From: Arnd Bergmann <a...@arndb.de> 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. Fixes: c4a2e5f865b7 ("drm/xe: Add devcoredump chunking") Signed-off-by: Arnd Bergmann <a...@arndb.de> --- Please test this with multi-gigabyte buffers, the original code was clearly not right, but I don't trust my version either. --- drivers/gpu/drm/xe/xe_devcoredump.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/drivers/gpu/drm/xe/xe_devcoredump.c b/drivers/gpu/drm/xe/xe_devcoredump.c index a9e618abf8ac..4eb70e2d9f68 100644 --- a/drivers/gpu/drm/xe/xe_devcoredump.c +++ b/drivers/gpu/drm/xe/xe_devcoredump.c @@ -177,6 +177,7 @@ 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; if (!coredump) return -ENODEV; @@ -203,8 +204,9 @@ static ssize_t xe_devcoredump_read(char *buffer, loff_t 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 = div_u64_rem(offset, + XE_DEVCOREDUMP_CHUNK_MAX, &chunk_offset) + * XE_DEVCOREDUMP_CHUNK_MAX; __xe_devcoredump_read(ss->read.buffer, XE_DEVCOREDUMP_CHUNK_MAX, @@ -213,8 +215,7 @@ 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); -- 2.39.5