On 12/08/14 08:25, Yijing Wang wrote:

Commit 0e4ccb150 added two __weak arch functions arch_msix_mask_irq()
and arch_msi_mask_irq() to fix a bug found when running xen in x86.
Introduced these two funcntions make MSI code complex. This patch
reverted commit 0e4ccb150 and add #ifdef for x86 msi_chip to fix this
bug for simplicity. Also this is preparation for using struct
msi_chip instead of weak arch MSI functions in all platforms.

[...]

 static struct irq_chip msi_chip = {
 	.name			= "PCI-MSI",
+#ifdef CONFIG_XEN
+	.irq_unmask		= nop_unmask_msi_irq,
+	.irq_mask		= nop_mask_msi_irq,
+#else
 	.irq_unmask		= unmask_msi_irq,
 	.irq_mask		= mask_msi_irq,
+#endif

No.  CONFIG_XEN kernels can run on Xen and bare metal so this must be a
runtime option.

David