nv-pci-rebar.patch

--- nv-pci.c	2022-01-08 23:12:19.137095516 +0000
+++ /usr/src/nvidia-495.46/nvidia/nv-pci.c	2022-01-09 00:05:21.323360921 +0000
@@ -217,7 +217,78 @@



+#define NV_GPU_BAR1 1
+static int nv_resize_pcie_bars(struct pci_dev *pci_dev) {
+	struct pci_host_bridge *host;
+    u16 cmd;
+    int r, old_size, requested_size;
+    int ret = 0;
+
+    // Check if BAR1 has PCIe rebar capabilities
+    u32 sizes = pci_rebar_get_possible_sizes(pci_dev, NV_GPU_BAR1);
+    if (sizes == 0) {
+        /* ReBAR not available. Nothing to do. */
+        return 0;
+    }
+
+    /* Try to resize the BAR to the largest supported size */
+    requested_size = fls(sizes) - 1;
+
+	/* If the kernel will refuse us, don't even try to resize,
+       but give an informative error */
+	host = pci_find_host_bridge(pci_dev->bus);
+	if (host->preserve_config) {
+        nv_printf(NV_DBG_INFO, "NVRM: Not resizing BAR because the firmware forbids moving windows.\n");
+		return 0;
+    }
+
+    nv_printf(NV_DBG_INFO, "NVRM: %04x:%02x:%02x.%x: Attempting to resize BAR1.\n",
+        NV_PCI_DOMAIN_NUMBER(pci_dev), NV_PCI_BUS_NUMBER(pci_dev),
+        NV_PCI_SLOT_NUMBER(pci_dev), PCI_FUNC(pci_dev->devfn));
+
+    /* Disable memory decoding - required by the kernel APIs */
+	pci_read_config_word(pci_dev, PCI_COMMAND, &cmd);
+	pci_write_config_word(pci_dev, PCI_COMMAND, cmd & ~PCI_COMMAND_MEMORY);
+
+    /* Release BAR1 */
+    pci_release_resource(pci_dev, NV_GPU_BAR1);
+
+    /* Save the current size, just in case things go wrong */
+    old_size = fls(pci_resource_len(pci_dev, NV_GPU_BAR1)) >> 20;
+
+resize:
+    /* Attempt to resize BAR1 to the largest supported size */
+	r = pci_resize_resource(pci_dev, NV_GPU_BAR1, requested_size);
+
+    if (r) {
+        if (r == -ENOSPC)
+            nv_printf(NV_DBG_ERRORS, "NVRM: No address space to allocate resized BAR1.\n");
+        else if (r)
+            nv_printf(NV_DBG_ERRORS, "NVRM: BAR resizing failed with error `%d`.\n", r);
+
+        /* Re-attempt assignment of PCIe resources */
+        pci_assign_unassigned_bus_resources(pci_dev->bus);
+    }

+    if (pci_resource_flags(pci_dev, NV_GPU_BAR1) & IORESOURCE_UNSET) {
+        if (requested_size != old_size) {
+            /* Try to get the BAR back with the original size */
+            requested_size = old_size;
+            goto resize;
+        }
+        /* Something went horribly wrong and the kernel didn't manage to re-allocate BAR1.
+           This is unlikely (because we had space before), but can happen. */
+        nv_printf(NV_DBG_ERRORS, "NVRM: FATAL: Failed to re-allocate BAR1.\n");
+        ret = -ENODEV;
+        goto done;
+    }
+
+done:
+    /* Re-enable memory decoding */
+	pci_write_config_word(pci_dev, PCI_COMMAND, cmd);
+
+    return ret;
+}

 /* find nvidia devices and set initial state */
 static int
@@ -428,6 +499,11 @@
         goto failed;
     }

+    if (!nv_resize_pcie_bars(pci_dev)) {
+        nv_printf(NV_DBG_ERRORS,
+            "NVRM: Fatal Error while attempting to resize PCIe BARs.\n");
+    }
+
     NV_KMALLOC(nvl, sizeof(nv_linux_state_t));
     if (nvl == NULL)
     {
@@ -470,6 +546,7 @@
     nvl->gpu_wakeup_callback_needed = NV_TRUE;
     INIT_LIST_HEAD(&nvl->open_files);

+
     for (i = 0, j = 0; i < NVRM_PCICFG_NUM_BARS && j < NV_GPU_NUM_BARS; i++)
     {
         if ((NV_PCI_RESOURCE_VALID(pci_dev, i)) &&