x86/PCI: Add "pci=big_root_window" option for AMD 64-bit windows

[linux.git] / Documentation / admin-guide / kernel-parameters.txt

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 6571fbfdb2a1527c25b3a01e9c4228c84adce639..6196383624165985ba3ec45961b7acc63d99313c 100644 (file)
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -3094,6 +3094,12 @@
                pcie_scan_all   Scan all possible PCIe devices.  Otherwise we
                                only look for one device below a PCIe downstream
                                port.
+               big_root_window Try to add a big 64bit memory window to the PCIe
+                               root complex on AMD CPUs. Some GFX hardware
+                               can resize a BAR to allow access to all VRAM.
+                               Adding the window is slightly risky (it may
+                               conflict with unreported devices), so this
+                               taints the kernel.
 
        pcie_aspm=      [PCIE] Forcibly enable or disable PCIe Active State Power
                        Management.