[PATCH v3] ARM/vgic: Use for_each_set_bit() in vgic-mmio*

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

These are all loops over a scalar value, and don't need to call general bitop
helpers behind the scenes.

Clamp data to the width of the access in dispatch_mmio_write(), rather than
doing so in every handler.

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>

v3:
 * Split out of series.
 * Move clamping to common location.

Bloat-o-meter analysis.  The negative change in each handler also includes the
removal of calls to _find_{first,next}_bit_le(), so the improvement is better
than the summary suggests.

$ ../scripts/bloat-o-meter xen-syms-arm32-{before,after}
add/remove: 0/0 grow/shrink: 1/6 up/down: 24/-156 (-132)
Function                                     old     new   delta
dispatch_mmio_write                          212     236     +24
vgic_mmio_write_spending                     392     368     -24
vgic_mmio_write_senable                      324     300     -24
vgic_mmio_write_cenable                      320     296     -24
vgic_mmio_write_sactive                      204     176     -28
vgic_mmio_write_cpending                     464     436     -28
vgic_mmio_write_cactive                      204     176     -28

$ ../scripts/bloat-o-meter xen-syms-arm64-{before,after}
add/remove: 0/0 grow/shrink: 1/6 up/down: 32/-196 (-164)
Function                                     old     new   delta
dispatch_mmio_write                          164     196     +32
vgic_mmio_write_spending                     320     312      -8
vgic_mmio_write_cpending                     368     356     -12
vgic_mmio_write_sactive                      192     156     -36
vgic_mmio_write_cactive                      192     156     -36
vgic_mmio_write_cenable                      316     268     -48
vgic_mmio_write_senable                      320     264     -56
---
 xen/arch/arm/vgic/vgic-mmio.c | 22 ++++++++++------------
 1 file changed, 10 insertions(+), 12 deletions(-)

diff --git a/xen/arch/arm/vgic/vgic-mmio.c b/xen/arch/arm/vgic/vgic-mmio.c
index 4ad350c21c8b..b4ba34cfc368 100644
--- a/xen/arch/arm/vgic/vgic-mmio.c
+++ b/xen/arch/arm/vgic/vgic-mmio.c
@@ -70,9 +70,8 @@ void vgic_mmio_write_senable(struct vcpu *vcpu,
                              unsigned long val)
 {
     uint32_t intid = VGIC_ADDR_TO_INTID(addr, 1);
-    unsigned int i;
 
-    bitmap_for_each ( i, &val, len * 8 )
+    for_each_set_bit ( i, val )
     {
         struct vgic_irq *irq = vgic_get_irq(vcpu->domain, vcpu, intid + i);
         unsigned long flags;
@@ -115,9 +114,8 @@ void vgic_mmio_write_cenable(struct vcpu *vcpu,
                              unsigned long val)
 {
     uint32_t intid = VGIC_ADDR_TO_INTID(addr, 1);
-    unsigned int i;
 
-    bitmap_for_each ( i, &val, len * 8 )
+    for_each_set_bit ( i, val )
     {
         struct vgic_irq *irq;
         unsigned long flags;
@@ -183,11 +181,10 @@ void vgic_mmio_write_spending(struct vcpu *vcpu,
                               unsigned long val)
 {
     uint32_t intid = VGIC_ADDR_TO_INTID(addr, 1);
-    unsigned int i;
     unsigned long flags;
     irq_desc_t *desc;
 
-    bitmap_for_each ( i, &val, len * 8 )
+    for_each_set_bit ( i, val )
     {
         struct vgic_irq *irq = vgic_get_irq(vcpu->domain, vcpu, intid + i);
 
@@ -231,11 +228,10 @@ void vgic_mmio_write_cpending(struct vcpu *vcpu,
                               unsigned long val)
 {
     uint32_t intid = VGIC_ADDR_TO_INTID(addr, 1);
-    unsigned int i;
     unsigned long flags;
     irq_desc_t *desc;
 
-    bitmap_for_each ( i, &val, len * 8 )
+    for_each_set_bit ( i, val )
     {
         struct vgic_irq *irq = vgic_get_irq(vcpu->domain, vcpu, intid + i);
 
@@ -327,9 +323,8 @@ void vgic_mmio_write_cactive(struct vcpu *vcpu,
                              unsigned long val)
 {
     uint32_t intid = VGIC_ADDR_TO_INTID(addr, 1);
-    unsigned int i;
 
-    bitmap_for_each ( i, &val, len * 8 )
+    for_each_set_bit ( i, val )
     {
         struct vgic_irq *irq = vgic_get_irq(vcpu->domain, vcpu, intid + i);
 
@@ -357,9 +352,8 @@ void vgic_mmio_write_sactive(struct vcpu *vcpu,
                              unsigned long val)
 {
     uint32_t intid = VGIC_ADDR_TO_INTID(addr, 1);
-    unsigned int i;
 
-    bitmap_for_each ( i, &val, len * 8 )
+    for_each_set_bit ( i, val )
     {
         struct vgic_irq *irq = vgic_get_irq(vcpu->domain, vcpu, intid + i);
 
@@ -591,6 +585,10 @@ static int dispatch_mmio_write(struct vcpu *vcpu, 
mmio_info_t *info,
     if ( !region )
         return 0;
 
+    /* Clamp data to the width of the access. */
+    if ( len < sizeof(data) )
+        data &= (1UL << (len * 8)) - 1;
+
     switch (iodev->iodev_type)
     {
     case IODEV_DIST:
-- 
2.39.5