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

From: Alexander Graf <agraf@suse.de>
To: Luiz Capitulino <lcapitulino@redhat.com>
Cc: "kwolf@redhat.com" <kwolf@redhat.com>,
	"aliguori@us.ibm.com" <aliguori@us.ibm.com>,
	"mst@redhat.com" <mst@redhat.com>,
	"jan.kiszka@siemens.com" <jan.kiszka@siemens.com>,
	Jason Baron <jbaron@redhat.com>,
	"armbru@redhat.com" <armbru@redhat.com>,
	"qemu-devel@nongnu.org" <qemu-devel@nongnu.org>,
	"yamahata@valinux.co.jp" <yamahata@valinux.co.jp>,
	"alex.williamson@redhat.com" <alex.williamson@redhat.com>,
	"pbonzini@redhat.com" <pbonzini@redhat.com>,
	"afaerber@suse.de" <afaerber@suse.de>
Subject: Re: [Qemu-devel] [PATCH] ahci: properly reset PxCMD on HBA reset
Date: Fri, 24 Aug 2012 07:34:51 -0700	[thread overview]
Message-ID: <C51C6D1A-AACE-4720-8A15-C9EC433D4810@suse.de> (raw)
In-Reply-To: <20120824111825.06484dd4@doriath.home>

Am 24.08.2012 um 07:18 schrieb Luiz Capitulino <lcapitulino@redhat.com>:

> On Thu, 23 Aug 2012 17:09:25 -0400
> Jason Baron <jbaron@redhat.com> 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.

Alex

> 
>> 
>> 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 <jbaron@redhat.com>
>> ---
>> 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);
>>     }
>> }
> 