PCI/MSI: Switch msix_capability_init() to guard(msi_desc_lock)

Split the lock protected functionality of msix_capability_init() out into a
helper function and use guard(msi_desc_lock) to replace the lock/unlock
pair.

Simplify the error path in the helper function by utilizing a custom
cleanup to get rid of the remaining gotos.

No functional change intended.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Link: https://lore.kernel.org/all/20250319105506.564105011@linutronix.de

Author: KAGA-KOKO

drivers/pci/msi/msi.c

@@ -660,35 +660,39 @@ static void msix_mask_all(void __iomem *base, int tsize)
 		writel(ctrl, base + PCI_MSIX_ENTRY_VECTOR_CTRL);
 }
 
-static int msix_setup_interrupts(struct pci_dev *dev, struct msix_entry *entries,
-				 int nvec, struct irq_affinity *affd)
+DEFINE_FREE(free_msi_irqs, struct pci_dev *, if (_T) pci_free_msi_irqs(_T));
+
+static int __msix_setup_interrupts(struct pci_dev *__dev, struct msix_entry *entries,
+				   int nvec, struct irq_affinity_desc *masks)
 {
-	struct irq_affinity_desc *masks __free(kfree) =
-		affd ? irq_create_affinity_masks(nvec, affd) : NULL;
-	int ret;
+	struct pci_dev *dev __free(free_msi_irqs) = __dev;
 
-	msi_lock_descs(&dev->dev);
-	ret = msix_setup_msi_descs(dev, entries, nvec, masks);
+	int ret = msix_setup_msi_descs(dev, entries, nvec, masks);
 	if (ret)
-		goto out_free;
+		return ret;
 
 	ret = pci_msi_setup_msi_irqs(dev, nvec, PCI_CAP_ID_MSIX);
 	if (ret)
-		goto out_free;
+		return ret;
 
 	/* Check if all MSI entries honor device restrictions */
 	ret = msi_verify_entries(dev);
 	if (ret)
-		goto out_free;
+		return ret;
 
 	msix_update_entries(dev, entries);
-	goto out_unlock;
+	retain_and_null_ptr(dev);
+	return 0;
+}
 
-out_free:
-	pci_free_msi_irqs(dev);
-out_unlock:
-	msi_unlock_descs(&dev->dev);
-	return ret;
+static int msix_setup_interrupts(struct pci_dev *dev, struct msix_entry *entries,
+				 int nvec, struct irq_affinity *affd)
+{
+	struct irq_affinity_desc *masks __free(kfree) =
+		affd ? irq_create_affinity_masks(nvec, affd) : NULL;
+
+	guard(msi_descs_lock)(&dev->dev);
+	return __msix_setup_interrupts(dev, entries, nvec, masks);
 }
 
 /**