[Qemu-devel] [PATCH v2] pci: Teach PCI Bridges about VGA routing

[Alex Williamson]

Each PCI Bridge has a set of implied VGA regions that are enabled
when the VGA bit is set in the bridge control register.  This allows
VGA devices behind bridges.

Signed-off-by: Alex Williamson <address@hidden>
---

v2: BRIDGE_CONTROL is 2 bytes

 hw/pci/pci_bridge.c |   45 +++++++++++++++++++++++++++++++++++++++++++--
 hw/pci/pci_bus.h    |   15 +++++++++++++++
 2 files changed, 58 insertions(+), 2 deletions(-)

diff --git a/hw/pci/pci_bridge.c b/hw/pci/pci_bridge.c
index 995842a..ced0e95 100644
--- a/hw/pci/pci_bridge.c
+++ b/hw/pci/pci_bridge.c
@@ -151,6 +151,37 @@ static void pci_bridge_init_alias(PCIBridge *bridge, 
MemoryRegion *alias,
     memory_region_add_subregion_overlap(parent_space, base, alias, 1);
 }
 
+static void pci_bridge_init_vga_aliases(PCIBridge *br, PCIBus *parent,
+                                        PCIBridgeVgaWindows *vga)
+{
+    uint16_t cmd = pci_get_word(br->dev.config + PCI_COMMAND);
+    uint16_t brctl = pci_get_word(br->dev.config + PCI_BRIDGE_CONTROL);
+
+    memory_region_init_alias(&vga->alias_io_lo, "pci_bridge_vga_io_lo",
+                             &br->address_space_io, 0x3b0, 0xc);
+    memory_region_add_subregion_overlap(parent->address_space_io, 0x3b0,
+                                        &vga->alias_io_lo, 1);
+
+    memory_region_init_alias(&vga->alias_io_hi, "pci_bridge_vga_io_hi",
+                             &br->address_space_io, 0x3c0, 0x20);
+    memory_region_add_subregion_overlap(parent->address_space_io, 0x3c0,
+                                        &vga->alias_io_hi, 1);
+
+    if (!(cmd & PCI_COMMAND_IO) || !(brctl & PCI_BRIDGE_CTL_VGA)) {
+        memory_region_set_enabled(&vga->alias_io_lo, false);
+        memory_region_set_enabled(&vga->alias_io_hi, false);
+    }
+
+    memory_region_init_alias(&vga->alias_mem, "pci_bridge_vga_mem",
+                             &br->address_space_mem, 0xa0000, 0x20000);
+    memory_region_add_subregion_overlap(parent->address_space_mem, 0xa0000,
+                                        &vga->alias_mem, 1);
+
+    if (!(cmd & PCI_COMMAND_MEMORY) || !(brctl & PCI_BRIDGE_CTL_VGA)) {
+        memory_region_set_enabled(&vga->alias_mem, false);
+    }
+}
+
 static PCIBridgeWindows *pci_bridge_region_init(PCIBridge *br)
 {
     PCIBus *parent = br->dev.bus;
@@ -175,7 +206,8 @@ static PCIBridgeWindows *pci_bridge_region_init(PCIBridge 
*br)
                           &br->address_space_io,
                           parent->address_space_io,
                           cmd & PCI_COMMAND_IO);
-   /* TODO: optinal VGA and VGA palette snooping support. */
+
+    pci_bridge_init_vga_aliases(br, parent, &w->vga);
 
     return w;
 }
@@ -187,6 +219,9 @@ static void pci_bridge_region_del(PCIBridge *br, 
PCIBridgeWindows *w)
     memory_region_del_subregion(parent->address_space_io, &w->alias_io);
     memory_region_del_subregion(parent->address_space_mem, &w->alias_mem);
     memory_region_del_subregion(parent->address_space_mem, &w->alias_pref_mem);
+    memory_region_del_subregion(parent->address_space_io, &w->vga.alias_io_lo);
+    memory_region_del_subregion(parent->address_space_io, &w->vga.alias_io_hi);
+    memory_region_del_subregion(parent->address_space_mem, &w->vga.alias_mem);
 }
 
 static void pci_bridge_region_cleanup(PCIBridge *br, PCIBridgeWindows *w)
@@ -194,6 +229,9 @@ static void pci_bridge_region_cleanup(PCIBridge *br, 
PCIBridgeWindows *w)
     memory_region_destroy(&w->alias_io);
     memory_region_destroy(&w->alias_mem);
     memory_region_destroy(&w->alias_pref_mem);
+    memory_region_destroy(&w->vga.alias_io_lo);
+    memory_region_destroy(&w->vga.alias_io_hi);
+    memory_region_destroy(&w->vga.alias_mem);
     g_free(w);
 }
 
@@ -227,7 +265,10 @@ void pci_bridge_write_config(PCIDevice *d,
 
         /* memory base/limit, prefetchable base/limit and
            io base/limit upper 16 */
-        ranges_overlap(address, len, PCI_MEMORY_BASE, 20)) {
+        ranges_overlap(address, len, PCI_MEMORY_BASE, 20) ||
+
+        /* vga enable */
+        ranges_overlap(address, len, PCI_BRIDGE_CONTROL, 2)) {
         pci_bridge_update_mappings(s);
     }
 
diff --git a/hw/pci/pci_bus.h b/hw/pci/pci_bus.h
index f905b9e..60d5378 100644
--- a/hw/pci/pci_bus.h
+++ b/hw/pci/pci_bus.h
@@ -36,6 +36,20 @@ struct PCIBus {
     int *irq_count;
 };
 
+typedef struct PCIBridgeVgaWindows PCIBridgeVgaWindows;
+
+/*
+ * When bridge control VGA forwarding is enabled, bridges will provide
+ * positive decode on the PCI VGA defined I/O port and MMIO ranges noted
+ * below.  When set, forwarding is only qualified on the I/O and memory
+ * enable bits in the bridge command register.
+ */
+struct PCIBridgeVgaWindows {
+    MemoryRegion alias_io_lo; /* I/O ports 0x3b0 - 0x3bb */
+    MemoryRegion alias_io_hi; /* I/O ports 0x3c0 - 0x3df */
+    MemoryRegion alias_mem; /* MMIO 0xa0000 - 0xbffff */
+};
+
 typedef struct PCIBridgeWindows PCIBridgeWindows;
 
 /*
@@ -47,6 +61,7 @@ struct PCIBridgeWindows {
     MemoryRegion alias_pref_mem;
     MemoryRegion alias_mem;
     MemoryRegion alias_io;
+    PCIBridgeVgaWindows vga;
 };
 
 struct PCIBridge {