_add_entry(struct domain *d, gfn_t gfn, mfn_t mfn,
                  * However, all current (changeset 3432abcf9380) code
                  * paths avoid this unsavoury situation. For now.
                  *
-                 * Foreign domains are okay to place an event as they 
-                 * won't go to sleep. */
+                 * Foreign domains are okay to place an event as they
+                 * won't go to sleep.
+                 */
                 (void)mem_sharing_notify_enomem(p2m->domain,
                                                 gfn_x(gfn_add(gfn, i)), false);
                 return rc;

xen/include/asm-x86/mem_sharing.h

@@ -33,12 +33,14 @@
 #define MEM_SHARING_AUDIT 0
 #endif
 
-typedef uint64_t shr_handle_t; 
+typedef uint64_t shr_handle_t;
 
 typedef struct rmap_hashtab {
     struct list_head *bucket;
-    /* Overlaps with prev pointer of list_head in union below.
-     * Unlike the prev pointer, this can be NULL. */
+    /*
+     * Overlaps with prev pointer of list_head in union below.
+     * Unlike the prev pointer, this can be NULL.
+     */
     void *flag;
 } rmap_hashtab_t;
 
@@ -57,34 +59,33 @@ struct page_sharing_info
     };
 };
 
-#define sharing_supported(_d) \
-    (is_hvm_domain(_d) && paging_mode_hap(_d)) 
-
 unsigned int mem_sharing_get_nr_saved_mfns(void);
 unsigned int mem_sharing_get_nr_shared_mfns(void);
 
 #define MEM_SHARING_DESTROY_GFN       (1<<1)
 /* Only fails with -ENOMEM. Enforce it with a BUG_ON wrapper. */
 int __mem_sharing_unshare_page(struct domain *d,
-                             unsigned long gfn, 
-                             uint16_t flags);
+                               unsigned long gfn,
+                               uint16_t flags);
+
 static inline int mem_sharing_unshare_page(struct domain *d,
                                            unsigned long gfn,
                                            uint16_t flags)
 {
     int rc = __mem_sharing_unshare_page(d, gfn, flags);
-    BUG_ON( rc && (rc != -ENOMEM) );
+    BUG_ON(rc && (rc != -ENOMEM));
     return rc;
 }
 
-/* If called by a foreign domain, possible errors are
+/*
+ * If called by a foreign domain, possible errors are
  *   -EBUSY -> ring full
  *   -ENOSYS -> no ring to begin with
  * and the foreign mapper is responsible for retrying.
  *
- * If called by the guest vcpu itself and allow_sleep is set, may 
- * sleep on a wait queue, so the caller is responsible for not 
- * holding locks on entry. It may only fail with ENOSYS 
+ * If called by the guest vcpu itself and allow_sleep is set, may
+ * sleep on a wait queue, so the caller is responsible for not
+ * holding locks on entry. It may only fail with ENOSYS
  *
  * If called by the guest vcpu itself and allow_sleep is not set,
  * then it's the same as a foreign domain.
@@ -92,10 +93,11 @@ static inline int mem_sharing_unshare_page(struct domain *d,
 int mem_sharing_notify_enomem(struct domain *d, unsigned long gfn,
                               bool allow_sleep);
 int mem_sharing_memop(XEN_GUEST_HANDLE_PARAM(xen_mem_sharing_op_t) arg);
-int mem_sharing_domctl(struct domain *d, 
+int mem_sharing_domctl(struct domain *d,
                        struct xen_domctl_mem_sharing_op *mec);
 
-/* Scans the p2m and relinquishes any shared pages, destroying 
+/*
+ * Scans the p2m and relinquishes any shared pages, destroying
  * those for which this domain holds the final reference.
  * Preemptible.
  */
@@ -107,19 +109,21 @@ static inline unsigned int mem_sharing_get_nr_saved_mfns(void)
 {
     return 0;
 }
+
 static inline unsigned int mem_sharing_get_nr_shared_mfns(void)
 {
     return 0;
 }
-static inline int mem_sharing_unshare_page(struct domain *d,
-                                           unsigned long gfn,
+
+static inline int mem_sharing_unshare_page(struct domain *d, unsigned long gfn,
                                            uint16_t flags)
 {
     ASSERT_UNREACHABLE();
     return -EOPNOTSUPP;
 }
+
 static inline int mem_sharing_notify_enomem(struct domain *d, unsigned long gfn,
-                              bool allow_sleep)
+                                            bool allow_sleep)
 {
     ASSERT_UNREACHABLE();
     return -EOPNOTSUPP;