From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([209.51.188.92]:51246) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gpGZL-0005ku-7Z for qemu-devel@nongnu.org; Thu, 31 Jan 2019 12:56:08 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1gpGZK-00055X-2E for qemu-devel@nongnu.org; Thu, 31 Jan 2019 12:56:07 -0500 From: Kevin Wolf Date: Thu, 31 Jan 2019 18:55:39 +0100 Message-Id: <20190131175549.11691-2-kwolf@redhat.com> In-Reply-To: <20190131175549.11691-1-kwolf@redhat.com> References: <20190131175549.11691-1-kwolf@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Subject: [Qemu-devel] [RFC PATCH 01/11] qcow2: Extend spec for external data files List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-block@nongnu.org Cc: kwolf@redhat.com, mreitz@redhat.com, eblake@redhat.com, qemu-devel@nongnu.org This adds external data file to the qcow2 spec as a new incompatible feature. Signed-off-by: Kevin Wolf --- docs/interop/qcow2.txt | 19 ++++++++++++++++--- 1 file changed, 16 insertions(+), 3 deletions(-) diff --git a/docs/interop/qcow2.txt b/docs/interop/qcow2.txt index fb5cb47245..90af0d02e5 100644 --- a/docs/interop/qcow2.txt +++ b/docs/interop/qcow2.txt @@ -97,7 +97,17 @@ in the description of a field. be written to (unless for regaining consistency). =20 - Bits 2-63: Reserved (set to 0) + Bit 2: External data file. If this bit is set, = an + external data file name header extension= must + be present as well. Guest clusters are t= hen + stored in the external data file. For su= ch + images, clusters in the external data fi= le are + not refcounted. The offset field in the + Standard Cluster Descriptor must match t= he + guest offset and neither compressed clus= ters + nor internal snapshots are supported. + + Bits 3-63: Reserved (set to 0) =20 80 - 87: compatible_features Bitmask of compatible features. An implementation ca= n @@ -148,6 +158,7 @@ be stored. Each extension has a structure like the fo= llowing: 0x6803f857 - Feature name table 0x23852875 - Bitmaps extension 0x0537be77 - Full disk encryption header pointer + 0x44415441 - External data file name other - Unknown header extension, can be sa= fely ignored =20 @@ -450,8 +461,10 @@ Standard Cluster Descriptor: 1 - 8: Reserved (set to 0) =20 9 - 55: Bits 9-55 of host cluster offset. Must be aligned to= a - cluster boundary. If the offset is 0, the cluster is - unallocated. + cluster boundary. If the offset is 0 and bit 63 is c= lear, + the cluster is unallocated. The offset may only be 0= with + bit 63 set (indicating a host cluster offset of 0) w= hen an + external data file is used. =20 56 - 61: Reserved (set to 0) =20 --=20 2.20.1