Re: [Qemu-devel] [PATCH 1/1] vl.c: Since the help says that 'disk_image' is a raw hard disk image, pass format=raw

[Don Slutz <dslutz@verizon.com>]

On 04/30/15 16:15, Kevin Wolf wrote:
> Am 30.04.2015 um 21:15 hat Eric Blake geschrieben:
>> [adding qemu-block]
>> 
>> On 04/30/2015 12:23 PM, Don Slutz wrote:
>>> ~/qemu/out/master/x86_64-softmmu/qemu-system-x86_64 -h | head 
>>> QEMU emulator version 2.3.50, Copyright (c) 2003-2008 Fabrice
>>> Bellard usage: qemu-system-x86_64 [options] [disk_image]
>>> 
>>> 'disk_image' is a raw hard disk image for IDE hard disk 0
>>> 
>>> Standard options: ...
>>> 
>>> Signed-off-by: Don Slutz <dslutz@verizon.com> --- vl.c | 3 ++- 
>>> 1 file changed, 2 insertions(+), 1 deletion(-)
>> 
>> Reviewed-by: Eric Blake <eblake@redhat.com>
>> 
>> Without this, qemu will try to probe formats.  It is  arguably is
>> more convenient when using the shorthand of supplying a disk
>> image to let qemu pick the format; but as the --help text says
>> the image is raw, it's better to be explicit and avoid probing.
>> Besides, we can always use longhand to specify actual format
>> and/or probing if we don't like the shorthand.
> 
> I don't think you can take an outdated help text as a justification
> for breaking backwards compatibility.
> 

Is this a hard no, soft no, or TBD?

The following is what prompted this:

WARNING: Image format was not specified for '/dev/etherd/e500.1' and
probing guessed raw.
         Automatically detecting the format is dangerous for raw
images, write operations on block 0 will be restricted.
         Specify the 'raw' format explicitly to remove the restrictions.


which I would say also breaks backwards compatibility.  However I do
agree that this is the "right" change to have done.  However there
currently is no way to specify that the 'disk_image' is raw.

Also the old options (-hda, -hdb, -hdc, and -hdd) all have similar issues.

So do you want a more complex patch that allows the format to be
specified?

Only for 'disk_image'?

Include -hd* ?

Change the help message also?

   -Don Slutz

> Kevin
> 
>>> 
>>> diff --git a/vl.c b/vl.c index 74c2681..93e674f 100644 ---
>>> a/vl.c +++ b/vl.c @@ -1084,6 +1084,7 @@ static int
>>> cleanup_add_fd(QemuOpts *opts, void *opaque) /* QEMU Block
>>> devices */
>>> 
>>> #define HD_OPTS "media=disk" +#define HD_OPTS_RAW
>>> "media=disk,format=raw" #define CDROM_OPTS "media=cdrom" 
>>> #define FD_OPTS "" #define PFLASH_OPTS "" @@ -2862,7 +2863,7 @@
>>> int main(int argc, char **argv, char **envp) if (optind >=
>>> argc) break; if (argv[optind][0] != '-') { -
>>> hda_opts = drive_add(IF_DEFAULT, 0, argv[optind++], HD_OPTS); +
>>> hda_opts = drive_add(IF_DEFAULT, 0, argv[optind++],
>>> HD_OPTS_RAW); } else { const QEMUOption *popt;
>>> 
>>> 
>> 
>> -- Eric Blake   eblake redhat com    +1-919-301-3266 Libvirt
>> virtualization library http://libvirt.org
>> 
> 
>