From: Marcus Barrow <mbarrow@redhat.com>
Date: Sat, 25 Oct 2008 21:52:13 -0400
Subject: [scsi] qla2xxx: restore disable by default of MSI, MSI-X
Message-id: 20081026015213.14145.54472.sendpatchset@file.bos.redhat.com
O-Subject: [rhel 5.3 bug] qla2xxx - restore disable by default of MSI, MSI-X
Bugzilla: 468555
RH-Acked-by: Tomas Henzl <thenzl@redhat.com>

BZ 468555 - qla2xxx - restore disable by default of MSI, MSI-X.

When support for the FCoE adapters was added the default behavior of having MSI
and MSIX interrupt handling disabled was removed.

IBM's testing of the MRG product has shown problems under load, which were
resolved by disabling MSI and MSI-X. This is described in: BZ 466903 - mailbox
timeouts observed on ds4700 luns.

This patch disables these interrupt handling mechanisms by default. MSI and
MSI-X can be enabled by the module parameter "ql2xenablemsix=1".

This applies and builds cleanly with 2.6.18-120 and causes use of legacy pci
interrupts by default.

diff --git a/drivers/scsi/qla2xxx/qla_isr.c b/drivers/scsi/qla2xxx/qla_isr.c
index f5bb36d..5840c2f 100644
--- a/drivers/scsi/qla2xxx/qla_isr.c
+++ b/drivers/scsi/qla2xxx/qla_isr.c
@@ -1894,8 +1894,9 @@ qla2x00_request_irqs(scsi_qla_host_t *ha)
 	int ret;
 
 	/* If possible, enable MSI-X. */
-	if (!IS_QLA2432(ha) && !IS_QLA2532(ha) && !IS_QLA8432(ha))
-		goto skip_msix;
+	if ((!IS_QLA2432(ha) && !IS_QLA2532(ha) && !IS_QLA8432(ha))
+	    || !ql2xenablemsix)
+		goto skip_msi;
 
 	if (IS_QLA2432(ha) && (ha->chip_revision < QLA_MSIX_CHIP_REV_24XX ||
 	    !QLA_MSIX_FW_MODE_1(ha->fw_attributes))) {
@@ -1926,17 +1927,15 @@ qla2x00_request_irqs(scsi_qla_host_t *ha)
 	}
 	qla_printk(KERN_WARNING, ha,
 	    "MSI-X: Falling back-to INTa mode -- %d.\n", ret);
-skip_msix:
-	if (!IS_QLA24XX(ha) && !IS_QLA2532(ha) && !IS_QLA8432(ha))
-		goto skip_msi;
 
+skip_msix:
 	ret = pci_enable_msi(ha->pdev);
 	if (!ret) {
 		DEBUG2(qla_printk(KERN_INFO, ha, "MSI: Enabled.\n"));
 		ha->flags.msi_enabled = 1;
 	}
-skip_msi:
 
+skip_msi:
 	ret = request_irq(ha->pdev->irq, ha->isp_ops->intr_handler,
 	    IRQF_DISABLED|IRQF_SHARED, QLA2XXX_DRIVER_NAME, ha);
 	if (!ret) {