[patch RFC 23/38] x86/xen: Rework MSI teardown

[Thomas Gleixner <tglx@xxxxxxxxxxxxx>]

X86 cannot store the irq domain pointer in struct device without breaking
XEN because the irq domain pointer takes precedence over arch_*_msi_irqs()
fallbacks.

XENs MSI teardown relies on default_teardown_msi_irqs() which invokes
arch_teardown_msi_irq(). default_teardown_msi_irqs() is a trivial iterator
over the msi entries associated to a device.

Implement this loop in xen_teardown_msi_irqs() to prepare for removal of
the fallbacks for X86.

This is a preparatory step to wrap XEN MSI alloc/free into a irq domain
which in turn allows to store the irq domain pointer in struct device and
to use the irq domain functions directly.

Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
---
 arch/x86/pci/xen.c |   23 ++++++++++++++++++-----
 1 file changed, 18 insertions(+), 5 deletions(-)

--- a/arch/x86/pci/xen.c
+++ b/arch/x86/pci/xen.c
@@ -376,20 +376,31 @@ static void xen_initdom_restore_msi_irqs
 static void xen_teardown_msi_irqs(struct pci_dev *dev)
 {
        struct msi_desc *msidesc;
+       int i;
+
+       for_each_pci_msi_entry(msidesc, dev) {
+               if (msidesc->irq) {
+                       for (i = 0; i < msidesc->nvec_used; i++)
+                               xen_destroy_irq(msidesc->irq + i);
+               }
+       }
+}
+
+static void xen_pv_teardown_msi_irqs(struct pci_dev *dev)
+{
+       struct msi_desc *msidesc = first_pci_msi_entry(dev);
 
-       msidesc = first_pci_msi_entry(dev);
        if (msidesc->msi_attrib.is_msix)
                xen_pci_frontend_disable_msix(dev);
        else
                xen_pci_frontend_disable_msi(dev);
 
-       /* Free the IRQ's and the msidesc using the generic code. */
-       default_teardown_msi_irqs(dev);
+       xen_teardown_msi_irqs(dev);
 }
 
 static void xen_teardown_msi_irq(unsigned int irq)
 {
-       xen_destroy_irq(irq);
+       WARN_ON_ONCE(1);
 }
 
 #endif
@@ -412,7 +423,7 @@ int __init pci_xen_init(void)
 #ifdef CONFIG_PCI_MSI
        x86_msi.setup_msi_irqs = xen_setup_msi_irqs;
        x86_msi.teardown_msi_irq = xen_teardown_msi_irq;
-       x86_msi.teardown_msi_irqs = xen_teardown_msi_irqs;
+       x86_msi.teardown_msi_irqs = xen_pv_teardown_msi_irqs;
        pci_msi_ignore_mask = 1;
 #endif
        return 0;
@@ -436,6 +447,7 @@ static void __init xen_hvm_msi_init(void
        }
 
        x86_msi.setup_msi_irqs = xen_hvm_setup_msi_irqs;
+       x86_msi.teardown_msi_irqs = xen_teardown_msi_irqs;
        x86_msi.teardown_msi_irq = xen_teardown_msi_irq;
 }
 #endif
@@ -472,6 +484,7 @@ int __init pci_xen_initial_domain(void)
 #ifdef CONFIG_PCI_MSI
        x86_msi.setup_msi_irqs = xen_initdom_setup_msi_irqs;
        x86_msi.teardown_msi_irq = xen_teardown_msi_irq;
+       x86_msi.teardown_msi_irqs = xen_teardown_msi_irqs;
        x86_msi.restore_msi_irqs = xen_initdom_restore_msi_irqs;
        pci_msi_ignore_mask = 1;
 #endif