VFIO updates for v5.5-rc1

- Remove hugepage checks for reserved pfns (Ben Luo)
 
  - Fix irq-bypass unregister ordering (Jiang Yi)
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Merge tag 'vfio-v5.5-rc1' of git://github.com/awilliam/linux-vfio

Pull VFIO updates from Alex Williamson:

 - Remove hugepage checks for reserved pfns (Ben Luo)

 - Fix irq-bypass unregister ordering (Jiang Yi)

* tag 'vfio-v5.5-rc1' of git://github.com/awilliam/linux-vfio:
  vfio/pci: call irq_bypass_unregister_producer() before freeing irq
  vfio/type1: remove hugepage checks in is_invalid_reserved_pfn()

drivers/vfio/pci/vfio_pci_intrs.c

@@ -294,8 +294,8 @@ static int vfio_msi_set_vector_signal(struct vfio_pci_device *vdev,
 	irq = pci_irq_vector(pdev, vector);
 
 	if (vdev->ctx[vector].trigger) {
-		free_irq(irq, vdev->ctx[vector].trigger);
 		irq_bypass_unregister_producer(&vdev->ctx[vector].producer);
+		free_irq(irq, vdev->ctx[vector].trigger);
 		kfree(vdev->ctx[vector].name);
 		eventfd_ctx_put(vdev->ctx[vector].trigger);
 		vdev->ctx[vector].trigger = NULL;

drivers/vfio/vfio_iommu_type1.c

@@ -294,31 +294,13 @@ static int vfio_lock_acct(struct vfio_dma *dma, long npage, bool async)
  * Some mappings aren't backed by a struct page, for example an mmap'd
  * MMIO range for our own or another device.  These use a different
  * pfn conversion and shouldn't be tracked as locked pages.
+ * For compound pages, any driver that sets the reserved bit in head
+ * page needs to set the reserved bit in all subpages to be safe.
  */
 static bool is_invalid_reserved_pfn(unsigned long pfn)
 {
-	if (pfn_valid(pfn)) {
-		bool reserved;
-		struct page *tail = pfn_to_page(pfn);
-		struct page *head = compound_head(tail);
-		reserved = !!(PageReserved(head));
-		if (head != tail) {
-			/*
-			 * "head" is not a dangling pointer
-			 * (compound_head takes care of that)
-			 * but the hugepage may have been split
-			 * from under us (and we may not hold a
-			 * reference count on the head page so it can
-			 * be reused before we run PageReferenced), so
-			 * we've to check PageTail before returning
-			 * what we just read.
-			 */
-			smp_rmb();
-			if (PageTail(tail))
-				return reserved;
-		}
-		return PageReserved(tail);
-	}
+	if (pfn_valid(pfn))
+		return PageReserved(pfn_to_page(pfn));
 
 	return true;
 }