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[91.12.102.202]) by smtp.gmail.com with ESMTPSA id 125sm21656180wmb.34.2021.06.14.06.44.49 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 14 Jun 2021 06:44:50 -0700 (PDT) Subject: Re: [PATCH v4 1/2] mm/vmalloc: add vmalloc_no_huge To: Claudio Imbrenda , linux-kernel@vger.kernel.org Cc: kvm@vger.kernel.org, linux-s390@vger.kernel.org, frankja@linux.ibm.com, borntraeger@de.ibm.com, cohuck@redhat.com, linux-mm@kvack.org, Uladzislau Rezki , Nicholas Piggin , Andrew Morton , Catalin Marinas , Thomas Gleixner , Ingo Molnar , David Rientjes , Christoph Hellwig References: <20210614132357.10202-1-imbrenda@linux.ibm.com> <20210614132357.10202-2-imbrenda@linux.ibm.com> From: David Hildenbrand Organization: Red Hat Message-ID: <8f24292e-e8c9-9b9b-0429-2ac984a01611@redhat.com> Date: Mon, 14 Jun 2021 15:44:49 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.10.1 MIME-Version: 1.0 In-Reply-To: <20210614132357.10202-2-imbrenda@linux.ibm.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 14.06.21 15:23, Claudio Imbrenda wrote: > Commit 121e6f3258fe3 ("mm/vmalloc: hugepage vmalloc mappings") added > support for hugepage vmalloc mappings, it also added the flag > VM_NO_HUGE_VMAP for __vmalloc_node_range to request the allocation to > be performed with 0-order non-huge 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 non-huge pages, because of a hardware limitation. > > This patch adds the function vmalloc_no_huge, which works like vmalloc, > but it is guaranteed to always back the mapping using small pages. This > new function is exported, therefore it is usable by modules. > > Signed-off-by: Claudio Imbrenda > Reviewed-by: Uladzislau Rezki (Sony) > Acked-by: Nicholas Piggin > Cc: Andrew Morton > Cc: Nicholas Piggin > Cc: Uladzislau Rezki (Sony) > Cc: Catalin Marinas > Cc: Thomas Gleixner > Cc: Ingo Molnar > Cc: David Rientjes > Cc: Christoph Hellwig > --- > include/linux/vmalloc.h | 1 + > mm/vmalloc.c | 16 ++++++++++++++++ > 2 files changed, 17 insertions(+) > > diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h > index 4d668abb6391..bfaaf0b6fa76 100644 > --- a/include/linux/vmalloc.h > +++ b/include/linux/vmalloc.h > @@ -135,6 +135,7 @@ extern void *__vmalloc_node_range(unsigned long size, unsigned long align, > const void *caller); > void *__vmalloc_node(unsigned long size, unsigned long align, gfp_t gfp_mask, > int node, const void *caller); > +void *vmalloc_no_huge(unsigned long size); > > extern void vfree(const void *addr); > extern void vfree_atomic(const void *addr); > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > index a13ac524f6ff..296a2fcc3fbe 100644 > --- a/mm/vmalloc.c > +++ b/mm/vmalloc.c > @@ -2998,6 +2998,22 @@ void *vmalloc(unsigned long size) > } > EXPORT_SYMBOL(vmalloc); > > +/** > + * vmalloc_no_huge - allocate virtually contiguous memory using small pages > + * @size: allocation size > + * > + * Allocate enough non-huge pages to cover @size from the page level > + * allocator and map them into contiguous kernel virtual space. > + * > + * Return: pointer to the allocated memory or %NULL on error > + */ > +void *vmalloc_no_huge(unsigned long size) > +{ > + return __vmalloc_node_range(size, 1, VMALLOC_START, VMALLOC_END, GFP_KERNEL, PAGE_KERNEL, > + VM_NO_HUGE_VMAP, NUMA_NO_NODE, __builtin_return_address(0)); > +} > +EXPORT_SYMBOL(vmalloc_no_huge); > + > /** > * vzalloc - allocate virtually contiguous memory with zero fill > * @size: allocation size > Reviewed-by: David Hildenbrand -- Thanks, David / dhildenb