From: Arnd Bergmann Date: Thu, 1 May 2025 01:25:45 +0000 (-0700) Subject: drm/xe: fix devcoredump chunk alignmnent calculation X-Git-Tag: v6.16-rc1~144^2~13^2~8 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=9c088a5c0d6f019bbc482d433ddddb18db6214f1;p=thirdparty%2Flinux.git drm/xe: fix devcoredump chunk alignmnent calculation The device core dumps are copied in 1.5GB chunks, which leads to a link-time error on 32-bit builds because of the 64-bit division not getting trivially turned into mask and shift operations: ERROR: modpost: "__moddi3" [drivers/gpu/drm/xe/xe.ko] undefined! On top of this, I noticed that the ALIGN_DOWN() usage here cannot work because that is only defined for power-of-two alignments. Change ALIGN_DOWN into an explicit div_u64_rem() that avoids the link error and hopefully produces the right results. Doing a 1.5GB kvmalloc() does seem a bit suspicious as well, e.g. this will clearly fail on any 32-bit platform and is also likely to run out of memory on 64-bit systems under memory pressure, so using a much smaller power-of-two chunk size might be a good idea instead. v2: - Always call div_u64_rem (Matt) Reported-by: kernel test robot Closes: https://lore.kernel.org/oe-kbuild-all/202504251238.JsNgFeFc-lkp@intel.com/ Fixes: c4a2e5f865b7 ("drm/xe: Add devcoredump chunking") Signed-off-by: Arnd Bergmann Signed-off-by: Matthew Brost Reviewed-by: Rodrigo Vivi Link: https://lore.kernel.org/r/20250501012545.1045247-1-matthew.brost@intel.com Signed-off-by: Rodrigo Vivi --- diff --git a/drivers/gpu/drm/xe/xe_devcoredump.c b/drivers/gpu/drm/xe/xe_devcoredump.c index a9e618abf8ac1..7a8af23113180 100644 --- a/drivers/gpu/drm/xe/xe_devcoredump.c +++ b/drivers/gpu/drm/xe/xe_devcoredump.c @@ -177,6 +177,8 @@ static ssize_t xe_devcoredump_read(char *buffer, loff_t offset, struct xe_devcoredump *coredump = data; struct xe_devcoredump_snapshot *ss; ssize_t byte_copied; + u32 chunk_offset; + ssize_t new_chunk_position; if (!coredump) return -ENODEV; @@ -201,10 +203,14 @@ static ssize_t xe_devcoredump_read(char *buffer, loff_t offset, return 0; } + new_chunk_position = div_u64_rem(offset, + XE_DEVCOREDUMP_CHUNK_MAX, + &chunk_offset); + if (offset >= ss->read.chunk_position + XE_DEVCOREDUMP_CHUNK_MAX || offset < ss->read.chunk_position) { - ss->read.chunk_position = - ALIGN_DOWN(offset, XE_DEVCOREDUMP_CHUNK_MAX); + ss->read.chunk_position = new_chunk_position * + XE_DEVCOREDUMP_CHUNK_MAX; __xe_devcoredump_read(ss->read.buffer, XE_DEVCOREDUMP_CHUNK_MAX, @@ -213,8 +219,7 @@ static ssize_t xe_devcoredump_read(char *buffer, loff_t offset, byte_copied = count < ss->read.size - offset ? count : ss->read.size - offset; - memcpy(buffer, ss->read.buffer + - (offset % XE_DEVCOREDUMP_CHUNK_MAX), byte_copied); + memcpy(buffer, ss->read.buffer + chunk_offset, byte_copied); mutex_unlock(&coredump->lock);