On Wed, 2 Apr 2025 09:42:00 -0700 Linus Torvalds <[email protected]> wrote:
> Wait, what? > > Didn't you just say that you can just use page_address() for the kernel > mapping? Correct. I misunderstood Mike when he created the reserve_mem and had it return physical addresses. I didn't realize he had it already mapped via the normal virtual mappings. > > So the whole vmap thing is entirely unnecessary in the first place. > > Including the simpler vmap_page_range(). Not entirely. The original code only used memmap=, which does require the vmap_page_range(). The reserve_mem came later, and thinking it was just physical address space (not a mapping), I just had it use the memmap code. That is, the persistent memory buffer was originally created on top of the memmap feature (and only for x86). I talked with Mike about making it more generic and he and I worked out the reserve_mem option. Having the memmap code already doing the vmap() I just had the reserve_mem version use the same, not knowing that it could just use phys_to_virt(). This patch series fixes that miscommunication and separates out a memmap'ed buffer from reserve_mem buffer and simplifies everything. -- Steve
