linux-kernel - [PATCH 3/3] drm/xe/xe2: fix 64-bit division in pte_update

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Date: Sat, 24 Feb 2024 13:15:01 +0100
From: Arnd Bergmann <arnd@...nel.org>
To: Lucas De Marchi <lucas.demarchi@...el.com>,
	Oded Gabbay <ogabbay@...nel.org>,
	Thomas Hellström <thomas.hellstrom@...ux.intel.com>
Cc: Arnd Bergmann <arnd@...db.de>,
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Maxime Ripard <mripard@...nel.org>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	David Airlie <airlied@...il.com>,
	Daniel Vetter <daniel@...ll.ch>,
	Rodrigo Vivi <rodrigo.vivi@...el.com>,
	Matt Roper <matthew.d.roper@...el.com>,
	Matthew Brost <matthew.brost@...el.com>,
	Himal Prasad Ghimiray <himal.prasad.ghimiray@...el.com>,
	Francois Dugast <francois.dugast@...el.com>,
	Dave Airlie <airlied@...hat.com>,
	intel-xe@...ts.freedesktop.org,
	dri-devel@...ts.freedesktop.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH 3/3] drm/xe/xe2: fix 64-bit division in pte_update_size

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

This function does not build on 32-bit targets when the compiler
fails to reduce DIV_ROUND_UP() into a shift:

ld.lld: error: undefined symbol: __aeabi_uldivmod
>>> referenced by xe_migrate.c
>>>               drivers/gpu/drm/xe/xe_migrate.o:(pte_update_size) in archive vmlinux.a

There are two instances in this function. Change the first to
use an open-coded shift with the same behavior, and the second
one to a 32-bit calculation, which is sufficient here as the size
is never more than 2^32 pages (16TB).

Fixes: ea97a66a2218 ("drm/xe: Disable 32bits build")
Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
 drivers/gpu/drm/xe/xe_migrate.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/xe/xe_migrate.c b/drivers/gpu/drm/xe/xe_migrate.c
index a66fdf2d2991..ee1bb938c493 100644
--- a/drivers/gpu/drm/xe/xe_migrate.c
+++ b/drivers/gpu/drm/xe/xe_migrate.c
@@ -462,7 +462,7 @@ static u32 pte_update_size(struct xe_migrate *m,
 	} else {
 		/* Clip L0 to available size */
 		u64 size = min(*L0, (u64)avail_pts * SZ_2M);
-		u64 num_4k_pages = DIV_ROUND_UP(size, XE_PAGE_SIZE);
+		u32 num_4k_pages = (size + XE_PAGE_SIZE - 1) >> XE_PTE_SHIFT;
 
 		*L0 = size;
 		*L0_ofs = xe_migrate_vm_addr(pt_ofs, 0);
-- 
2.39.2