From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:60388) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZAdYA-0005Fp-8l for qemu-devel@nongnu.org; Thu, 02 Jul 2015 08:25:07 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZAdY9-0006Db-1O for qemu-devel@nongnu.org; Thu, 02 Jul 2015 08:25:06 -0400 Message-ID: <55952D97.7040009@redhat.com> Date: Thu, 02 Jul 2015 14:24:55 +0200 From: Laurent Vivier MIME-Version: 1.0 References: In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH] raw-posix.c: remove raw device access for cdrom List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Stefan Hajnoczi , Programmingkid Cc: Kevin Wolf , Peter Maydell , Qemu-block , qemu-devel qemu-devel , Paolo Bonzini , John Snow On 02/07/2015 13:14, Stefan Hajnoczi wrote: > On Wed, Jul 1, 2015 at 11:13 PM, Programmingkid > wrote: >> Fix real cdrom access in Mac OS X so it can be used in QEMU. >> It simply removes the r from a device file's name. This >> allows for a real cdrom to be accessible to the guest. >> It has been successfully tested with a Windows XP guest >> in qemu-system-i386. The qemu-system-ppc emulator doesn't >> quit anymore, but there is another problem that prevents a >> real cdrom from working. >> >> Signed-off-by: John Arbuckle >> >> --- >> block/raw-posix.c | 10 ++++++++++ >> 1 files changed, 10 insertions(+), 0 deletions(-) >> >> diff --git a/block/raw-posix.c b/block/raw-posix.c >> index a967464..3585ed9 100644 >> --- a/block/raw-posix.c >> +++ b/block/raw-posix.c >> @@ -2096,6 +2096,16 @@ static int hdev_open(BlockDriverState *bs, QDict >> *options, int flags, >> kernResult = FindEjectableCDMedia( &mediaIterator ); >> kernResult = GetBSDPath( mediaIterator, bsdPath, sizeof( bsdPath ) >> ); >> >> >> >> + /* >> + * Remove the r from cdrom block device if needed. >> + * /dev/rdisk1 would become /dev/disk1. >> + * The r means raw access. It doesn't work well. >> + */ >> + int sizeOfString = strlen("/dev/r"); >> + if (strncmp("/dev/r", bsdPath, sizeOfString) == 0) { >> + sprintf(bsdPath, "/dev/%s", bsdPath + sizeOfString); >> + } > > Why doesn't raw access "work well"? > > This patch looks like a workaround but you haven't identified the root cause. > > Perhaps because of request alignment requirements? Typically CD-ROMs > have 2 KB block size. You could test this by changing the following > in block_int.h: > #define BLOCK_PROBE_BUF_SIZE 512 > > In that case you need to fix raw-posix.c alignment detection code for > Mac OS X. Look at raw_probe_alignment(). I agree with that, I think we need "s->needs_alignment = true". So in raw_open_common() change "#ifdef __FreeBSD__" by "#ifdef CONFIG_BSD" in: #ifdef __FreeBSD__ if (S_ISCHR(st.st_mode)) { /* * The file is a char device (disk), which on FreeBSD isn't behind * a pager, so force all requests to be aligned. This is needed * so QEMU makes sure all IO operations on the device are aligned * to sector size, or else FreeBSD will reject them with EINVAL. */ s->needs_alignment = true; } #endif Laurent