On 6/28/24 5:47 PM, Kees Cook wrote:

On Thu, Jun 27, 2024 at 10:35:36PM -0700, Boqun Feng wrote:

quoted

On Thu, Jun 20, 2024 at 10:43:39PM +0200, Vlastimil Babka wrote:

quoted

Rust people were asking about kmalloc alignment (but I forgot the details)

It was me! The ask is whether we can specify the alignment for the
allocation API, for example, requesting a size=96 and align=32 memory,
or the allocation API could do a "best alignment", for example,
allocating a size=96 will give a align=32 memory. As far as I
understand, kmalloc() doesn't support this.

I can drop the "align" argument. Do we want to hard-code a
per-cache-size alignment for the caches in a kmem_buckets collection?

I think you can drop it as a single value is really ill suited for a
collection of different sizes.

As for Rust's requirements we could consider whether to add a special flag
if they use own bucket, or just implement the rules for non-power-of-two
size globally. It should be feasible as I think in the non-debug caches it
shouldn't in fact change the existing layout, which is the same situation as
when we codified the power-of-two caches alignment as guaranteed.