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Fri, 18 Jun 2021 12:47:15 -0700 (PDT) Received: from [2620:15c:17:3:3a6:a5d0:1984:a150] ([2620:15c:17:3:3a6:a5d0:1984:a150]) by smtp.gmail.com with ESMTPSA id s1sm9601820pgg.49.2021.06.18.12.47.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 18 Jun 2021 12:47:14 -0700 (PDT) Date: Fri, 18 Jun 2021 12:47:13 -0700 (PDT) From: David Rientjes To: Claudio Imbrenda cc: 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, Uladzislau Rezki , Nicholas Piggin , Andrew Morton , Catalin Marinas , Thomas Gleixner , Ingo Molnar , Christoph Hellwig Subject: Re: [PATCH v4 1/2] mm/vmalloc: add vmalloc_no_huge In-Reply-To: <20210614132357.10202-2-imbrenda@linux.ibm.com> Message-ID: <1ab3bba4-dc91-4f8-ecd5-b18b17ec6d8@google.com> References: <20210614132357.10202-1-imbrenda@linux.ibm.com> <20210614132357.10202-2-imbrenda@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Authentication-Results: imf30.hostedemail.com; dkim=pass header.d=google.com header.s=20161025 header.b=md5MeIpF; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf30.hostedemail.com: domain of rientjes@google.com designates 209.85.216.42 as permitted sender) smtp.mailfrom=rientjes@google.com X-Stat-Signature: wyzcinehe1xzgfpximgygu16d5rdxmsg X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 8DB61E0004DA X-HE-Tag: 1624045636-812120 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, 14 Jun 2021, 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 Acked-by: David Rientjes