From: Lucas De Marchi <lucas.demarchi@intel.com>
To: Arnd Bergmann <arnd@kernel.org>
Cc: "Oded Gabbay" <ogabbay@kernel.org>,
"Thomas Hellström" <thomas.hellstrom@linux.intel.com>,
"Arnd Bergmann" <arnd@arndb.de>,
"Maarten Lankhorst" <maarten.lankhorst@linux.intel.com>,
"Maxime Ripard" <mripard@kernel.org>,
"Thomas Zimmermann" <tzimmermann@suse.de>,
"David Airlie" <airlied@gmail.com>,
"Daniel Vetter" <daniel@ffwll.ch>,
"Rodrigo Vivi" <rodrigo.vivi@intel.com>,
"Matt Roper" <matthew.d.roper@intel.com>,
"Matthew Brost" <matthew.brost@intel.com>,
intel-xe@lists.freedesktop.org, dri-devel@lists.freedesktop.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 3/3] [v2] drm/xe/xe2: fix 64-bit division in pte_update_size
Date: Mon, 26 Feb 2024 10:40:11 -0600 [thread overview]
Message-ID: <kq3cpbz4ctqvfhtlh7f7wxd7ub3izdjovhv2jqkjasre7u6y2k@exaw42ber3f6> (raw)
In-Reply-To: <20240226124736.1272949-3-arnd@kernel.org>
On Mon, Feb 26, 2024 at 01:46:38PM +0100, Arnd Bergmann wrote:
>From: Arnd Bergmann <arnd@arndb.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: 237412e45390 ("drm/xe: Enable 32bits build")
>Signed-off-by: Arnd Bergmann <arnd@arndb.de>
>---
>v2: use correct Fixes tag
but what about the other comment? How are we supposed to use
DIV_ROUND_UP() but then in some places (which?) have to open code it?
What compiler does this fail on?
>---
> 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;
also the commit message doesn't seem to match the patch as you are only
changing one instance.
Lucas De Marchi
>
> *L0 = size;
> *L0_ofs = xe_migrate_vm_addr(pt_ofs, 0);
>--
>2.39.2
>
next prev parent reply other threads:[~2024-02-26 16:40 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-02-26 12:46 [PATCH 1/3] [v2] drm/xe/kunit: fix link failure with built-in xe Arnd Bergmann
2024-02-26 12:46 ` [PATCH 2/3] [v2] drm/xe/mmio: fix build warning for BAR resize on 32-bit Arnd Bergmann
2024-02-28 15:32 ` Lucas De Marchi
2024-02-26 12:46 ` [PATCH 3/3] [v2] drm/xe/xe2: fix 64-bit division in pte_update_size Arnd Bergmann
2024-02-26 16:40 ` Lucas De Marchi [this message]
2024-02-28 12:26 ` Arnd Bergmann
2024-02-28 15:28 ` Lucas De Marchi
2024-02-28 15:33 ` [PATCH 1/3] [v2] drm/xe/kunit: fix link failure with built-in xe Lucas De Marchi
2024-02-28 19:44 ` Lucas De Marchi
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