[PATCH] irqchip/gic-v3-its: Align PCI Multi-MSI allocation on their size

[Ard Biesheuvel]

From: Marc Zyngier <marc.zyng...@arm.com>

Commit 8208d1708b88b412ca97f50a6d951242c88cbbac upstream.

The way we allocate events works fine in most cases, except
when multiple PCI devices share an ITS-visible DevID, and that
one of them is trying to use MultiMSI allocation.

In that case, our allocation is not guaranteed to be zero-based
anymore, and we have to make sure we allocate it on a boundary
that is compatible with the PCI Multi-MSI constraints.

Fix this by allocating the full region upfront instead of iterating
over the number of MSIs. MSI-X are always allocated one by one,
so this shouldn't change anything on that front.

Fixes: b48ac83d6bbc2 ("irqchip: GICv3: ITS: MSI support")
Cc: <sta...@vger.kernel.org> # v4.4 - v4.9
Reported-by: Ard Biesheuvel <ard.biesheu...@linaro.org>
Tested-by: Ard Biesheuvel <ard.biesheu...@linaro.org>
Signed-off-by: Marc Zyngier <marc.zyng...@arm.com>
[ardb: rebased onto v4.9.153, should apply cleanly onto v4.4.y as well]
Signed-off-by: Ard Biesheuvel <ard.biesheu...@linaro.org>
---
 drivers/irqchip/irq-gic-v3-its.c | 25 ++++++++++----------
 1 file changed, 13 insertions(+), 12 deletions(-)

diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
index 558c7589c329..83ca754250fb 100644
--- a/drivers/irqchip/irq-gic-v3-its.c
+++ b/drivers/irqchip/irq-gic-v3-its.c
@@ -1372,13 +1372,14 @@ static void its_free_device(struct its_device *its_dev)
        kfree(its_dev);
 }
 
-static int its_alloc_device_irq(struct its_device *dev, irq_hw_number_t *hwirq)
+static int its_alloc_device_irq(struct its_device *dev, int nvecs, 
irq_hw_number_t *hwirq)
 {
        int idx;
 
-       idx = find_first_zero_bit(dev->event_map.lpi_map,
-                                 dev->event_map.nr_lpis);
-       if (idx == dev->event_map.nr_lpis)
+       idx = bitmap_find_free_region(dev->event_map.lpi_map,
+                                     dev->event_map.nr_lpis,
+                                     get_count_order(nvecs));
+       if (idx < 0)
                return -ENOSPC;
 
        *hwirq = dev->event_map.lpi_base + idx;
@@ -1464,20 +1465,20 @@ static int its_irq_domain_alloc(struct irq_domain 
*domain, unsigned int virq,
        int err;
        int i;
 
-       for (i = 0; i < nr_irqs; i++) {
-               err = its_alloc_device_irq(its_dev, &hwirq);
-               if (err)
-                       return err;
+       err = its_alloc_device_irq(its_dev, nr_irqs, &hwirq);
+       if (err)
+               return err;
 
-               err = its_irq_gic_domain_alloc(domain, virq + i, hwirq);
+       for (i = 0; i < nr_irqs; i++) {
+               err = its_irq_gic_domain_alloc(domain, virq + i, hwirq + i);
                if (err)
                        return err;
 
                irq_domain_set_hwirq_and_chip(domain, virq + i,
-                                             hwirq, &its_irq_chip, its_dev);
+                                             hwirq + i, &its_irq_chip, 
its_dev);
                pr_debug("ID:%d pID:%d vID:%d\n",
-                        (int)(hwirq - its_dev->event_map.lpi_base),
-                        (int) hwirq, virq + i);
+                        (int)(hwirq + i - its_dev->event_map.lpi_base),
+                        (int)(hwirq + i), virq + i);
        }
 
        return 0;
-- 
2.20.1