On Wed, Jun 09, 2021 at 06:28:09PM +0200, Claudio Imbrenda wrote:

On Wed, 9 Jun 2021 16:59:17 +0100
Christoph Hellwig [off-list ref] wrote:

quoted

On Tue, Jun 08, 2021 at 08:06:17PM +0200, Claudio Imbrenda wrote:

quoted

The recent patches to add support for hugepage vmalloc mappings
added a flag for __vmalloc_node_range to allow to request small
pages. This flag is not accessible when calling vmalloc, the only
option is to call directly __vmalloc_node_range, which is not
exported.

This means that a module can't vmalloc memory with small pages.

Case in point: KVM on s390x needs to vmalloc a large area, and it
needs to be mapped with small pages, because of a hardware
limitation.

This patch exports __vmalloc_node_range so it can be used in modules
too.  

No.  I spent a lot of effort to mak sure such a low-level API is
not exported.

ok, but then how can we vmalloc memory with small pages from KVM?

Does the s390x support CONFIG_HAVE_ARCH_HUGE_VMALLOC what is arch
specific?

If not then small pages are used. Or am i missing something?

I agree with Christoph that exporting a low level internals
is not a good idea.

--
Vlad Rezki