ahci: MSI capability should be at 0x80, not 0x50.

In the Intel ICH9 data sheet, the MSI capability offset
in the PCI configuration space for ICH9 AHCI devices is
specified to be 0x80.

Further, the PCI capability pointer should always point
to 0x80 in ICH9 devices, despite the fact that AHCI 1.3
specifies that it should be pointing to PMCAP (Which in
this instance would be 0x70) to maintain adherence to
the Intel data sheet specifications and real observed behavior.
Signed-off-by: NJohn Snow <jsnow@redhat.com>
Message-id: 1408643079-30675-3-git-send-email-jsnow@redhat.com
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>

hw/ide/ich.c

@@ -71,6 +71,7 @@
 #include <hw/ide/pci.h>
 #include <hw/ide/ahci.h>
 
+#define ICH9_MSI_CAP_OFFSET     0x80
 #define ICH9_SATA_CAP_OFFSET    0xA8
 
 #define ICH9_IDP_BAR            4
@@ -115,7 +116,6 @@ static int pci_ich9_ahci_init(PCIDevice *dev)
     /* XXX Software should program this register */
     dev->config[0x90]   = 1 << 6; /* Address Map Register - AHCI mode */
 
-    msi_init(dev, 0x50, 1, true, false);
     d->ahci.irq = pci_allocate_irq(dev);
 
     pci_register_bar(dev, ICH9_IDP_BAR, PCI_BASE_ADDRESS_SPACE_IO,
@@ -135,6 +135,11 @@ static int pci_ich9_ahci_init(PCIDevice *dev)
                  (ICH9_IDP_BAR + 0x4) | (ICH9_IDP_INDEX_LOG2 << 4));
     d->ahci.idp_offset = ICH9_IDP_INDEX;
 
+    /* Although the AHCI 1.3 specification states that the first capability
+     * should be PMCAP, the Intel ICH9 data sheet specifies that the ICH9
+     * AHCI device puts the MSI capability first, pointing to 0x80. */
+    msi_init(dev, ICH9_MSI_CAP_OFFSET, 1, true, false);
+
     return 0;
 }