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

[Luiz Capitulino]

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.

> 
> 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.
> 
> Signed-off-by: Jason Baron <address@hidden>
> ---
>  hw/ide/ahci.c |    1 +
>  1 files changed, 1 insertions(+), 0 deletions(-)
> 
> diff --git a/hw/ide/ahci.c b/hw/ide/ahci.c
> index 9fe89a5..06c236f 100644
> --- a/hw/ide/ahci.c
> +++ b/hw/ide/ahci.c
> @@ -1199,6 +1199,7 @@ void ahci_reset(AHCIState *s)
>          pr->irq_stat = 0;
>          pr->irq_mask = 0;
>          pr->scr_ctl = 0;
> +        pr->cmd = 0;
>          ahci_reset_port(s, i);
>      }
>  }