1 files changed, 18 insertions, 0 deletions

diff --git a/drivers/pci/setup-res.c b/drivers/pci/setup-res.c
index eea85dafc76..1a0e60e265e 100644
--- a/drivers/pci/setup-res.c
+++ b/drivers/pci/setup-res.c
@@ -30,6 +30,8 @@
 void pci_update_resource(struct pci_dev *dev, int resno)
 {
         struct pci_bus_region region;
+        bool disable;
+        u16 cmd;
         u32 new, check, mask;
         int reg;
         enum pci_bar_type type;
@@ -67,6 +69,18 @@ void pci_update_resource(struct pci_dev *dev, int resno)
                 new |= PCI_ROM_ADDRESS_ENABLE;
         }
 
+        /*
+         * We can't update a 64-bit BAR atomically, so when possible,
+         * disable decoding so that a half-updated BAR won't conflict
+         * with another device.
+         */
+        disable = (res->flags & IORESOURCE_MEM_64) && !dev->mmio_always_on;
+        if (disable) {
+                pci_read_config_word(dev, PCI_COMMAND, &cmd);
+                pci_write_config_word(dev, PCI_COMMAND,
+                                      cmd & ~PCI_COMMAND_MEMORY);
+        }
+
         pci_write_config_dword(dev, reg, new);
         pci_read_config_dword(dev, reg, &check);
 
@@ -84,6 +98,10 @@ void pci_update_resource(struct pci_dev *dev, int resno)
                                "(high %#08x != %#08x)\n", resno, new, check);
                 }
         }
+
+        if (disable)
+                pci_write_config_word(dev, PCI_COMMAND, cmd);
+
         res->flags &= ~IORESOURCE_UNSET;
         dev_dbg(&dev->dev, "BAR %d: set to %pR (PCI address [%#llx-%#llx])\n",
                 resno, res, (unsigned long long)region.start,