PCI: designware: Fix pci_remap_iospace() failure path

On ARM/ARM64 architectures, PCI IO ports are emulated through memory mapped
IO, by reserving a chunk of virtual address space starting at PCI_IOBASE
and by mapping the PCI host bridges memory address space driving PCI IO
cycles to it.

PCI host bridge drivers that enable downstream PCI IO cycles map the host
bridge memory address responding to PCI IO cycles to the fixed virtual
address space through the pci_remap_iospace() API.

This means that if the pci_remap_iospace() function fails, the
corresponding host bridge PCI IO resource must be considered invalid, in
that there is no way for the kernel to actually drive PCI IO transactions
if the memory addresses responding to PCI IO cycles cannot be mapped into
the CPU virtual address space.

The PCI designware host bridge driver does not remove the PCI IO resource
from the host bridge resource windows if the pci_remap_iospace() call
fails; this is an actual bug in that the PCI host bridge would consider the
PCI IO resource valid (and possibly assign it to downstream devices) even
if the kernel was not able to map the PCI host bridge memory address
driving IO cycle to the CPU virtual address space (ie pci_remap_iospace()
failures).

Fix the PCI host bridge driver pci_remap_iospace() failure path, by
destroying the PCI host bridge PCI IO resources retrieved through firmware
when the pci_remap_iospace() function call fails, therefore preventing the
kernel from adding the respective PCI IO resource to the list of PCI host
bridge valid resources, fixing the issue.

Fixes: cbce7900 ("PCI: designware: Make driver arch-agnostic")
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
CC: Jingoo Han <jingoohan1@gmail.com>
CC: Pratyush Anand <pratyush.anand@gmail.com>

drivers/pci/host/pcie-designware.c

@@ -436,7 +436,7 @@ int dw_pcie_host_init(struct pcie_port *pp)
 	struct resource *cfg_res;
 	int i, ret;
 	LIST_HEAD(res);
-	struct resource_entry *win;
+	struct resource_entry *win, *tmp;
 
 	cfg_res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "config");
 	if (cfg_res) {
@@ -457,17 +457,20 @@ int dw_pcie_host_init(struct pcie_port *pp)
 		goto error;
 
 	/* Get the I/O and memory ranges from DT */
-	resource_list_for_each_entry(win, &res) {
+	resource_list_for_each_entry_safe(win, tmp, &res) {
 		switch (resource_type(win->res)) {
 		case IORESOURCE_IO:
+			ret = pci_remap_iospace(win->res, pp->io_base);
+			if (ret) {
+				dev_warn(pp->dev, "error %d: failed to map resource %pR\n",
+					 ret, win->res);
+				resource_list_destroy_entry(win);
+			} else {
 				pp->io = win->res;
 				pp->io->name = "I/O";
 				pp->io_size = resource_size(pp->io);
 				pp->io_bus_addr = pp->io->start - win->offset;
-			ret = pci_remap_iospace(pp->io, pp->io_base);
-			if (ret)
-				dev_warn(pp->dev, "error %d: failed to map resource %pR\n",
-					 ret, pp->io);
+			}
 			break;
 		case IORESOURCE_MEM:
 			pp->mem = win->res;