PCI: Ignore requested alignment for PROBE_ONLY and fixed resources

Users may request additional alignment of PCI resources, e.g., to align
BARs on page boundaries so they can be shared with guests via VFIO.  This
of course may require reallocation if firmware has already assigned the
BARs with smaller alignments.

If the platform has requested PCI_PROBE_ONLY, we should never change any
PCI BARs, so we can't provide any additional alignment.  Also, if a BAR is
marked as IORESOURCE_PCI_FIXED, e.g., for PCI Enhanced Allocation or if the
firmware depends on the current BAR value, we can't change the alignment.

In these cases, log a message and ignore the user's alignment requests.

[bhelgaas: changelog, use goto to simplify PCI_PROBE_ONLY check]
Signed-off-by: Yongji Xie <xyjxie@linux.vnet.ibm.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

drivers/pci/pci.c

@@ -4959,6 +4959,13 @@ static resource_size_t pci_specified_resource_alignment(struct pci_dev *dev)
 
 	spin_lock(&resource_alignment_lock);
 	p = resource_alignment_param;
+	if (!*p)
+		goto out;
+	if (pci_has_flag(PCI_PROBE_ONLY)) {
+		pr_info_once("PCI: Ignoring requested alignments (PCI_PROBE_ONLY)\n");
+		goto out;
+	}
+
 	while (*p) {
 		count = 0;
 		if (sscanf(p, "%d%n", &align_order, &count) == 1 &&
@@ -5023,6 +5030,7 @@ static resource_size_t pci_specified_resource_alignment(struct pci_dev *dev)
 		}
 		p++;
 	}
+out:
 	spin_unlock(&resource_alignment_lock);
 	return align;
 }
@@ -5063,6 +5071,12 @@ void pci_reassigndev_resource_alignment(struct pci_dev *dev)
 		r = &dev->resource[i];
 		if (!(r->flags & IORESOURCE_MEM))
 			continue;
+		if (r->flags & IORESOURCE_PCI_FIXED) {
+			dev_info(&dev->dev, "Ignoring requested alignment for BAR%d: %pR\n",
+				i, r);
+			continue;
+		}
+
 		size = resource_size(r);
 		if (size < align) {
 			size = align;