[Intel-gfx] [v3] drm/i915/ttm: fix sg_table construction

[Guenter Roeck]

On Mon, Jul 11, 2022 at 09:58:59AM +0100, Matthew Auld wrote:
> If we encounter some monster sized local-memory page that exceeds the
> maximum sg length (UINT32_MAX), ensure that don't end up with some
> misaligned address in the entry that follows, leading to fireworks
> later. Also ensure we have some coverage of this in the selftests.
> 
> v2(Chris):
>   - Use round_down consistently to avoid udiv errors
> v3(Nirmoy):
>   - Also update the max_segment in the selftest
> 
> Fixes: f701b16d4cc5 ("drm/i915/ttm: add i915_sg_from_buddy_resource")
> Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/6379
> Signed-off-by: Matthew Auld <matthew.auld at intel.com>
> Cc: Thomas Hellström <thomas.hellstrom at linux.intel.com>
> Cc: Nirmoy Das <nirmoy.das at linux.intel.com>
> Reviewed-by: Nirmoy Das <nirmoy.das at intel.com>

Building i386:defconfig ... failed
--------------
Error log:
x86_64-linux-ld: drivers/gpu/drm/i915/i915_scatterlist.o: in function `i915_rsgt_from_mm_node':
i915_scatterlist.c:(.text+0x196): undefined reference to `__udivdi3'

Bisect log attached.

Guenter

---
# bad: [9b59ec8d50a1f28747ceff9a4f39af5deba9540e] Merge tag 'riscv-for-linus-5.19-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/riscv/linux
# good: [e5d523f1ae8f2cef01f8e071aeee432654166708] ubsan: disable UBSAN_DIV_ZERO for clang
git bisect start 'HEAD' 'e5d523f1ae8f'
# bad: [2a347a06ebb1b186a5cb919c9f5ab6e040554be7] Merge tag 'platform-drivers-x86-v5.19-4' of git://git.kernel.org/pub/scm/linux/kernel/git/pdx86/platform-drivers-x86
git bisect bad 2a347a06ebb1b186a5cb919c9f5ab6e040554be7
# bad: [093f8d8f10aa22935bc8bf7100700f714ebaba9c] Merge tag 'amd-drm-fixes-5.19-2022-07-13' of https://gitlab.freedesktop.org/agd5f/linux into drm-fixes
git bisect bad 093f8d8f10aa22935bc8bf7100700f714ebaba9c
# bad: [ad765fae792e16ce3c1d0b69ce939e3f7dba40ab] drm/i915/gem: Look for waitboosting across the whole object prior to individual waits
git bisect bad ad765fae792e16ce3c1d0b69ce939e3f7dba40ab
# good: [f99546298a4537965b75d518c210742f641be389] Merge tag 'gvt-fixes-2022-07-11' of https://github.com/intel/gvt-linux into drm-intel-fixes
git bisect good f99546298a4537965b75d518c210742f641be389
# bad: [aff1e0b09b54b64944b7fe32997229552737b9e9] drm/i915/ttm: fix sg_table construction
git bisect bad aff1e0b09b54b64944b7fe32997229552737b9e9
# good: [896dcabd1f8f613c533d948df17408c41f8929f5] drm/i915/selftests: fix a couple IS_ERR() vs NULL tests
git bisect good 896dcabd1f8f613c533d948df17408c41f8929f5
# first bad commit: [aff1e0b09b54b64944b7fe32997229552737b9e9] drm/i915/ttm: fix sg_table construction