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[174.95.95.253]) by smtp.gmail.com with ESMTPSA id a9sm1995727qtx.96.2021.03.05.07.37.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 05 Mar 2021 07:37:15 -0800 (PST) Date: Fri, 5 Mar 2021 10:37:13 -0500 From: Peter Xu To: David Hildenbrand Subject: Re: [PATCH v2 7/9] memory: introduce RAM_NORESERVE and wire it up in qemu_ram_mmap() Message-ID: <20210305153713.GG397383@xz-x1> References: <20210305101634.10745-1-david@redhat.com> <20210305101634.10745-8-david@redhat.com> MIME-Version: 1.0 In-Reply-To: <20210305101634.10745-8-david@redhat.com> Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=peterx@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Received-SPF: pass client-ip=216.205.24.124; envelope-from=peterx@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Thomas Huth , Cornelia Huck , Eduardo Habkost , kvm@vger.kernel.org, "Michael S. Tsirkin" , qemu-s390x@nongnu.org, Stefan Weil , Murilo Opsfelder Araujo , Richard Henderson , "Dr. David Alan Gilbert" , Juan Quintela , qemu-devel@nongnu.org, Halil Pasic , Christian Borntraeger , Greg Kurz , Stefan Hajnoczi , Igor Mammedov , Paolo Bonzini , Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= , Igor Kotrasinski Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Fri, Mar 05, 2021 at 11:16:32AM +0100, David Hildenbrand wrote: > Let's introduce RAM_NORESERVE, allowing mmap'ing with MAP_NORESERVE. The > new flag has the following semantics: > > RAM is mmap-ed with MAP_NORESERVE. When set, reserving swap space (or > huge pages on Linux) is skipped: will bail out if not supported. When not > set, the OS might reserve swap space (or huge pages on Linux), depending > on OS support. > > Allow passing it into: > - memory_region_init_ram_nomigrate() > - memory_region_init_resizeable_ram() > - memory_region_init_ram_from_file() > > ... and teach qemu_ram_mmap() and qemu_anon_ram_alloc() about the flag. > Bail out if the flag is not supported, which is the case right now for > both, POSIX and win32. We will add the POSIX mmap implementation next and > allow specifying RAM_NORESERVE via memory backends. > > The target use case is virtio-mem, which dynamically exposes memory > inside a large, sparse memory area to the VM. > > Cc: Juan Quintela > Cc: Halil Pasic > Cc: Cornelia Huck > Cc: Christian Borntraeger > Cc: Thomas Huth > Cc: Stefan Weil > Cc: kvm@vger.kernel.org > Cc: qemu-s390x@nongnu.org > Signed-off-by: David Hildenbrand Reviewed-by: Peter Xu -- Peter Xu