[Qemu-devel] [PATCH v2] docs/specs/qcow2.txt: fix incorrect bits of offsets in entries

[Qemu-devel] [PATCH v2] docs/specs/qcow2.txt: fix incorrect bits of offsets in entries

[Hu Tao]

Fix incorrect bits of offsets in refcount table entry, l1 table
entry and l2 table entry. See REFT_OFFSET_MASK, L1E_OFFSET_MASK
and L2E_OFFSET_MASK.

Fix a typo while at the file.

Signed-off-by: Hu Tao <hutao@cn.fujitsu.com>
---

v2: update comments as well.

 docs/specs/qcow2.txt | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/docs/specs/qcow2.txt b/docs/specs/qcow2.txt
index f19536a..0abf196 100644
--- a/docs/specs/qcow2.txt
+++ b/docs/specs/qcow2.txt
@@ -192,9 +192,9 @@ as follows:
 
 Refcount table entry:
 
-    Bit  0 -  8:    Reserved (set to 0)
+    Bit  0 -  7:    Reserved (set to 0)
 
-         9 - 63:    Bits 9-63 of the offset into the image file at which the
+         8 - 63:    Bits 8-63 of the offset into the image file at which the
                     refcount block starts. Must be aligned to a cluster
                     boundary.
 
@@ -218,7 +218,7 @@ The L1 table has a variable size (stored in the header) and may use multiple
 clusters, however it must be contiguous in the image file. L2 tables are
 exactly one cluster in size.
 
-Given a offset into the virtual disk, the offset into the image file can be
+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))
@@ -233,9 +233,9 @@ obtained as follows:
 
 L1 table entry:
 
-    Bit  0 -  8:    Reserved (set to 0)
+    Bit  0 -  7:    Reserved (set to 0)
 
-         9 - 55:    Bits 9-55 of the offset into the image file at which the L2
+         8 - 55:    Bits 8-55 of the offset into the image file at which the L2
                     table starts. Must be aligned to a cluster boundary. If the
                     offset is 0, the L2 table and all clusters described by this
                     L2 table are unallocated.
@@ -268,9 +268,9 @@ Standard Cluster Descriptor:
 
                     With version 2, this is always 0.
 
-         1 -  8:    Reserved (set to 0)
+         1 -  7:    Reserved (set to 0)
 
-         9 - 55:    Bits 9-55 of host cluster offset. Must be aligned to a
+         8 - 55:    Bits 8-55 of host cluster offset. Must be aligned to a
                     cluster boundary. If the offset is 0, the cluster is
                     unallocated.
 
-- 
1.7.11.7

Re: [Qemu-devel] [PATCH v2] docs/specs/qcow2.txt: fix incorrect bits of offsets in entries

[Stefan Hajnoczi]

On Mon, Dec 30, 2013 at 04:00:17PM +0800, Hu Tao wrote:
> Fix incorrect bits of offsets in refcount table entry, l1 table
> entry and l2 table entry. See REFT_OFFSET_MASK, L1E_OFFSET_MASK
> and L2E_OFFSET_MASK.
> 
> Fix a typo while at the file.
> 
> Signed-off-by: Hu Tao <hutao@cn.fujitsu.com>
> ---
> 
> v2: update comments as well.
> 
>  docs/specs/qcow2.txt | 14 +++++++-------
>  1 file changed, 7 insertions(+), 7 deletions(-)

Thanks, applied to my block tree:
https://github.com/stefanha/qemu/commits/block

Stefan

Re: [Qemu-devel] [PATCH v2] docs/specs/qcow2.txt: fix incorrect bits of offsets in entries

[Kevin Wolf]

Am 17.01.2014 um 08:40 hat Stefan Hajnoczi geschrieben:
> On Mon, Dec 30, 2013 at 04:00:17PM +0800, Hu Tao wrote:
> > Fix incorrect bits of offsets in refcount table entry, l1 table
> > entry and l2 table entry. See REFT_OFFSET_MASK, L1E_OFFSET_MASK
> > and L2E_OFFSET_MASK.
> > 
> > Fix a typo while at the file.
> > 
> > Signed-off-by: Hu Tao <hutao@cn.fujitsu.com>
> > ---
> > 
> > v2: update comments as well.
> > 
> >  docs/specs/qcow2.txt | 14 +++++++-------
> >  1 file changed, 7 insertions(+), 7 deletions(-)
> 
> Thanks, applied to my block tree:
> https://github.com/stefanha/qemu/commits/block

This patch is wrong. It's the qcow2.h #defines that need to be fixed,
not the spec. The smallest possible cluster size is 512 bytes, i.e.
nine zero bits at the end, not just eight.

Kevin

Re: [Qemu-devel] [PATCH v2] docs/specs/qcow2.txt: fix incorrect bits of offsets in entries

[Hu Tao]

On Mon, Jan 20, 2014 at 10:10:22AM +0100, Kevin Wolf wrote:
> Am 17.01.2014 um 08:40 hat Stefan Hajnoczi geschrieben:
> > On Mon, Dec 30, 2013 at 04:00:17PM +0800, Hu Tao wrote:
> > > Fix incorrect bits of offsets in refcount table entry, l1 table
> > > entry and l2 table entry. See REFT_OFFSET_MASK, L1E_OFFSET_MASK
> > > and L2E_OFFSET_MASK.
> > > 
> > > Fix a typo while at the file.
> > > 
> > > Signed-off-by: Hu Tao <hutao@cn.fujitsu.com>
> > > ---
> > > 
> > > v2: update comments as well.
> > > 
> > >  docs/specs/qcow2.txt | 14 +++++++-------
> > >  1 file changed, 7 insertions(+), 7 deletions(-)
> > 
> > Thanks, applied to my block tree:
> > https://github.com/stefanha/qemu/commits/block
> 
> This patch is wrong. It's the qcow2.h #defines that need to be fixed,
> not the spec. The smallest possible cluster size is 512 bytes, i.e.
> nine zero bits at the end, not just eight.

You're right. Thanks to bit 8 in these entries are reserved as zero,
we're not running into problem with wrong masks.