nvidia: make Resizable BAR resize failure non-fatal, and skip proactively on Thunderbolt

kernel-open/conftest.sh

@@ -4067,6 +4067,23 @@ compile_test() {
             compile_check_conftest "$CODE" "NV_PCI_REBAR_GET_POSSIBLE_SIZES_PRESENT" "" "functions"
         ;;
 
+        pci_is_thunderbolt_attached)
+            #
+            # Determine if the pci_is_thunderbolt_attached() function is
+            # present.
+            #
+            # Added by commit 0d4ef7ce7e78 ("PCI: Identify Thunderbolt
+            # devices") in v4.15.
+            #
+            CODE="
+            #include <linux/pci.h>
+            void conftest_pci_is_thunderbolt_attached(void) {
+                pci_is_thunderbolt_attached();
+            }"
+
+            compile_check_conftest "$CODE" "NV_PCI_IS_THUNDERBOLT_ATTACHED_PRESENT" "" "functions"
+        ;;
+
         pci_resize_resource_has_exclude_bars_arg)
             #
             # Determine if pci_resize_resource() has exclude_bars argument.

kernel-open/nvidia/nv-pci.c

@@ -208,6 +208,25 @@ static int nv_resize_pcie_bars(struct pci_dev *pci_dev) {
         return 0;
     }
 
+#if defined(NV_PCI_IS_THUNDERBOLT_ATTACHED_PRESENT)
+    /*
+     * Thunderbolt / USB4 hotplug bridges have a small prefetchable MMIO
+     * window that cannot accommodate a GiB-scale resized BAR.  Skip
+     * the resize attempt proactively rather than trying and failing,
+     * which avoids an uninformative -ENOENT in the kernel log and
+     * sidesteps the failure path entirely.
+     */
+    if (pci_is_thunderbolt_attached(pci_dev))
+    {
+        nv_printf(NV_DBG_INFO,
+                  "NVRM: %04x:%02x:%02x.%x: device is downstream of Thunderbolt, "
+                  "skipping BAR1 resize\n",
+                  NV_PCI_DOMAIN_NUMBER(pci_dev), NV_PCI_BUS_NUMBER(pci_dev),
+                  NV_PCI_SLOT_NUMBER(pci_dev), PCI_FUNC(pci_dev->devfn));
+        return 0;
+    }
+#endif
+
     // Check if BAR1 has PCIe rebar capabilities
     sizes = pci_rebar_get_possible_sizes(pci_dev, NV_GPU_BAR1);
     if (sizes == 0) {
@@ -1949,9 +1968,18 @@ nv_pci_probe
         goto err_zero_dev;
 
     if (nv_resize_pcie_bars(pci_dev)) {
-        nv_printf(NV_DBG_ERRORS,
-            "NVRM: Fatal Error while attempting to resize PCIe BARs.\n");
-        goto err_zero_dev;
+        /*
+         * Resizable BAR is an enhancement, not a requirement.  When
+         * the resize fails (commonly because the upstream bridge
+         * prefetchable window is too small to accommodate a GiB-scale
+         * BAR, as seen with Thunderbolt/USB4 hotplug bridges), the
+         * device is still functional with its existing BAR
+         * allocation.  Do not turn a minor performance degradation
+         * into a hard probe failure -- log a warning and continue.
+         */
+        nv_printf(NV_DBG_WARNINGS,
+            "NVRM: PCIe BAR resize failed; continuing with the existing "
+            "BAR allocation.\n");
     }
 
     nvl->all_mappings_revoked = NV_TRUE;

kernel-open/nvidia/nvidia.Kbuild

@@ -120,6 +120,7 @@ NV_CONFTEST_FUNCTION_COMPILE_TESTS += pde_data
 NV_CONFTEST_FUNCTION_COMPILE_TESTS += xen_ioemu_inject_msi
 NV_CONFTEST_FUNCTION_COMPILE_TESTS += phys_to_dma
 NV_CONFTEST_FUNCTION_COMPILE_TESTS += pci_rebar_get_possible_sizes
+NV_CONFTEST_FUNCTION_COMPILE_TESTS += pci_is_thunderbolt_attached
 NV_CONFTEST_FUNCTION_COMPILE_TESTS += get_backlight_device_by_name
 NV_CONFTEST_FUNCTION_COMPILE_TESTS += dma_direct_map_resource
 NV_CONFTEST_FUNCTION_COMPILE_TESTS += flush_cache_all