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[Qemu-devel] Re: SeaBIOS cdrom regression with Vista

From: Kevin O'Connor
Subject: [Qemu-devel] Re: SeaBIOS cdrom regression with Vista
Date: Fri, 20 Nov 2009 14:08:03 -0500
User-agent: Mutt/1.5.19 (2009-01-05)

On Fri, Nov 20, 2009 at 01:03:51PM -0500, Kevin O'Connor wrote:
> I've looked into this, and it looks like the cdrom is left in an odd
> state.  At this point, I think SeaBIOS is tickling a bug outside of
> seabios (eg, in Vista or qemu).  I would appreciate it someone with
> cdrom knowledge of qemu could help.
> SeaBIOS has a different ata drive detection mechanism than bochs - it
> needs it in order to work on real hardware.  So, this explains why
> bochs bios doesn't show this issue.  (Seabios tries to send an
> "identify packet device" and then an "identify device" command to
> detect a drive; bochs bios looks for a signature in the ata registers
> after an ata reset.)

It looks like I spoke too soon.  It appears the SeaBIOS init can leave
the ATA controller in an interrupts disabled state.  This appears to
confuse Vista.  So, this is a SeaBIOS bug - I'll implement a fix.

The patch below enables Vista to see the cdrom (though, it's not a
real fix).


--- a/src/ata.c
+++ b/src/ata.c
@@ -237,6 +237,7 @@ send_cmd(struct drive_s *drive_g, struct ata_pio_command 
         return -4;
     if (!(status & ATA_CB_STAT_DRQ)) {
+    outb(ATA_CB_DC_HD15, iobase2+ATA_CB_DC);
         dprintf(6, "send_cmd : DRQ not set (status %02x)\n", status);
         return -5;

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