Re: [Qemu-devel] [PATCH] ahci: properly reset PxCMD on HBA reset

[Jason Baron]

On Fri, Aug 24, 2012 at 06:39:02AM +0200, Alexander Graf wrote:
> > While testing q35, I found that windows 7 (specifically, windows 7 ultimate
> > with sp1 x64), wouldn't install because it can't find the cdrom or disk 
> > drive.
> > The failure message is: 'A required cd/dvd device driver is missing. If you
> > have a driver floppy disk, CD, DVD, or USB flash drive, please insert it 
> > now.'
> > This can also be reproduced on piix by adding an ahci controller, and
> > observing that windows 7 does not see any devices behind it.
> > 
> > The problem is that when windows issues a HBA reset, qemu does not reset the
> > individual ports' PxCMD register. Windows 7 then reads back the PxCMD 
> > register
> > and presumably assumes that the ahci controller has already been 
> > initialized.
> > Windows then never sets up the PxIE register to enable interrupts, and thus 
> > it
> > never gets irqs back when it sends ata device inquiry commands.
> > 
> > I believe this change brings qemu into ahci 1.3 specification compliance.
> > 
> > Section 10.4.3 HBA Reset:
> > 
> > "
> > When GHC.HR is set to '1', GHC.AE, GHC.IE, the IS register, and all port
> > register fields (except PxFB/PxFBU/PxCLB/PxCLBU) that are not HwInit in the
> > HBA's register memory space are reset.
> > "
> > 
> > I've also re-tested Fedora 16 and 17 to verify that they continue to work 
> > with
> > this change.
> 
> What a nasty little bug. If it makes it work for you, the change is all fine 
> from my POV (and should go into 1.2).
> 

Ok, I don't see it 1.2.0-rc2. If others are ok with this for 1.2, whose
tree should this go through?

Thanks,

-Jason