[pve-devel] ahci: properly reset PxCMD on HBA reset -> patch

Alexandre DERUMIER aderumier at odiso.com
Fri Aug 31 14:04:40 CEST 2012

----- Mail transféré ----- 

De: "Jason Baron" <jbaron at redhat.com> 
À: agraf at suse.de 
Cc: kwolf at redhat.com, aliguori at us.ibm.com, mst at redhat.com, qemu-devel at nongnu.org, "jan kiszka" <jan.kiszka at siemens.com>, armbru at redhat.com, lcapitulino at redhat.com, yamahata at valinux.co.jp, "alex williamson" <alex.williamson at redhat.com>, pbonzini at redhat.com, afaerber at suse.de 
Envoyé: Jeudi 23 Août 2012 23:09:25 
Objet: [Qemu-devel] [PATCH] ahci: properly reset PxCMD on HBA reset 

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. 

Signed-off-by: Jason Baron <jbaron at 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); 




Alexandre D e rumier 

Ingénieur Systèmes et Réseaux 

Fixe : 03 20 68 88 85 

Fax : 03 20 68 90 88 

45 Bvd du Général Leclerc 59100 Roubaix 
12 rue Marivaux 75002 Paris 

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