linux-kernel - [PATCH] iommu/io-pgtable-arm: dynamically allocate selftest device struct

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Message-Id: <20250411125423.1411061-1-arnd@kernel.org>
Date: Fri, 11 Apr 2025 14:54:11 +0200
From: Arnd Bergmann <arnd@...nel.org>
To: Will Deacon <will@...nel.org>,
	Joerg Roedel <joro@...tes.org>,
	Robin Murphy <robin.murphy@....com>
Cc: Arnd Bergmann <arnd@...db.de>,
	Mostafa Saleh <smostafa@...gle.com>,
	Jason Gunthorpe <jgg@...pe.ca>,
	Kevin Tian <kevin.tian@...el.com>,
	Rob Clark <robdclark@...omium.org>,
	linux-arm-kernel@...ts.infradead.org,
	iommu@...ts.linux.dev,
	linux-kernel@...r.kernel.org
Subject: [PATCH] iommu/io-pgtable-arm: dynamically allocate selftest device struct

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

In general a 'struct device' is way too large to be put on the kernel
stack. Apparently something just caused it to grow a slightly larger,
which pushed the arm_lpae_do_selftests() function over the warning
limit in some configurations:

drivers/iommu/io-pgtable-arm.c:1423:19: error: stack frame size (1032) exceeds limit (1024) in 'arm_lpae_do_selftests' [-Werror,-Wframe-larger-than]
 1423 | static int __init arm_lpae_do_selftests(void)
      |                   ^

Change the function to use a dynamically allocated platform_device
instead of the on-stack device structure. The device is not actually
registered with the system, but is initialized enough to be used here.

Fixes: ca25ec247aad ("iommu/io-pgtable-arm: Remove iommu_dev==NULL special case")
Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 drivers/iommu/io-pgtable-arm.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/drivers/iommu/io-pgtable-arm.c b/drivers/iommu/io-pgtable-arm.c
index 7632c80edea6..9f3bf0b5e8da 100644
--- a/drivers/iommu/io-pgtable-arm.c
+++ b/drivers/iommu/io-pgtable-arm.c
@@ -13,6 +13,7 @@
 #include <linux/bitops.h>
 #include <linux/io-pgtable.h>
 #include <linux/kernel.h>
+#include <linux/platform_device.h>
 #include <linux/sizes.h>
 #include <linux/slab.h>
 #include <linux/types.h>
@@ -1433,15 +1434,17 @@ static int __init arm_lpae_do_selftests(void)
 	};
 
 	int i, j, k, pass = 0, fail = 0;
-	struct device dev;
+	struct platform_device *pdev;
 	struct io_pgtable_cfg cfg = {
 		.tlb = &dummy_tlb_ops,
 		.coherent_walk = true,
-		.iommu_dev = &dev,
 	};
 
-	/* __arm_lpae_alloc_pages() merely needs dev_to_node() to work */
-	set_dev_node(&dev, NUMA_NO_NODE);
+	pdev = platform_device_alloc("io-pgtable-test", 0);
+	if (!pdev)
+		return -ENOMEM;
+
+	cfg.iommu_dev = &pdev->dev;
 
 	for (i = 0; i < ARRAY_SIZE(pgsize); ++i) {
 		for (j = 0; j < ARRAY_SIZE(address_size); ++j) {
@@ -1461,6 +1464,8 @@ static int __init arm_lpae_do_selftests(void)
 	}
 
 	pr_info("selftest: completed with %d PASS %d FAIL\n", pass, fail);
+	platform_device_put(pdev);
+
 	return fail ? -EFAULT : 0;
 }
 subsys_initcall(arm_lpae_do_selftests);
-- 
2.39.5