RE: [PATCH v10 03/15] x86/alternatives: Disable LASS when patching kernel alternatives

Luck, Tony
2025-10-22T20:03:09Z

> +/*
> + * LASS enforcement is based on bit 63 of the virtual address. The
> + * kernel is not allowed to touch memory in the lower half of the
> + * virtual address space unless the AC bit is set.
> + *
> + * Use lass_disable()/lass_enable() when accessing kernel (!_PAGE_USER)
> + * mappings in the lower half of the address space that are blocked by
> + * LASS, but not by SMAP.

Maybe "when accessing kernel data ..."

Also add that for instruction fetch CR4.LASS must be cleared.

-Tony