pseries: Limit PCI host bridge "index" value

pseries guests can have large numbers of PCI host bridges.  To avoid the
user having to specify a number of different configuration values for every
one, the device supports an "index" property which is a shorthand setting
the various window and configuration addresses from a predefined sensible
set.

There are some problems with the details at present:
  * The "index" propery is signed, but negative values will create PCI
windows below where we expect, potentially colliding with other devices
  * No limit is imposed on the "index" property and large values can
translate to extremely large window addresses.  With PCI passthrough in
particular this can mean we exceed various mapping and physical address
limits causing the guest host bridge to not work in strange ways.

This patch addresses this, by making "index" unsigned, and imposing a
limit.  Currently the limit allows indices from 0..255 which is probably
enough host bridges for the time being.  It's fairly easy to extend if
we discover we need more.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Michael Roth <mdroth@linux.vnet.ibm.com>
Signed-off-by: Alexander Graf <agraf@suse.de>

2 files changed, 10 insertions, 2 deletions

diff --git a/hw/ppc/spapr_pci.c b/hw/ppc/spapr_pci.c
index 21b95b3..6deeb19 100644
--- a/hw/ppc/spapr_pci.c
+++ b/hw/ppc/spapr_pci.c
@@ -501,6 +501,12 @@ static void spapr_phb_realize(DeviceState *dev, Error **errp)
             return;
         }
 
+        if (sphb->index > SPAPR_PCI_MAX_INDEX) {
+            error_setg(errp, "\"index\" for PAPR PHB is too large (max %u)",
+                       SPAPR_PCI_MAX_INDEX);
+            return;
+        }
+
         sphb->buid = SPAPR_PCI_BASE_BUID + sphb->index;
         sphb->dma_liobn = SPAPR_PCI_BASE_LIOBN + sphb->index;
 
@@ -669,7 +675,7 @@ static void spapr_phb_reset(DeviceState *qdev)
 }
 
 static Property spapr_phb_properties[] = {
-    DEFINE_PROP_INT32("index", sPAPRPHBState, index, -1),
+    DEFINE_PROP_UINT32("index", sPAPRPHBState, index, -1),
     DEFINE_PROP_UINT64("buid", sPAPRPHBState, buid, -1),
     DEFINE_PROP_UINT32("liobn", sPAPRPHBState, dma_liobn, -1),
     DEFINE_PROP_UINT64("mem_win_addr", sPAPRPHBState, mem_win_addr, -1),
diff --git a/include/hw/pci-host/spapr.h b/include/hw/pci-host/spapr.h
index 4ea2a0d..876ecf0 100644
--- a/include/hw/pci-host/spapr.h
+++ b/include/hw/pci-host/spapr.h
@@ -64,7 +64,7 @@ typedef struct spapr_pci_msi_mig {
 struct sPAPRPHBState {
     PCIHostState parent_obj;
 
-    int32_t index;
+    uint32_t index;
     uint64_t buid;
     char *dtbusname;
 
@@ -94,6 +94,8 @@ struct sPAPRPHBVFIOState {
     int32_t iommugroupid;
 };
 
+#define SPAPR_PCI_MAX_INDEX          255
+
 #define SPAPR_PCI_BASE_BUID          0x800000020000000ULL
 
 #define SPAPR_PCI_WINDOW_BASE        0x10000000000ULL