[PATCH 3/4] ARM/vgic: Use for_each_set_bit() in gic_find_unused_lr()

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

There are no bits set in lr_mask beyond nr_lrs, so when substituting
bitmap_for_each() for for_each_set_bit(), we don't need to worry about the
upper bound.

However, the type of lr_mask does matter, so switch it to be uint64_t * and
move unsigned long * override until the find_next_zero_bit() call.

Move lr_val into a narrower scope and drop used_lr as it's declared by
for_each_set_bit() itself.

Drop the nr_lrs variable and use gic_get_nr_lrs() in the one location its now
used.  It hides a triple pointer defererence, and while it may not be needed
in the PRISTINE case, it certainly doesn't need to be live across the rest of
the function.

No functional change.

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
CC: Stefano Stabellini <sstabellini@xxxxxxxxxx>
CC: Julien Grall <julien@xxxxxxx>
CC: Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>
CC: Bertrand Marquis <bertrand.marquis@xxxxxxx>
CC: Michal Orzel <michal.orzel@xxxxxxx>

ARM64:

  $ ../scripts/bloat-o-meter xen-syms-arm64-{before,after}
  add/remove: 0/0 grow/shrink: 0/1 up/down: 0/-28 (-28)
  Function                                     old     new   delta
  gic_find_unused_lr.constprop                 228     200     -28

inc -2 find_next_bit()

ARM32:

  $ ../scripts/bloat-o-meter xen-syms-arm32-{before,after}
  add/remove: 0/0 grow/shrink: 1/0 up/down: 48/0 (48)
  Function                                     old     new   delta
  gic_find_unused_lr                           260     308     +48

because uint64_t, but -2 _find_{first,next}_bit_le()
---
 xen/arch/arm/gic-vgic.c | 12 +++++-------
 1 file changed, 5 insertions(+), 7 deletions(-)

diff --git a/xen/arch/arm/gic-vgic.c b/xen/arch/arm/gic-vgic.c
index 3f14aab2efc7..ea48c5375a91 100644
--- a/xen/arch/arm/gic-vgic.c
+++ b/xen/arch/arm/gic-vgic.c
@@ -102,25 +102,23 @@ static unsigned int gic_find_unused_lr(struct vcpu *v,
                                        struct pending_irq *p,
                                        unsigned int lr)
 {
-    unsigned int nr_lrs = gic_get_nr_lrs();
-    unsigned long *lr_mask = (unsigned long *) &this_cpu(lr_mask);
-    struct gic_lr lr_val;
+    uint64_t *lr_mask = &this_cpu(lr_mask);
 
     ASSERT(spin_is_locked(&v->arch.vgic.lock));
 
     if ( unlikely(test_bit(GIC_IRQ_GUEST_PRISTINE_LPI, &p->status)) )
     {
-        unsigned int used_lr;
-
-        bitmap_for_each ( used_lr, lr_mask, nr_lrs )
+        for_each_set_bit ( used_lr, *lr_mask )
         {
+            struct gic_lr lr_val;
+
             gic_hw_ops->read_lr(used_lr, &lr_val);
             if ( lr_val.virq == p->irq )
                 return used_lr;
         }
     }
 
-    lr = find_next_zero_bit(lr_mask, nr_lrs, lr);
+    lr = find_next_zero_bit((unsigned long *)lr_mask, gic_get_nr_lrs(), lr);
 
     return lr;
 }
-- 
2.39.2