Re: [Qemu-devel] r6677 broke access to physical FDD on Win32

[Luca Tettamanti <kronos.it@gmail.com>]

[-- Attachment #1: Type: text/plain, Size: 1789 bytes --]

On Fri, Mar 20, 2009 at 11:01 PM, Anthony Liguori <anthony@codemonkey.ws> wrote:
> Robert Riebisch wrote:
>>
>> Hi!
>>
>> If I run QEMU on Win32 with option "-fda a:", then I'm unable to access
>> physical floppies from guest OS. "Physical" also includes virtual drives
>> created by <http://chitchat.at.infoseek.co.jp/vmware/vfd.html>.
>>
>> I'm also unable to boot such floppies ("-boot a"). Error message is:
>> "Boot failed: not a bootable floppy disk"
>>
>> By doing some builds I narrowed the problem down to
>> <http://svn.savannah.gnu.org/viewvc?view=rev&root=qemu&revision=6677> by
>> Anthony Liguori.
>>
>
> I suspect this code:
>
> block-raw-win32.c:raw_getlength():
>
>   case FTYPE_HARDDISK:
>       status = DeviceIoControl(s->hfile, IOCTL_DISK_GET_DRIVE_GEOMETRY_EX,
>                                NULL, 0, &dg, sizeof(dg), &count, NULL);
>       if (status != 0) {
>           l = dg.DiskSize;
>       }
>       break;
>
> Is not doing the correct thing.

Sort of; the real problem is in find_device_type(), it thinks that the
device is a file :S

The bug is here:
  type = GetDriveType(s->drive_path);
  if (type == DRIVE_CDROM)
    return FTYPE_CD;
  else
    return FTYPE_FILE;

GetDriveType("a:") returns DRIVE_REMOVABLE, which according to MSDN
means "The drive has removable media; for example, a floppy drive,
thumb drive, or flash card reader."; the code is not expecting such a
value so it sets the type to FTYPE_FILE; raw_getlength() then uses
GetFileSize() which of course fails...

Here's a patch for properly handling the return value of GetDriveType
(sorry for the attachment, but I'm currently using a remote VM over
RDP and don't have a decent mailer installed).

Luca

[-- Attachment #2: fix-fda.diff --]
[-- Type: application/octet-stream, Size: 856 bytes --]

Fix find_device_type() to correctly identify floppy disk devices;
they are reported as DRIVE_REMOVABLE by win32.

Signed-off-by: Luca Tettamanti

diff --git a/block-raw-win32.c b/block-raw-win32.c
index d034b4a..ba9b0cf 100644
--- a/block-raw-win32.c
+++ b/block-raw-win32.c
@@ -408,10 +408,15 @@ static int find_device_type(BlockDriverState *bs, const char *filename)
             return FTYPE_HARDDISK;
         snprintf(s->drive_path, sizeof(s->drive_path), "%c:\\", p[0]);
         type = GetDriveType(s->drive_path);
-        if (type == DRIVE_CDROM)
+        switch (type) {
+        case DRIVE_REMOVABLE:
+        case DRIVE_FIXED:
+            return FTYPE_HARDDISK;
+        case DRIVE_CDROM:
             return FTYPE_CD;
-        else
+        default:
             return FTYPE_FILE;
+        }
     } else {
         return FTYPE_FILE;
     }