[v2,4/7] gnttab: re-arrange struct active_grant_entry

Commit Message

Jan Beulich Aug. 16, 2017, 10:49 a.m. UTC

While benign to 32-bit arches, this shrinks the size from 56 to 48
bytes on 64-bit ones (while still leaving a 16-bit hole).

Take the opportunity and consistently use bool/true/false for all
is_sub_page uses.

Signed-off-by: Jan Beulich <[e-mail]>
---
v2: Re-base and extend to clean up is_sub_page uses at once.

Comments

Andrew Cooper Aug. 16, 2017, 11:29 a.m. UTC | #1

On 16/08/17 11:49, Jan Beulich wrote:
> While benign to 32-bit arches, this shrinks the size from 56 to 48
> bytes on 64-bit ones (while still leaving a 16-bit hole).
>
> Take the opportunity and consistently use bool/true/false for all
> is_sub_page uses.
>
> Signed-off-by: Jan Beulich <[e-mail]>

Reviewed-by: Andrew Cooper <[e-mail]>

Patch

--- a/xen/common/grant_table.c
+++ b/xen/common/grant_table.c
@@ -177,15 +177,15 @@  struct active_grant_entry {
 #define GNTPIN_devr_mask     (0xFFU << GNTPIN_devr_shift)
 
     domid_t       domid;  /* Domain being granted access.             */
-    struct domain *trans_domain;
+    unsigned int  start:15; /* For sub-page grants, the start offset
+                               in the page.                           */
+    bool          is_sub_page:1; /* True if this is a sub-page grant. */
+    unsigned int  length:16; /* For sub-page grants, the length of the
+                                grant.                                */
     grant_ref_t   trans_gref;
+    struct domain *trans_domain;
     unsigned long frame;  /* Frame being granted.                     */
     unsigned long gfn;    /* Guest's idea of the frame being granted. */
-    unsigned      is_sub_page:1; /* True if this is a sub-page grant. */
-    unsigned      start:15; /* For sub-page grants, the start offset
-                               in the page.                           */
-    unsigned      length:16; /* For sub-page grants, the length of the
-                                grant.                                */
     spinlock_t    lock;      /* lock to protect access of this entry.
                                 see docs/misc/grant-tables.txt for
                                 locking protocol                      */
@@ -896,7 +896,7 @@  map_grant_ref(
             act->frame = frame;
             act->start = 0;
             act->length = PAGE_SIZE;
-            act->is_sub_page = 0;
+            act->is_sub_page = false;
             act->trans_domain = rd;
             act->trans_gref = op->ref;
         }
@@ -2164,7 +2164,7 @@  acquire_grant_for_copy(
     unsigned long grant_frame;
     uint16_t trans_page_off;
     uint16_t trans_length;
-    int is_sub_page;
+    bool is_sub_page;
     s16 rc = GNTST_okay;
 
     *page = NULL;
@@ -2293,7 +2293,7 @@  acquire_grant_for_copy(
              * but we always treat it as one because that blocks mappings of
              * transitive grants.
              */
-            act->is_sub_page = 1;
+            act->is_sub_page = true;
         }
     }
     else if ( !old_pin ||
@@ -2314,7 +2314,7 @@  acquire_grant_for_copy(
             if ( rc != GNTST_okay )
                 goto unlock_out_clear;
             act->gfn = gfn;
-            is_sub_page = 0;
+            is_sub_page = false;
             trans_page_off = 0;
             trans_length = PAGE_SIZE;
         }
@@ -2325,7 +2325,7 @@  acquire_grant_for_copy(
             if ( rc != GNTST_okay )
                 goto unlock_out_clear;
             act->gfn = sha2->full_page.frame;
-            is_sub_page = 0;
+            is_sub_page = false;
             trans_page_off = 0;
             trans_length = PAGE_SIZE;
         }
@@ -2336,7 +2336,7 @@  acquire_grant_for_copy(
             if ( rc != GNTST_okay )
                 goto unlock_out_clear;
             act->gfn = sha2->sub_page.frame;
-            is_sub_page = 1;
+            is_sub_page = true;
             trans_page_off = sha2->sub_page.page_off;
             trans_length = sha2->sub_page.length;
         }