vga-pci: add qext region to mmio

Add a qemu extented register range to the standard vga mmio bar.
Right nowe there are two registers:  One readonly register returning the
size of the region (so we can easily add more registers there if needed)
and one endian control register, so guests (especially ppc) can flip
the framebuffer endianness as they need it.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>

3 files changed, 87 insertions, 0 deletions

diff --git a/docs/specs/standard-vga.txt b/docs/specs/standard-vga.txt
index f82773e677..19d2a74509 100644
--- a/docs/specs/standard-vga.txt
+++ b/docs/specs/standard-vga.txt
@@ -70,3 +70,12 @@ Likewise applies to the pci variant only for obvious reasons.
 0500 - 0515 : bochs dispi interface registers, mapped flat
               without index/data ports.  Use (index << 1)
               as offset for (16bit) register access.
+
+0600 - 0607 : qemu extended registers.  qemu 2.2+ only.
+              The pci revision is 2 (or greater) when
+              these registers are present.  The registers
+              are 32bit.
+  0600      : qemu extended register region size, in bytes.
+  0604      : framebuffer endianness register.
+              - 0xbebebebe indicates big endian.
+              - 0x1e1e1e1e indicates little endian.
diff --git a/hw/display/vga-pci.c b/hw/display/vga-pci.c
index 0351d94707..db922f1843 100644
--- a/hw/display/vga-pci.c
+++ b/hw/display/vga-pci.c
@@ -35,10 +35,18 @@
 #define PCI_VGA_IOPORT_SIZE   (0x3e0 - 0x3c0)
 #define PCI_VGA_BOCHS_OFFSET  0x500
 #define PCI_VGA_BOCHS_SIZE    (0x0b * 2)
+#define PCI_VGA_QEXT_OFFSET   0x600
+#define PCI_VGA_QEXT_SIZE     (2 * 4)
 #define PCI_VGA_MMIO_SIZE     0x1000
 
+#define PCI_VGA_QEXT_REG_SIZE         (0 * 4)
+#define PCI_VGA_QEXT_REG_BYTEORDER    (1 * 4)
+#define  PCI_VGA_QEXT_LITTLE_ENDIAN   0x1e1e1e1e
+#define  PCI_VGA_QEXT_BIG_ENDIAN      0xbebebebe
+
 enum vga_pci_flags {
     PCI_VGA_FLAG_ENABLE_MMIO = 1,
+    PCI_VGA_FLAG_ENABLE_QEXT = 2,
 };
 
 typedef struct PCIVGAState {
@@ -48,6 +56,7 @@ typedef struct PCIVGAState {
     MemoryRegion mmio;
     MemoryRegion ioport;
     MemoryRegion bochs;
+    MemoryRegion qext;
 } PCIVGAState;
 
 static const VMStateDescription vmstate_vga_pci = {
@@ -140,6 +149,46 @@ static const MemoryRegionOps pci_vga_bochs_ops = {
     .endianness = DEVICE_LITTLE_ENDIAN,
 };
 
+static uint64_t pci_vga_qext_read(void *ptr, hwaddr addr, unsigned size)
+{
+    PCIVGAState *d = ptr;
+
+    switch (addr) {
+    case PCI_VGA_QEXT_REG_SIZE:
+        return PCI_VGA_QEXT_SIZE;
+    case PCI_VGA_QEXT_REG_BYTEORDER:
+        return d->vga.big_endian_fb ?
+            PCI_VGA_QEXT_BIG_ENDIAN : PCI_VGA_QEXT_LITTLE_ENDIAN;
+    default:
+        return 0;
+    }
+}
+
+static void pci_vga_qext_write(void *ptr, hwaddr addr,
+                               uint64_t val, unsigned size)
+{
+    PCIVGAState *d = ptr;
+
+    switch (addr) {
+    case PCI_VGA_QEXT_REG_BYTEORDER:
+        if (val == PCI_VGA_QEXT_BIG_ENDIAN) {
+            d->vga.big_endian_fb = true;
+        }
+        if (val == PCI_VGA_QEXT_LITTLE_ENDIAN) {
+            d->vga.big_endian_fb = false;
+        }
+        break;
+    }
+}
+
+static const MemoryRegionOps pci_vga_qext_ops = {
+    .read = pci_vga_qext_read,
+    .write = pci_vga_qext_write,
+    .valid.min_access_size = 4,
+    .valid.max_access_size = 4,
+    .endianness = DEVICE_LITTLE_ENDIAN,
+};
+
 static int pci_std_vga_initfn(PCIDevice *dev)
 {
     PCIVGAState *d = DO_UPCAST(PCIVGAState, dev, dev);
@@ -167,6 +216,15 @@ static int pci_std_vga_initfn(PCIDevice *dev)
                                     &d->ioport);
         memory_region_add_subregion(&d->mmio, PCI_VGA_BOCHS_OFFSET,
                                     &d->bochs);
+
+        if (d->flags & (1 << PCI_VGA_FLAG_ENABLE_QEXT)) {
+            memory_region_init_io(&d->qext, NULL, &pci_vga_qext_ops, d,
+                                  "qemu extended regs", PCI_VGA_QEXT_SIZE);
+            memory_region_add_subregion(&d->mmio, PCI_VGA_QEXT_OFFSET,
+                                        &d->qext);
+            pci_set_byte(&d->dev.config[PCI_REVISION_ID], 2);
+        }
+
         pci_register_bar(&d->dev, 2, PCI_BASE_ADDRESS_SPACE_MEMORY, &d->mmio);
     }
 
@@ -199,6 +257,14 @@ static int pci_secondary_vga_initfn(PCIDevice *dev)
     memory_region_add_subregion(&d->mmio, PCI_VGA_BOCHS_OFFSET,
                                 &d->bochs);
 
+    if (d->flags & (1 << PCI_VGA_FLAG_ENABLE_QEXT)) {
+        memory_region_init_io(&d->qext, NULL, &pci_vga_qext_ops, d,
+                              "qemu extended regs", PCI_VGA_QEXT_SIZE);
+        memory_region_add_subregion(&d->mmio, PCI_VGA_QEXT_OFFSET,
+                                    &d->qext);
+        pci_set_byte(&d->dev.config[PCI_REVISION_ID], 2);
+    }
+
     pci_register_bar(&d->dev, 0, PCI_BASE_ADDRESS_MEM_PREFETCH, &s->vram);
     pci_register_bar(&d->dev, 2, PCI_BASE_ADDRESS_SPACE_MEMORY, &d->mmio);
 
@@ -215,11 +281,15 @@ static void pci_secondary_vga_reset(DeviceState *dev)
 static Property vga_pci_properties[] = {
     DEFINE_PROP_UINT32("vgamem_mb", PCIVGAState, vga.vram_size_mb, 16),
     DEFINE_PROP_BIT("mmio", PCIVGAState, flags, PCI_VGA_FLAG_ENABLE_MMIO, true),
+    DEFINE_PROP_BIT("qemu-extended-regs",
+                    PCIVGAState, flags, PCI_VGA_FLAG_ENABLE_QEXT, true),
     DEFINE_PROP_END_OF_LIST(),
 };
 
 static Property secondary_pci_properties[] = {
     DEFINE_PROP_UINT32("vgamem_mb", PCIVGAState, vga.vram_size_mb, 16),
+    DEFINE_PROP_BIT("qemu-extended-regs",
+                    PCIVGAState, flags, PCI_VGA_FLAG_ENABLE_QEXT, true),
     DEFINE_PROP_END_OF_LIST(),
 };
 
diff --git a/include/hw/i386/pc.h b/include/hw/i386/pc.h
index 77316d55c8..1c2602efd7 100644
--- a/include/hw/i386/pc.h
+++ b/include/hw/i386/pc.h
@@ -306,6 +306,14 @@ bool e820_get_entry(int, uint32_t, uint64_t *, uint64_t *);
             .driver   = "intel-hda",\
             .property = "old_msi_addr",\
             .value    = "on",\
+        },{\
+            .driver   = "VGA",\
+            .property = "qemu-extended-regs",\
+            .value    = "off",\
+        },{\
+            .driver   = "secondary-vga",\
+            .property = "qemu-extended-regs",\
+            .value    = "off",\
         }
 
 #define PC_COMPAT_2_0 \