Revision 233677 broke certain machines. Specifically, if the firmware/BIOS

assigned conflicting ranges to BARs then leaving the BARs alone could
result in one device stealing mmio accesses intended to go to a second
device.  Prior to 233677 the PCI bus driver attempted to handle this case
by clearing the BAR to 0 depending on BARs based at 0 not decoding (which
is not guaranteed to be true).  Now when a conflicting BAR is detected the
following steps are taken:

 1) If hw.pci.realloc_bars (a new tunable) is enabled (default is enabled),
    then ignore the current BAR setting from the firmware and attempt to
    allocate a fresh resource range for the BAR.

 2) If 1) failed (or was disabled), disable decoding for the relevant
    BAR type (e.g. disable mem decoding for a memory BAR) and emit a
    warning if booting verbose.

Tested by:	Alex Keda <admin@lissyara.su>
MFC after:	1 week

1 files changed, 29 insertions, 2 deletions

diff --git a/sys/dev/pci/pci.c b/sys/dev/pci/pci.c
index 79d5e57..2851ab7 100644
--- a/sys/dev/pci/pci.c
+++ b/sys/dev/pci/pci.c
@@ -280,6 +280,12 @@ SYSCTL_INT(_hw_pci, OID_AUTO, enable_io_modes, CTLFLAG_RW,
 enable these bits correctly.  We'd like to do this all the time, but there\n\
 are some peripherals that this causes problems with.");
 
+static int pci_do_realloc_bars = 1;
+TUNABLE_INT("hw.pci.realloc_bars", &pci_do_realloc_bars);
+SYSCTL_INT(_hw_pci, OID_AUTO, realloc_bars, CTLFLAG_RW,
+    &pci_do_realloc_bars, 0,
+    "Attempt to allocate a new range for any BARs whose original firmware-assigned ranges fail to allocate during the initial device scan.");
+
 static int pci_do_power_nodriver = 0;
 TUNABLE_INT("hw.pci.do_power_nodriver", &pci_do_power_nodriver);
 SYSCTL_INT(_hw_pci, OID_AUTO, do_power_nodriver, CTLFLAG_RW,
@@ -2816,13 +2822,34 @@ pci_add_map(device_t bus, device_t dev, int reg, struct resource_list *rl,
 	 */
 	res = resource_list_reserve(rl, bus, dev, type, &reg, start, end, count,
 	    prefetch ? RF_PREFETCHABLE : 0);
+	if (pci_do_realloc_bars && res == NULL && (start != 0 || end != ~0ul)) {
+		/*
+		 * If the allocation fails, try to allocate a resource for
+		 * this BAR using any available range.  The firmware felt
+		 * it was important enough to assign a resource, so don't
+		 * disable decoding if we can help it.
+		 */
+		resource_list_delete(rl, type, reg);
+		resource_list_add(rl, type, reg, 0, ~0ul, count);
+		res = resource_list_reserve(rl, bus, dev, type, &reg, 0, ~0ul,
+		    count, prefetch ? RF_PREFETCHABLE : 0);
+	}
 	if (res == NULL) {
 		/*
 		 * If the allocation fails, delete the resource list entry
-		 * to force pci_alloc_resource() to allocate resources
-		 * from the parent.
+		 * and disable decoding for this device.
+		 *
+		 * If the driver requests this resource in the future,
+		 * pci_reserve_map() will try to allocate a fresh
+		 * resource range.
 		 */
 		resource_list_delete(rl, type, reg);
+		pci_disable_io(dev, type);
+		if (bootverbose)
+			device_printf(bus,
+			    "pci%d:%d:%d:%d bar %#x failed to allocate\n",
+			    pci_get_domain(dev), pci_get_bus(dev),
+			    pci_get_slot(dev), pci_get_function(dev), reg);
 	} else {
 		start = rman_get_start(res);
 		pci_write_bar(dev, pm, start);