[PATCH v2] powerpc/xive: Use cpumask_intersects()

[Costa Shulyupin]

Replace `cpumask_any_and(a, b) >= nr_cpu_ids`
with the more readable `!cpumask_intersects(a, b)`.

Comparison between cpumask_any_and() and cpumask_intersects()

The cpumask_any_and() function expands using FIND_FIRST_BIT(),
resulting in a loop that iterates through each bit of the bitmask:

for (idx = 0; idx * BITS_PER_LONG < sz; idx++) {
        val = (FETCH);
        if (val) {
                sz = min(idx * BITS_PER_LONG + __ffs(MUNGE(val)), sz);
                break;
        }
}

The cpumask_intersects() function expands using __bitmap_intersects(),
resulting in that the first loop iterates through each long word of the bitmask,
and the second through each bit within a long word:

unsigned int k, lim = bits/BITS_PER_LONG;
for (k = 0; k < lim; ++k)
        if (bitmap1[k] & bitmap2[k])
                return true;

if (bits % BITS_PER_LONG)
        if ((bitmap1[k] & bitmap2[k]) & BITMAP_LAST_WORD_MASK(bits))
                return true;

Conclusion: cpumask_intersects() is at least as efficient as cpumask_any_and(),
if not more so, as it typically performs fewer loops and comparisons.

Signed-off-by: Costa Shulyupin <costa.s...@redhat.com>
Reviewed-by: Ming Lei <ming....@redhat.com>

---

v2: add comparison between cpumask_any_and() and cpumask_intersects()

---
 arch/powerpc/sysdev/xive/common.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/powerpc/sysdev/xive/common.c 
b/arch/powerpc/sysdev/xive/common.c
index fa01818c1972c..a6c388bdf5d08 100644
--- a/arch/powerpc/sysdev/xive/common.c
+++ b/arch/powerpc/sysdev/xive/common.c
@@ -726,7 +726,7 @@ static int xive_irq_set_affinity(struct irq_data *d,
        pr_debug("%s: irq %d/0x%x\n", __func__, d->irq, hw_irq);
 
        /* Is this valid ? */
-       if (cpumask_any_and(cpumask, cpu_online_mask) >= nr_cpu_ids)
+       if (!cpumask_intersects(cpumask, cpu_online_mask))
                return -EINVAL;
 
        /*
-- 
2.45.0