From: Uladzislau Rezki <urezki@gmail.com>
To: Claudio Imbrenda <imbrenda@linux.ibm.com>
Cc: Christoph Hellwig <hch@infradead.org>,
linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
linux-s390@vger.kernel.org, frankja@linux.ibm.com,
borntraeger@de.ibm.com, cohuck@redhat.com, david@redhat.com,
linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>,
Nicholas Piggin <npiggin@gmail.com>,
Uladzislau Rezki <urezki@gmail.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>,
David Rientjes <rientjes@google.com>
Subject: Re: [PATCH v2 1/2] mm/vmalloc: export __vmalloc_node_range
Date: Wed, 9 Jun 2021 18:49:19 +0200 [thread overview]
Message-ID: <20210609164919.GA1938@pc638.lan> (raw)
In-Reply-To: <20210609182809.7ae07aad@ibm-vm>
On Wed, Jun 09, 2021 at 06:28:09PM +0200, Claudio Imbrenda wrote:
> On Wed, 9 Jun 2021 16:59:17 +0100
> Christoph Hellwig <hch@infradead.org> 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?
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
next prev parent reply other threads:[~2021-06-09 16:50 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-08 18:06 [PATCH v2 0/2] mm: export __vmalloc_node_range and use it Claudio Imbrenda
2021-06-08 18:06 ` [PATCH v2 1/2] mm/vmalloc: export __vmalloc_node_range Claudio Imbrenda
2021-06-09 15:59 ` Christoph Hellwig
2021-06-09 16:28 ` Claudio Imbrenda
2021-06-09 16:49 ` Uladzislau Rezki [this message]
2021-06-09 17:50 ` Christian Borntraeger
2021-06-09 17:47 ` Christian Borntraeger
2021-06-10 5:24 ` Christoph Hellwig
2021-06-08 18:06 ` [PATCH v2 2/2] KVM: s390: fix for hugepage vmalloc Claudio Imbrenda
2021-06-08 18:52 ` Christian Borntraeger
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