[PATCH v8 3/4] xen/arm: account IO handler for emulated PCI host bridge

[Oleksandr Andrushchenko <andr2000@gmail.com>]

From: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>

At the moment, we always allocate an extra 16 slots for IO handlers
(see MAX_IO_HANDLER). So while adding an IO trap handler for the emulated
PCI host bridge we are not breaking anything, but we have a latent bug
as the maximum number of IOs may be exceeded.
Fix this by explicitly telling that we have an additional IO handler, so it is
accounted.

Fixes: d59168dc05a5 ("xen/arm: Enable the existing x86 virtual PCI support for ARM")

Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Acked-by: Julien Grall <jgrall@amazon.com>
---
Since v7:
- updated comment
New in v7
---
 xen/arch/arm/vpci.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/xen/arch/arm/vpci.c b/xen/arch/arm/vpci.c
index 1564448c6c8d..84aaaaebd69d 100644
--- a/xen/arch/arm/vpci.c
+++ b/xen/arch/arm/vpci.c
@@ -124,7 +124,11 @@ unsigned int domain_vpci_get_num_mmio_handlers(struct domain *d)
         return ret < 0 ? 0 : ret;
     }
 
-    return 0;
+    /*
+     * For guests each host bridge requires one region to cover the
+     * configuration space. At the moment, we only expose a single host bridge.
+     */
+    return 1;
 }
 
 /*
-- 
2.25.1