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[174.95.95.253]) by smtp.gmail.com with ESMTPSA id c125sm2082676qke.117.2021.03.05.07.51.41 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 05 Mar 2021 07:51:42 -0800 (PST) Date: Fri, 5 Mar 2021 10:51:41 -0500 From: Peter Xu To: David Hildenbrand Subject: Re: [PATCH v2 8/9] util/mmap-alloc: Support RAM_NORESERVE via MAP_NORESERVE Message-ID: <20210305155141.GI397383@xz-x1> References: <20210305101634.10745-1-david@redhat.com> <20210305101634.10745-9-david@redhat.com> <20210305154206.GH397383@xz-x1> MIME-Version: 1.0 In-Reply-To: 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 , "Michael S. Tsirkin" , 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 04:44:36PM +0100, David Hildenbrand wrote: > On 05.03.21 16:42, Peter Xu wrote: > > On Fri, Mar 05, 2021 at 11:16:33AM +0100, David Hildenbrand wrote: > > > +#define OVERCOMMIT_MEMORY_PATH "/proc/sys/vm/overcommit_memory" > > > +static bool map_noreserve_effective(int fd, bool readonly, bool shared) > > > +{ > > > > [...] > > > > > @@ -184,8 +251,7 @@ void *qemu_ram_mmap(int fd, > > > size_t offset, total; > > > void *ptr, *guardptr; > > > - if (noreserve) { > > > - error_report("Skipping reservation of swap space is not supported"); > > > + if (noreserve && !map_noreserve_effective(fd, shared, readonly)) { > > > > Need to switch "shared" & "readonly"? > > Indeed, interestingly it has the same effect (as we don't have anonymous > read-only memory in QEMU :) ) But note there is still a "g_assert(!shared || fd >= 0);" inside.. :) > > (wouldn't have happened with flags ... hmm) Right. -- Peter Xu