[PATCH 2/3] irqchip/gic-v3-its: Zero ITTs reused from the ITT pool

[Fuad Tabba <fuad.tabba@linux.dev>]

Commit b08e2f42e86b5 ("irqchip/gic-v3-its: Share ITS tables with a
non-trusted hypervisor") moved sub-page ITTs from kzalloc_node() to a
genpool. The pages added to the pool are zeroed, but an ITT freed back
to it goes to the next device as the previous one left it. MAPD is then
UNPREDICTABLE: "When V == 1, the specified ITT does not contain all
zeros" (IHI 0069H.b, 5.3.10).

Zero the ITT when it comes from the pool.

Fixes: b08e2f42e86b5 ("irqchip/gic-v3-its: Share ITS tables with a non-trusted hypervisor")
Signed-off-by: Fuad Tabba <fuad.tabba@linux.dev>
---
 drivers/irqchip/irq-gic-v3-its.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
index 5613c52adf88e..5c3ab9d30f6af 100644
--- a/drivers/irqchip/irq-gic-v3-its.c
+++ b/drivers/irqchip/irq-gic-v3-its.c
@@ -267,8 +267,10 @@ static void *itt_alloc_pool(int node, int size)
 
 	do {
 		addr = gen_pool_alloc(itt_pool, size);
-		if (addr)
+		if (addr) {
+			memset((void *)addr, 0, size);
 			break;
+		}
 
 		page = its_alloc_pages_node(node, GFP_KERNEL | __GFP_ZERO, 0);
 		if (!page)
-- 
2.47.3