Re: [Qemu-devel] [PATCH] Fix IDE FDC emulation for no media

[Pavel Hrdina]

On 04/24/2012 09:48 AM, Andreas Färber wrote:
> Am 23.04.2012 18:06, schrieb Pavel Hrdina:
> > Hi,
> > this is the patch to fix incorrect handling of IDE floppy drive controller 
> > emulation
> > when no media is present. If the guest is booted without a media then the drive
> > was not being emulated at all but this patch enables the emulation with no 
> > media present.
> >
> > There was a bug in FDC emulation without media. Driver was not able to 
> > recognize that
> > there is no media in drive.
> >
> > This has been tested on both Fedora-16 x86_64 VM and Windows XP VM and the 
> > behaviour
> > is as expected, i.e. as follows:
> >
> > Linux guest (Fedora 16 x86_64) tries "mount /dev/fd0" and exit with error
> > "mount: /dev/fd0 is not a valid block device" which is the same behavior like
> > bare metal with real floppy device (you have to load floppy driver at first
> > using e.g. "modprobe floppy" command).
> >
> > For Windows XP guest the Windows floppy driver is trying to seek the virtual 
> > drive
> > when you want to open it but driver successfully detect that there is no media 
> > in drive
> > and then it's asking user to insert floppy media in the drive.
> >
> > I also tested behavior of this patch if you start guest with "-nodefaults" and 
> > both
> > Windows and Linux guests detect only FDC but no drive.
> >
> > Pavel
> >
> > This patch has been written with help of specifications from:
> > http://www.ousob.com/ng/hardware/ngd127.php
> > http://www.isdaman.com/alsos/hardware/fdc/floppy.htm
> > http://wiki.osdev.org/Floppy_Disk_Controller
> >
> > Signed-off-by: Pavel Hrdina<address@hidden>
> > Signed-off-by: Michal Novotny<address@hidden>
> > ---
> Please see http://wiki.qemu.org/Contribute/SubmitAPatch for hints on
> writing a commit message for a patch: Subject should have a prefix, such
> as "fdc: Fix emulation for no media" and the body should not contain
> personal letter-style contents such as "Hi, this is the patch". Any such
> personal comments can go under the --- line where they are not committed
> to git history.
>
> Cc'ing floppy author and block maintainer.
>
> Andreas
Thanks for correction, I'll send v2 patch with right commit message.

Pavel
> >   hw/fdc.c |   14 ++++++++++----
> >   hw/pc.c  |    3 ++-
> >   2 files changed, 12 insertions(+), 5 deletions(-)
> >
> > diff --git a/hw/fdc.c b/hw/fdc.c
> > index a0236b7..6791eff 100644
> > --- a/hw/fdc.c
> > +++ b/hw/fdc.c
> > @@ -179,12 +179,14 @@ static void fd_revalidate(FDrive *drv)
> >       FDriveRate rate;
> >
> >       FLOPPY_DPRINTF("revalidate\n");
> > -    if (drv->bs != NULL&&  bdrv_is_inserted(drv->bs)) {
> > +    if (drv->bs != NULL) {
> >           ro = bdrv_is_read_only(drv->bs);
> >           bdrv_get_floppy_geometry_hint(drv->bs,&nb_heads,&max_track,
> >                                         &last_sect, drv->drive,&drive,&rate);
> > -        if (nb_heads != 0&&  max_track != 0&&  last_sect != 0) {
> > -            FLOPPY_DPRINTF("User defined disk (%d %d %d)",
> > +        if (!bdrv_is_inserted(drv->bs)) {
> > +            FLOPPY_DPRINTF("No media in drive\n");
> > +        } else if (nb_heads != 0&&  max_track != 0&&  last_sect != 0) {
> > +            FLOPPY_DPRINTF("User defined disk (%d %d %d)\n",
> >                              nb_heads - 1, max_track, last_sect);
> >           } else {
> >               FLOPPY_DPRINTF("Floppy disk (%d h %d t %d s) %s\n", nb_heads,
> > @@ -201,11 +203,12 @@ static void fd_revalidate(FDrive *drv)
> >           drv->drive = drive;
> >           drv->media_rate = rate;
> >       } else {
> > -        FLOPPY_DPRINTF("No disk in drive\n");
> > +        FLOPPY_DPRINTF("Drive disabled\n");
> >           drv->last_sect = 0;
> >           drv->max_track = 0;
> >           drv->flags&= ~FDISK_DBL_SIDES;
> >       }
> > +
> >   }
> >
> >   /********************************************************/
> > @@ -937,6 +940,9 @@ static int fdctrl_media_changed(FDrive *drv)
> >
> >       if (!drv->bs)
> >           return 0;
> > +    /* This is needed for driver to detect there is no media in drive */
> > +    if (!bdrv_is_inserted(drv->bs))
> > +        return 1;
> >       if (drv->media_changed) {
> >           drv->media_changed = 0;
> >           ret = 1;
> > diff --git a/hw/pc.c b/hw/pc.c
> > index 1f5aacb..29a604b 100644
> > --- a/hw/pc.c
> > +++ b/hw/pc.c
> > @@ -382,7 +382,8 @@ void pc_cmos_init(ram_addr_t ram_size, ram_addr_t 
> > above_4g_mem_size,
> >       if (floppy) {
> >           fdc_get_bs(fd, floppy);
> >           for (i = 0; i<  2; i++) {
> > -            if (fd[i]&&  bdrv_is_inserted(fd[i])) {
> > +            /* If there is no media in a drive, we still have the drive 
> > present */
> > +            if (fd[i]) {
> >                   bdrv_get_floppy_geometry_hint(fd[i],&nb_heads,&max_track,
> >                                                 &last_sect, FDRIVE_DRV_NONE,
> >                                                 &fd_type[i],&rate);