@@ -2080,12 +2080,17 @@ static void prepopulate_bars(struct hv_pcibus_device *hbus)
}
}
if (high_size <= 1 && low_size <= 1) {
- /* Set the memory enable bit. */
- _hv_pcifront_read_config(hpdev, PCI_COMMAND, 2,
- &command);
- command |= PCI_COMMAND_MEMORY;
- _hv_pcifront_write_config(hpdev, PCI_COMMAND, 2,
- command);
+ /*
+ * No need to set the PCI_COMMAND_MEMORY bit as
+ * the core PCI driver doesn't require the bit
+ * to be pre-set. Actually here we intentionally
+ * keep the bit off so that the PCI BAR probing
+ * in the core PCI driver doesn't cause Hyper-V
+ * to unnecessarily unmap/map the virtual BARs
+ * from/to the physical BARs multiple times.
+ * This reduces the VM boot time significantly
+ * if the BAR sizes are huge.
+ */
break;
}
}