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

[Luiz Capitulino]

On Fri, 24 Aug 2012 07:34:51 -0700
Alexander Graf <address@hidden> wrote:

> 
> 
> Am 24.08.2012 um 07:18 schrieb Luiz Capitulino <address@hidden>:
> 
> > On Thu, 23 Aug 2012 17:09:25 -0400
> > Jason Baron <address@hidden> 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.
> > 
> > I've tested this but unfortunately it doesn't fix the issues I'm getting 
> > with
> > OpenBSD 5.1 and NetBSD 5.1 as reported here (section 'master with ahci'):
> > 
> > http://lists.gnu.org/archive/html/qemu-devel/2012-08/msg03329.html
> > 
> > PS: Those could be kernel issues, of course.
> 
> The BSDs already fail in detecting the cotroller as a whole, right? Not just 
> disks on it.

Thanks for the clarification. Didn't try to understand the patch, automatically
thought it could be related to my last testing report.