[RFC PATCH 3/3] xen/spinlock: support higher number of cpus

[Juergen Gross <jgross@xxxxxxxx>]

There is no real reason why the cpu fields of struct spinlock should
be limited to 12 bits, now that there is a 2 byte padding hole after
those fields.

Make the related structures a little bit larger allowing 16 bits per
cpu number, which is the limit imposed by spinlock_tickets_t.

Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
---
 xen/common/spinlock.c      |  1 +
 xen/include/xen/spinlock.h | 18 +++++++++---------
 2 files changed, 10 insertions(+), 9 deletions(-)

diff --git a/xen/common/spinlock.c b/xen/common/spinlock.c
index a48ed17ac6..5509e4b79a 100644
--- a/xen/common/spinlock.c
+++ b/xen/common/spinlock.c
@@ -303,6 +303,7 @@ int _spin_trylock_recursive(struct spinlock_recursive *lock)
 
     /* Don't allow overflow of recurse_cpu field. */
     BUILD_BUG_ON(NR_CPUS > SPINLOCK_NO_CPU);
+    BUILD_BUG_ON(SPINLOCK_CPU_BITS > sizeof(lock->recurse_cpu) * 8);
     BUILD_BUG_ON(SPINLOCK_RECURSE_BITS < 3);
 
     check_lock(&lock->lock.debug, true);
diff --git a/xen/include/xen/spinlock.h b/xen/include/xen/spinlock.h
index d0cfb4c524..e157b12f6e 100644
--- a/xen/include/xen/spinlock.h
+++ b/xen/include/xen/spinlock.h
@@ -6,16 +6,16 @@
 #include <asm/spinlock.h>
 #include <asm/types.h>
 
-#define SPINLOCK_CPU_BITS  12
+#define SPINLOCK_CPU_BITS  16
 
 #ifdef CONFIG_DEBUG_LOCKS
 union lock_debug {
-    uint16_t val;
-#define LOCK_DEBUG_INITVAL 0xffff
+    uint32_t val;
+#define LOCK_DEBUG_INITVAL 0xffffffff
     struct {
-        uint16_t cpu:SPINLOCK_CPU_BITS;
-#define LOCK_DEBUG_PAD_BITS (14 - SPINLOCK_CPU_BITS)
-        uint16_t :LOCK_DEBUG_PAD_BITS;
+        uint32_t cpu:SPINLOCK_CPU_BITS;
+#define LOCK_DEBUG_PAD_BITS (30 - SPINLOCK_CPU_BITS)
+        uint32_t :LOCK_DEBUG_PAD_BITS;
         bool irq_safe:1;
         bool unseen:1;
     };
@@ -173,10 +173,10 @@ typedef struct spinlock {
 
 struct spinlock_recursive {
     struct spinlock lock;
-    u16 recurse_cpu:SPINLOCK_CPU_BITS;
+    uint16_t recurse_cpu;
 #define SPINLOCK_NO_CPU        ((1u << SPINLOCK_CPU_BITS) - 1)
-#define SPINLOCK_RECURSE_BITS  (16 - SPINLOCK_CPU_BITS)
-    u16 recurse_cnt:SPINLOCK_RECURSE_BITS;
+#define SPINLOCK_RECURSE_BITS  8
+    uint8_t recurse_cnt;
 #define SPINLOCK_MAX_RECURSE   ((1u << SPINLOCK_RECURSE_BITS) - 1)
 };
 
-- 
2.35.3