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Mon, 08 Mar 2021 10:07:27 -0500 Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-234-NZrrJDi-MUemDr_Qg4UD5A-1; Mon, 08 Mar 2021 10:07:24 -0500 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 797D61966321; Mon, 8 Mar 2021 15:07:22 +0000 (UTC) Received: from t480s.redhat.com (ovpn-113-123.ams2.redhat.com [10.36.113.123]) by smtp.corp.redhat.com (Postfix) with ESMTP id ED8165D9CD; Mon, 8 Mar 2021 15:07:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1615216045; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=IcSEGod7KTi/JjEkRbArfe4hY+fUndoBU72cDZ+8n6E=; b=aRxYtRux0gez0+beaWbBU6piGFz0WIXLiHHNJuu102/10wRMv/Xg+kiwCe2d4g5uSR/xTx CdtBl3cR+1LrFfGHxJS1feT6n6JIJt8hdnxo6WfTvaY0LpiEqsT7It4FPJpIV3QsVJkGzs 6FOpiqj+JS7ugpXx2CPKm8qMHYfZ0Jo= X-MC-Unique: NZrrJDi-MUemDr_Qg4UD5A-1 From: David Hildenbrand To: qemu-devel@nongnu.org Subject: [PATCH v3 05/12] util/mmap-alloc: Factor out reserving of a memory region to mmap_reserve() Date: Mon, 8 Mar 2021 16:05:53 +0100 Message-Id: <20210308150600.14440-6-david@redhat.com> In-Reply-To: <20210308150600.14440-1-david@redhat.com> References: <20210308150600.14440-1-david@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=david@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: quoted-printable Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=63.128.21.124; envelope-from=david@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -29 X-Spam_score: -3.0 X-Spam_bar: --- X-Spam_report: (-3.0 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.251, 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_H4=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: Marcel Apfelbaum , Murilo Opsfelder Araujo , Cornelia Huck , Eduardo Habkost , "Michael S. Tsirkin" , Stefan Weil , David Hildenbrand , Richard Henderson , "Dr. David Alan Gilbert" , Peter Xu , Greg Kurz , Halil Pasic , Christian Borntraeger , Stefan Hajnoczi , Igor Mammedov , Thomas Huth , Paolo Bonzini , =?UTF-8?q?Philippe=20Mathieu-Daud=C3=A9?= , Igor Kotrasinski , Juan Quintela Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail-DKIM: fail (Header signature does not verify) Content-Type: text/plain; charset="utf-8" We want to reserve a memory region without actually populating memory. Let's factor that out. Reviewed-by: Igor Kotrasinski Acked-by: Murilo Opsfelder Araujo Reviewed-by: Richard Henderson Reviewed-by: Peter Xu Signed-off-by: David Hildenbrand --- util/mmap-alloc.c | 58 +++++++++++++++++++++++++++-------------------- 1 file changed, 33 insertions(+), 25 deletions(-) diff --git a/util/mmap-alloc.c b/util/mmap-alloc.c index 24854064b4..223d66219c 100644 --- a/util/mmap-alloc.c +++ b/util/mmap-alloc.c @@ -82,6 +82,38 @@ size_t qemu_mempath_getpagesize(const char *mem_path) return qemu_real_host_page_size; } =20 +/* + * Reserve a new memory region of the requested size to be used for mapping + * from the given fd (if any). + */ +static void *mmap_reserve(size_t size, int fd) +{ + int flags =3D MAP_PRIVATE; + +#if defined(__powerpc64__) && defined(__linux__) + /* + * On ppc64 mappings in the same segment (aka slice) must share the sa= me + * page size. Since we will be re-allocating part of this segment + * from the supplied fd, we should make sure to use the same page size= , to + * this end we mmap the supplied fd. In this case, set MAP_NORESERVE = to + * avoid allocating backing store memory. + * We do this unless we are using the system page size, in which case + * anonymous memory is OK. + */ + if (fd =3D=3D -1 || qemu_fd_getpagesize(fd) =3D=3D qemu_real_host_page= _size) { + fd =3D -1; + flags |=3D MAP_ANONYMOUS; + } else { + flags |=3D MAP_NORESERVE; + } +#else + fd =3D -1; + flags |=3D MAP_ANONYMOUS; +#endif + + return mmap(0, size, PROT_NONE, flags, fd, 0); +} + static inline size_t mmap_guard_pagesize(int fd) { #if defined(__powerpc64__) && defined(__linux__) @@ -104,7 +136,6 @@ void *qemu_ram_mmap(int fd, int prot; int flags; int map_sync_flags =3D 0; - int guardfd; size_t offset; size_t total; void *guardptr; @@ -116,30 +147,7 @@ void *qemu_ram_mmap(int fd, */ total =3D size + align; =20 -#if defined(__powerpc64__) && defined(__linux__) - /* On ppc64 mappings in the same segment (aka slice) must share the sa= me - * page size. Since we will be re-allocating part of this segment - * from the supplied fd, we should make sure to use the same page size= , to - * this end we mmap the supplied fd. In this case, set MAP_NORESERVE = to - * avoid allocating backing store memory. - * We do this unless we are using the system page size, in which case - * anonymous memory is OK. - */ - flags =3D MAP_PRIVATE; - if (fd =3D=3D -1 || guard_pagesize =3D=3D qemu_real_host_page_size) { - guardfd =3D -1; - flags |=3D MAP_ANONYMOUS; - } else { - guardfd =3D fd; - flags |=3D MAP_NORESERVE; - } -#else - guardfd =3D -1; - flags =3D MAP_PRIVATE | MAP_ANONYMOUS; -#endif - - guardptr =3D mmap(0, total, PROT_NONE, flags, guardfd, 0); - + guardptr =3D mmap_reserve(total, fd); if (guardptr =3D=3D MAP_FAILED) { return MAP_FAILED; } --=20 2.29.2