[tip: irq/drivers] irqchip/gic-v3-its: Don't clamp nvecs to zero when id_bits is 32

[tip-bot2 for Fuad Tabba]

The following commit has been merged into the irq/drivers branch of tip:

Commit-ID:     5a9d62555e7164ec79a5fe70153d79cf1fdfd614
Gitweb:        https://git.kernel.org/tip/5a9d62555e7164ec79a5fe70153d79cf1fdfd614
Author:        Fuad Tabba <fuad.tabba@xxxxxxxxx>
AuthorDate:    Tue, 08 Sep 2026 15:26:31 +01:00
Committer:     Thomas Gleixner <tglx@xxxxxxxxxx>
CommitterDate: Thu, 15 Oct 2026 11:50:47 +02:00

irqchip/gic-v3-its: Don't clamp nvecs to zero when id_bits is 32

GITS_TYPER_IDBITS is five bits, so id_bits reaches 32 and
min_t(unsigned int, ...) truncates BIT(32) to 0. nvecs becomes 0,
its_lpi_alloc() rejects that, and its_msi_prepare() returns -ENOMEM.
On 32-bit ARM the shift is undefined instead.

The clamp is correct for every value below the maximum, so only that
one value is affected.

Fixes: ce9e40a9a5e5c ("irqchip/gic-v3-its: Limit number of per-device MSIs to the range the ITS supports")
Signed-off-by: Fuad Tabba <fuad.tabba@xxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxx>
Reviewed-by: Marc Zyngier <maz@xxxxxxxxxx>
Reviewed-by: Zenghui Yu (Huawei) <zenghui.yu@xxxxxxxxx>
Reviewed-by: Radu Rendec <radu@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Link: https://patch.msgid.link/20260908142632.2795308-3-fuad.tabba@xxxxxxxxx
---
 drivers/irqchip/irq-gic-v3-its.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
index b6509b4..4f6d4aa 100644
--- a/drivers/irqchip/irq-gic-v3-its.c
+++ b/drivers/irqchip/irq-gic-v3-its.c
@@ -3485,7 +3485,7 @@ static struct its_device *its_create_device(struct its_node *its, u32 dev_id,
 	 * Also honor the ITS's own EID limit.
 	 */
 	id_bits = FIELD_GET(GITS_TYPER_IDBITS, its->typer) + 1;
-	nvecs = min_t(unsigned int, nvecs, BIT(id_bits));
+	nvecs = min_t(u64, nvecs, BIT_ULL(id_bits));
 	nr_ites = max(2, nvecs);
 	sz = nr_ites * (FIELD_GET(GITS_TYPER_ITT_ENTRY_SIZE, its->typer) + 1);
 	sz = max(sz, ITS_ITT_ALIGN);