x86/PCI: Move and shrink AMD 64-bit window to avoid conflict

Avoid problems with BIOS implementations which don't report all used
resources to the OS by only allocating a 256GB window directly below the
hardware limit (from the BKDG, sec 2.4.6).

Fixes a silent reboot loop reported by Aaro Koskinen <aaro.koskinen@iki.fi>
on an AMD-based MSI MS-7699/760GA-P43(FX) system.  This was apparently
caused by RAM or other unreported hardware that conflicted with the new
window.

Link: https://support.amd.com/TechDocs/49125_15h_Models_30h-3Fh_BKDG.pdf
Link: https://lkml.kernel.org/r/20180105220412.fzpwqe4zljdawr36@darkstar.musicnaut.iki.fi
Fixes: fa564ad96366 ("x86/PCI: Enable a 64bit BAR on AMD Family 15h (Models 00-1f, 30-3f, 60-7f)")
Reported-by: Aaro Koskinen <aaro.koskinen@iki.fi>
Signed-off-by: Christian König <christian.koenig@amd.com>
[bhelgaas: changelog, comment, Fixes:]
Signed-off-by: Bjorn Helgaas <helgaas@kernel.org>

1 files changed, 12 insertions, 10 deletions

diff --git a/arch/x86/pci/fixup.c b/arch/x86/pci/fixup.c
index 8bad19c7473d..f6a26e3cb476 100644
--- a/arch/x86/pci/fixup.c
+++ b/arch/x86/pci/fixup.c
@@ -662,10 +662,11 @@ DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_INTEL, 0x2033, quirk_no_aersid);
  */
 static void pci_amd_enable_64bit_bar(struct pci_dev *dev)
 {
-        unsigned i;
         u32 base, limit, high;
-        struct resource *res, *conflict;
         struct pci_dev *other;
+        struct resource *res;
+        unsigned i;
+        int r;
 
         if (!(pci_probe & PCI_BIG_ROOT_WINDOW))
                 return;
@@ -702,19 +703,20 @@ static void pci_amd_enable_64bit_bar(struct pci_dev *dev)
         if (!res)
                 return;
 
+        /*
+         * Allocate a 256GB window directly below the 0xfd00000000 hardware
+         * limit (see AMD Family 15h Models 30h-3Fh BKDG, sec 2.4.6).
+         */
         res->name = "PCI Bus 0000:00";
         res->flags = IORESOURCE_PREFETCH | IORESOURCE_MEM |
                 IORESOURCE_MEM_64 | IORESOURCE_WINDOW;
-        res->start = 0x100000000ull;
+        res->start = 0xbd00000000ull;
         res->end = 0xfd00000000ull - 1;
 
-        /* Just grab the free area behind system memory for this */
-        while ((conflict = request_resource_conflict(&iomem_resource, res))) {
-                if (conflict->end >= res->end) {
-                        kfree(res);
-                        return;
-                }
-                res->start = conflict->end + 1;
+        r = request_resource(&iomem_resource, res);
+        if (r) {
+                kfree(res);
+                return;
         }
 
         dev_info(&dev->dev, "adding root bus resource %pR (tainting kernel)\n",