From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 07DB1C11D05 for ; Thu, 20 Feb 2020 16:13:52 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id CC20D20658 for ; Thu, 20 Feb 2020 16:13:51 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=igalia.com header.i=@igalia.com header.b="XtdssM47" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org CC20D20658 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=igalia.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:45208 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1j4oSV-00047p-0P for qemu-devel@archiver.kernel.org; Thu, 20 Feb 2020 11:13:51 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:55023) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1j4oP2-0006PE-Vi for qemu-devel@nongnu.org; Thu, 20 Feb 2020 11:10:17 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1j4oP1-0006H6-Ul for qemu-devel@nongnu.org; Thu, 20 Feb 2020 11:10:16 -0500 Received: from fanzine.igalia.com ([178.60.130.6]:44733) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1j4oP1-0006Ge-L3; Thu, 20 Feb 2020 11:10:15 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=igalia.com; s=20170329; h=Content-Type:MIME-Version:Message-ID:Date:References:In-Reply-To:Subject:Cc:To:From; bh=BoDL3CgYKgqz4ieNJwO3dh8eKsf9metfbWNPjj37t0o=; b=XtdssM47q2yPOM3sx2U4vFJpAXbqBBgSpR+KL1SGOj0Y4W2pjl+8W4qFi51ki93Gws9C4S5nAIfho3dnV+TmuKwnWQPzgw67vimcrOSmNBgrIHQVBNh610Jgp138i8AZBGJ+ackUV3smz5teP2q6u3EKyPql3wX3cuLNrcTBrsHFWx6vdhG+W8te2Uhb5lsm4dhzeIb1kZmRUznNhp2+SQH2QLrDF6Ht/ONsU8fXbZT1PDpqbjEDxTCKaB1DPLBVtRJNkHb8InUMcLDYYpxa9q8mN8RTiDRZLapZynpyUB2seAIPBB++6FZWOvTNHWIOmMXS+lHpk87iE4eis3ThLg==; Received: from maestria.local.igalia.com ([192.168.10.14] helo=mail.igalia.com) by fanzine.igalia.com with esmtps (Cipher TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim) id 1j4oOz-0005UI-Df; Thu, 20 Feb 2020 17:10:13 +0100 Received: from berto by mail.igalia.com with local (Exim) id 1j4oOz-0006cX-4J; Thu, 20 Feb 2020 17:10:13 +0100 From: Alberto Garcia To: Eric Blake , qemu-devel@nongnu.org Subject: Re: [RFC PATCH v3 05/27] qcow2: Document the Extended L2 Entries feature In-Reply-To: References: <0b884ddcd0ac3a3c0b8cdd9d09c74566ac107c9a.1577014346.git.berto@igalia.com> User-Agent: Notmuch/0.18.2 (http://notmuchmail.org) Emacs/24.4.1 (i586-pc-linux-gnu) Date: Thu, 20 Feb 2020 17:10:13 +0100 Message-ID: MIME-Version: 1.0 Content-Type: text/plain X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x (no timestamps) [generic] [fuzzy] X-Received-From: 178.60.130.6 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: Kevin Wolf , Anton Nefedov , qemu-block@nongnu.org, Max Reitz , Vladimir Sementsov-Ogievskiy , "Denis V . Lunev" Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Thu 20 Feb 2020 03:33:57 PM CET, Eric Blake wrote: >> Given an offset into the virtual disk, the offset into the image file can be >> obtained as follows: >> >> - l2_entries = (cluster_size / sizeof(uint64_t)) >> + l2_entries = (cluster_size / sizeof(uint64_t)) [*] >> >> l2_index = (offset / cluster_size) % l2_entries >> l1_index = (offset / cluster_size) / l2_entries >> @@ -447,6 +455,8 @@ obtained as follows: >> >> return cluster_offset + (offset % cluster_size) >> >> + [*] this changes if Extended L2 Entries are enabled, see next section > >> +The size of an extended L2 entry is 128 bits so the number of entries per table >> +is calculated using this formula: >> + >> + l2_entries = (cluster_size / (2 * sizeof(uint64_t))) > > Is it worth unifying these statements by writing: > > l2_entries = (cluster_size / ((1 + extended_l2) * sizeof(uint64_t))) > > or is that too confusing? I think it's too confusing... Berto