x86/pci/xen: populate MSI sysfs entries

Commit bf5e758 ("genirq/msi: Simplify sysfs handling") reworked the
creation of sysfs entries for MSI IRQs. The creation used to be in
msi_domain_alloc_irqs_descs_locked after calling ops->domain_alloc_irqs.
Then it moved into __msi_domain_alloc_irqs which is an implementation of
domain_alloc_irqs. However, Xen comes with the only other implementation
of domain_alloc_irqs and hence doesn't run the sysfs population code
anymore.

Commit 6c79699 ("x86/pci/xen: Fixup fallout from the PCI/MSI
overhaul") set the flag MSI_FLAG_DEV_SYSFS for the xen msi_domain_info
but that doesn't actually have an effect because Xen uses it's own
domain_alloc_irqs implementation.

Fix this by making use of the fallback functions for sysfs population.

Fixes: bf5e758 ("genirq/msi: Simplify sysfs handling")
Signed-off-by: Maximilian Heyne <mheyne@amazon.de>
Reviewed-by: Juergen Gross <jgross@suse.com>
Link: https://lore.kernel.org/r/20230503131656.15928-1-mheyne@amazon.de
Signed-off-by: Juergen Gross <jgross@suse.com>

arch/x86/pci/xen.c

@@ -198,7 +198,7 @@ static int xen_setup_msi_irqs(struct pci_dev *dev, int nvec, int type)
 		i++;
 	}
 	kfree(v);
-	return 0;
+	return msi_device_populate_sysfs(&dev->dev);
 
 error:
 	if (ret == -ENOSYS)
@@ -254,7 +254,7 @@ static int xen_hvm_setup_msi_irqs(struct pci_dev *dev, int nvec, int type)
 		dev_dbg(&dev->dev,
 			"xen: msi --> pirq=%d --> irq=%d\n", pirq, irq);
 	}
-	return 0;
+	return msi_device_populate_sysfs(&dev->dev);
 
 error:
 	dev_err(&dev->dev, "Failed to create MSI%s! ret=%d!\n",
@@ -346,7 +346,7 @@ static int xen_initdom_setup_msi_irqs(struct pci_dev *dev, int nvec, int type)
 		if (ret < 0)
 			goto out;
 	}
-	ret = 0;
+	ret = msi_device_populate_sysfs(&dev->dev);
 out:
 	return ret;
 }
@@ -394,6 +394,8 @@ static void xen_teardown_msi_irqs(struct pci_dev *dev)
 			xen_destroy_irq(msidesc->irq + i);
 		msidesc->irq = 0;
 	}
+
+	msi_device_destroy_sysfs(&dev->dev);
 }
 
 static void xen_pv_teardown_msi_irqs(struct pci_dev *dev)

include/linux/msi.h

@@ -383,14 +383,21 @@ int arch_setup_msi_irq(struct pci_dev *dev, struct msi_desc *desc);
 void arch_teardown_msi_irq(unsigned int irq);
 int arch_setup_msi_irqs(struct pci_dev *dev, int nvec, int type);
 void arch_teardown_msi_irqs(struct pci_dev *dev);
+#endif /* CONFIG_PCI_MSI_ARCH_FALLBACKS */
+
+/*
+ * Xen uses non-default msi_domain_ops and hence needs a way to populate sysfs
+ * entries of MSI IRQs.
+ */
+#if defined(CONFIG_PCI_XEN) || defined(CONFIG_PCI_MSI_ARCH_FALLBACKS)
 #ifdef CONFIG_SYSFS
 int msi_device_populate_sysfs(struct device *dev);
 void msi_device_destroy_sysfs(struct device *dev);
 #else /* CONFIG_SYSFS */
 static inline int msi_device_populate_sysfs(struct device *dev) { return 0; }
 static inline void msi_device_destroy_sysfs(struct device *dev) { }
 #endif /* !CONFIG_SYSFS */
-#endif /* CONFIG_PCI_MSI_ARCH_FALLBACKS */
+#endif /* CONFIG_PCI_XEN || CONFIG_PCI_MSI_ARCH_FALLBACKS */
 
 /*
  * The restore hook is still available even for fully irq domain based

kernel/irq/msi.c

@@ -542,7 +542,7 @@ static int msi_sysfs_populate_desc(struct device *dev, struct msi_desc *desc)
 	return ret;
 }
 
-#ifdef CONFIG_PCI_MSI_ARCH_FALLBACKS
+#if defined(CONFIG_PCI_MSI_ARCH_FALLBACKS) || defined(CONFIG_PCI_XEN)
 /**
  * msi_device_populate_sysfs - Populate msi_irqs sysfs entries for a device
  * @dev:	The device (PCI, platform etc) which will get sysfs entries
@@ -574,7 +574,7 @@ void msi_device_destroy_sysfs(struct device *dev)
 	msi_for_each_desc(desc, dev, MSI_DESC_ALL)
 		msi_sysfs_remove_desc(dev, desc);
 }
-#endif /* CONFIG_PCI_MSI_ARCH_FALLBACK */
+#endif /* CONFIG_PCI_MSI_ARCH_FALLBACK || CONFIG_PCI_XEN */
 #else /* CONFIG_SYSFS */
 static inline int msi_sysfs_create_group(struct device *dev) { return 0; }
 static inline int msi_sysfs_populate_desc(struct device *dev, struct msi_desc *desc) { return 0; }