linux-kernel - Re: missing compat-ioctl for CDROM_DRIVE

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Message-Id: <201106171502.39445.arnd@arndb.de>
Date:	Fri, 17 Jun 2011 15:02:39 +0200
From:	Arnd Bergmann <arnd@...db.de>
To:	Johannes Stezenbach <js@...21.net>
Cc:	kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: missing compat-ioctl for CDROM_DRIVE_STATUS + FDGETPRM

On Friday 17 June 2011 11:04:24 Johannes Stezenbach wrote:
> running even a simple "qemu-img create -f qcow2 some.img 1G" causes
> the following in dmesg on a Linux host with linux-2.6.39.1 x86_64 kernel
> and 32bit userspace:
> 
> ioctl32(qemu-img:5296): Unknown cmd fd(3) cmd(00005326){t:'S';sz:0} arg(7fffffff) on some.img
> ioctl32(qemu-img:5296): Unknown cmd fd(3) cmd(801c0204){t:02;sz:28} arg(fff77350) on some.img
> 
> (The same happens when starting a qemu or kvm vm.)
> 
> ioctl 00005326 seems to be CDROM_DRIVE_STATUS,
> ioctl 801c0204 is FDGETPRM.  Both are used in
> qemu/block/raw-posix.c in cdrom_probe_device()
> and floppy_probe_device() respectively.
> 
> FWIW, I'm using qemu/kvm from Debian unstable
> (qemu-0.14.0+dfsg-5.1, qemu-kvm-0.14.1+dfsg-1)

Both are handled by the kernel for block devices, but not for regular
files. The messages may be annoying but they are harmless. We could
silence them either by checking if the file is actually a block device in
qemu-img, or by adding a nop handler to the kernel for regular files.

	Arnd
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