Re: [PATCH v2 1/2] mm/vmalloc: export __vmalloc_node_range

[Claudio Imbrenda]

On Wed, 9 Jun 2021 16:59:17 +0100
Christoph Hellwig <hch@xxxxxxxxxxxxx> wrote:

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