Recent floppy boot regression in qemu-system-i386

[Andreas Gustafsson]

In recent versions of qemu-system-i386, booting from an
emulated floppy no longer works.

Using bisection, I have determined that the problem appeared
with the following commit:

  commit 582299336879504353e60c7937fbc70fea93f3da
  Author: Julien Grall <email address hidden>
  Date: Wed Sep 19 12:50:09 2012 +0100

      hw/dma.c: Replace register_ioport_*

      Replace all register_ioport_*() with the new Memory API functions.
      This permits to use the new Memory stuff like listeners.

      Signed-off-by: Julien Grall <email address hidden>
      Acked-by: Avi Kivity <email address hidden>
      [AF: Rebased onto hwaddr]
      Signed-off-by: Andreas Färber <email address hidden>

One way to reproduce the problem is using the FreeDOS floppy image
listed on http://wiki.qemu.org/Testing, by running

  wget http://odin.fdos.org/odin2005/odin1440.img
  qemu-system-i386 -fda odin1440.img

This successfully boots FreeDOS in qemu version
258711c6448c44b60b0fecef1d3b09c71e23e304, but not
in version 582299336879504353e60c7937fbc70fea93f3da
or newer.

[Stefan Hajnoczi (stefanha)]

On Wed, Dec 19, 2012 at 12:09:21PM +0000, Julien Grall wrote:
> The commit 582299336879504353e60c7937fbc70fea93f3da introduced a 1-shift for
> some offset in dma emulation.
>
> Before the previous commit, which converted ioport_register_* to MemoryRegion,
> the DMA controller registered 8 ioports with the following formula:
> base + ((8 + i) << d->shift) where 0 <= i < 8
> When an IO occured within a Memory Region, DMA callback receives an offset
> relative to the started address. Here the started address is:
> base + (8 << d->shift).
> The offset should be: (i << d->shift). After the shift is reverted, the offset
> are 0..7 not 1..8.
>
> Cc: <email address hidden>
> Reviewed-by: Andreas Färber <email address hidden>
> Reported-by: Andreas Gustafsson <email address hidden>
> Signed-off-by: Julien Grall <email address hidden>
> ---
>
> Modification between V1 and V2:
> * Modify the commit message to explain the problem.
>
> hw/dma.c | 22 +++++++++++-----------
> 1 file changed, 11 insertions(+), 11 deletions(-)

This patch resolves "dma: unknown iport 0" warnings for my Windows 8 guest.

Tested-by: Stefan Hajnoczi <email address hidden>