hw/pci-host: Fix x86 Host Bridges 64bit PCI hole

Currently there is no MMIO range over 4G
reserved for PCI hotplug. Since the 32bit PCI hole
depends on the number of cold-plugged PCI devices
and other factors, it is very possible is too small
to hotplug PCI devices with large BARs.

Fix it by reserving 2G for I4400FX chipset
in order to comply with older Win32 Guest OSes
and 32G for Q35 chipset.

Even if the new defaults of pci-hole64-size will appear in
"info qtree" also for older machines, the property was
not implemented so no changes will be visible to guests.

Note this is a regression since prev QEMU versions had
some range reserved for 64bit PCI hotplug.

Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Marcel Apfelbaum <marcel@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

1 files changed, 30 insertions, 2 deletions

diff --git a/hw/pci-host/piix.c b/hw/pci-host/piix.c
index a7e2256870..a684a7cca9 100644
--- a/hw/pci-host/piix.c
+++ b/hw/pci-host/piix.c
@@ -50,6 +50,7 @@ typedef struct I440FXState {
     PCIHostState parent_obj;
     Range pci_hole;
     uint64_t pci_hole64_size;
+    bool pci_hole64_fix;
     uint32_t short_root_bus;
 } I440FXState;
 
@@ -112,6 +113,9 @@ struct PCII440FXState {
 #define I440FX_PAM_SIZE 7
 #define I440FX_SMRAM    0x72
 
+/* Keep it 2G to comply with older win32 guests */
+#define I440FX_PCI_HOST_HOLE64_SIZE_DEFAULT (1ULL << 31)
+
 /* Older coreboot versions (4.0 and older) read a config register that doesn't
  * exist in real hardware, to get the RAM size from QEMU.
  */
@@ -238,29 +242,52 @@ static void i440fx_pcihost_get_pci_hole_end(Object *obj, Visitor *v,
     visit_type_uint32(v, name, &value, errp);
 }
 
+/*
+ * The 64bit PCI hole start is set by the Guest firmware
+ * as the address of the first 64bit PCI MEM resource.
+ * If no PCI device has resources on the 64bit area,
+ * the 64bit PCI hole will start after "over 4G RAM" and the
+ * reserved space for memory hotplug if any.
+ */
 static void i440fx_pcihost_get_pci_hole64_start(Object *obj, Visitor *v,
                                                 const char *name,
                                                 void *opaque, Error **errp)
 {
     PCIHostState *h = PCI_HOST_BRIDGE(obj);
+    I440FXState *s = I440FX_PCI_HOST_BRIDGE(obj);
     Range w64;
     uint64_t value;
 
     pci_bus_get_w64_range(h->bus, &w64);
     value = range_is_empty(&w64) ? 0 : range_lob(&w64);
+    if (!value && s->pci_hole64_fix) {
+        value = pc_pci_hole64_start();
+    }
     visit_type_uint64(v, name, &value, errp);
 }
 
+/*
+ * The 64bit PCI hole end is set by the Guest firmware
+ * as the address of the last 64bit PCI MEM resource.
+ * Then it is expanded to the PCI_HOST_PROP_PCI_HOLE64_SIZE
+ * that can be configured by the user.
+ */
 static void i440fx_pcihost_get_pci_hole64_end(Object *obj, Visitor *v,
                                               const char *name, void *opaque,
                                               Error **errp)
 {
     PCIHostState *h = PCI_HOST_BRIDGE(obj);
+    I440FXState *s = I440FX_PCI_HOST_BRIDGE(obj);
+    uint64_t hole64_start = pc_pci_hole64_start();
     Range w64;
-    uint64_t value;
+    uint64_t value, hole64_end;
 
     pci_bus_get_w64_range(h->bus, &w64);
     value = range_is_empty(&w64) ? 0 : range_upb(&w64) + 1;
+    hole64_end = ROUND_UP(hole64_start + s->pci_hole64_size, 1ULL << 30);
+    if (s->pci_hole64_fix && value < hole64_end) {
+        value = hole64_end;
+    }
     visit_type_uint64(v, name, &value, errp);
 }
 
@@ -863,8 +890,9 @@ static const char *i440fx_pcihost_root_bus_path(PCIHostState *host_bridge,
 
 static Property i440fx_props[] = {
     DEFINE_PROP_SIZE(PCI_HOST_PROP_PCI_HOLE64_SIZE, I440FXState,
-                     pci_hole64_size, DEFAULT_PCI_HOLE64_SIZE),
+                     pci_hole64_size, I440FX_PCI_HOST_HOLE64_SIZE_DEFAULT),
     DEFINE_PROP_UINT32("short_root_bus", I440FXState, short_root_bus, 0),
+    DEFINE_PROP_BOOL("x-pci-hole64-fix", I440FXState, pci_hole64_fix, true),
     DEFINE_PROP_END_OF_LIST(),
 };