linux-kernel - [PATCH] irqchip: gic-v3-its: avoid truncating memory addresses

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Message-Id: <20260119201603.2713066-1-arnd@kernel.org>
Date: Mon, 19 Jan 2026 21:15:12 +0100
From: Arnd Bergmann <arnd@...nel.org>
To: Marc Zyngier <maz@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>
Cc: Arnd Bergmann <arnd@...db.de>,
	Lorenzo Pieralisi <lpieralisi@...nel.org>,
	linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] irqchip: gic-v3-its: avoid truncating memory addresses

From: Arnd Bergmann <arnd@...db.de>

On 32-bit machines with CONFIG_ARM_LPAE, it is possible for lowmem
allocations to be backed by addresses physical memory above the 32-bit
address limit, as I found while experimenting with larger VMSPLIT
configurations.

This caused the qemu virt model to crash in the GICv3 driver, which
allocates the 'itt' object using GFP_KERNEL. Since all memory below
the 4GB physical address limit is in ZONE_DMA in this configuration,
kmalloc defaults to higher addresses for ZONE_NORMAL, and the
its driver stores the physical address in a 32-bit 'unsigned long'
variable.

Change the itt_addr variable to the correct phys_addr_t type instead,
along with all other variables in this driver that hold a physical
address.

I checked the gicv5 driver for the same problem, and it correctly
uses u64 variables, while all other irqchip drivers don't call
virt_to_phys or similar interfaces. I expect other drivers to
have similar issues, but fixing this one is sufficient for
booting a virtio based guest.

Fixes: cc2d3216f53c ("irqchip: GICv3: ITS command queue")
Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 drivers/irqchip/irq-gic-v3-its.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
index ada585bfa451..2988def30972 100644
--- a/drivers/irqchip/irq-gic-v3-its.c
+++ b/drivers/irqchip/irq-gic-v3-its.c
@@ -709,7 +709,7 @@ static struct its_collection *its_build_mapd_cmd(struct its_node *its,
 						 struct its_cmd_block *cmd,
 						 struct its_cmd_desc *desc)
 {
-	unsigned long itt_addr;
+	phys_addr_t itt_addr;
 	u8 size = ilog2(desc->its_mapd_cmd.dev->nr_ites);

 	itt_addr = virt_to_phys(desc->its_mapd_cmd.dev->itt);
@@ -879,7 +879,7 @@ static struct its_vpe *its_build_vmapp_cmd(struct its_node *its,
 					   struct its_cmd_desc *desc)
 {
 	struct its_vpe *vpe = valid_vpe(its, desc->its_vmapp_cmd.vpe);
-	unsigned long vpt_addr, vconf_addr;
+	phys_addr_t vpt_addr, vconf_addr;
 	u64 target;
 	bool alloc;

@@ -2477,10 +2477,10 @@ static int its_setup_baser(struct its_node *its, struct its_baser *baser,
 	baser->psz = psz;
 	tmp = indirect ? GITS_LVL1_ENTRY_SIZE : esz;

-	pr_info("ITS@%pa: allocated %d %s @%lx (%s, esz %d, psz %dK, shr %d)\n",
+	pr_info("ITS@%pa: allocated %d %s @%llx (%s, esz %d, psz %dK, shr %d)\n",
 		&its->phys_base, (int)(PAGE_ORDER_TO_SIZE(order) / (int)tmp),
 		its_base_type_string[type],
-		(unsigned long)virt_to_phys(base),
+		(u64)virt_to_phys(base),
 		indirect ? "indirect" : "flat", (int)esz,
 		psz / SZ_1K, (int)shr >> GITS_BASER_SHAREABILITY_SHIFT);

-- 
2.39.5