[PATCH v2 1/2] hw/i386/postcard.c: New ISA POST card device

[Lev Kujawski]

Relocate the ioport80 functionality within hw/i386/pc.c into a new ISA
POST card device (postcard.c) that is capable of being instantiated at
different ports as well, such as for the following platforms [1]:
  0x84  for COMPAQ
  0x90  for PS/2 (ISA)
  0x300 for AWARD BIOS
  0x680 for PS/2 (MCA)

Emulate i440FX hardware by storing the value written to the port, a
behavior relied upon by firmware for these systems (e.g., AMIBIOS) to
track the state of the boot process.  Despite the name of this device,
said behavior does not rely upon the presence of an installed POST
card, as the chipset provides an extraneous DMA page register at the
POST address.

To aid firmware debugging, allow for tracing POST card values,
mimicking the [new value, old value] display format of physical cards.

Reference platform:
  TYAN S1686D (i440FX system board)

References:
  [1] F. v. Gilluwe, The Undocumented PC. Boston, MA: Addison-Wesley,
      1997, p. 800-801.

Signed-off-by: Lev Kujawski <lkujaw@member.fsf.org>
---
 (v2) No functional changes. Add myself as the maintainer of this device,
      per checkpatch; add technical details and references to commit log.

 MAINTAINERS                |   5 ++
 hw/i386/Kconfig            |   5 ++
 hw/i386/meson.build        |   1 +
 hw/i386/pc.c               |  25 +------
 hw/i386/postcard.c         | 149 +++++++++++++++++++++++++++++++++++++
 hw/i386/trace-events       |   3 +
 include/hw/i386/postcard.h |  35 +++++++++
 7 files changed, 200 insertions(+), 23 deletions(-)
 create mode 100644 hw/i386/postcard.c
 create mode 100644 include/hw/i386/postcard.h

diff --git a/MAINTAINERS b/MAINTAINERS
index 450abd0252..33b13583b7 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -1719,6 +1719,11 @@ F: include/sysemu/numa.h
 F: tests/unit/test-smp-parse.c
 T: git https://gitlab.com/ehabkost/qemu.git machine-next
 
+ISA POST card
+M: Lev Kujawski <lkujaw@member.fsf.org>
+S: Supported
+F: hw/i386/postcard.c
+
 Xtensa Machines
 ---------------
 sim
diff --git a/hw/i386/Kconfig b/hw/i386/Kconfig
index d22ac4a4b9..17979e5c0d 100644
--- a/hw/i386/Kconfig
+++ b/hw/i386/Kconfig
@@ -10,6 +10,10 @@ config SGX
     bool
     depends on KVM
 
+config POST_CARD
+    bool
+    depends on ISA_BUS
+
 config PC
     bool
     imply APPLESMC
@@ -40,6 +44,7 @@ config PC
     select PCSPK
     select I8257
     select MC146818RTC
+    select POST_CARD
     # For ACPI builder:
     select SERIAL_ISA
     select ACPI_PCI
diff --git a/hw/i386/meson.build b/hw/i386/meson.build
index 213e2e82b3..c883e8ec9a 100644
--- a/hw/i386/meson.build
+++ b/hw/i386/meson.build
@@ -28,6 +28,7 @@ i386_ss.add(when: 'CONFIG_PC', if_true: files(
   'port92.c'))
 i386_ss.add(when: 'CONFIG_X86_FW_OVMF', if_true: files('pc_sysfw_ovmf.c'),
                                         if_false: 
files('pc_sysfw_ovmf-stubs.c'))
+i386_ss.add(when: 'CONFIG_POST_CARD', if_true: files('postcard.c'))
 
 subdir('kvm')
 subdir('xen')
diff --git a/hw/i386/pc.c b/hw/i386/pc.c
index 774cb2bf07..c179e38a61 100644
--- a/hw/i386/pc.c
+++ b/hw/i386/pc.c
@@ -32,6 +32,7 @@
 #include "hw/i386/topology.h"
 #include "hw/i386/fw_cfg.h"
 #include "hw/i386/vmport.h"
+#include "hw/i386/postcard.h"
 #include "sysemu/cpus.h"
 #include "hw/block/fdc.h"
 #include "hw/ide.h"
@@ -403,16 +404,6 @@ GSIState *pc_gsi_create(qemu_irq **irqs, bool pci_enabled)
     return s;
 }
 
-static void ioport80_write(void *opaque, hwaddr addr, uint64_t data,
-                           unsigned size)
-{
-}
-
-static uint64_t ioport80_read(void *opaque, hwaddr addr, unsigned size)
-{
-    return 0xffffffffffffffffULL;
-}
-
 /* MSDOS compatibility mode FPU exception support */
 static void ioportF0_write(void *opaque, hwaddr addr, uint64_t data,
                            unsigned size)
@@ -1059,16 +1050,6 @@ DeviceState *pc_vga_init(ISABus *isa_bus, PCIBus 
*pci_bus)
     return dev;
 }
 
-static const MemoryRegionOps ioport80_io_ops = {
-    .write = ioport80_write,
-    .read = ioport80_read,
-    .endianness = DEVICE_NATIVE_ENDIAN,
-    .impl = {
-        .min_access_size = 1,
-        .max_access_size = 1,
-    },
-};
-
 static const MemoryRegionOps ioportF0_io_ops = {
     .write = ioportF0_write,
     .read = ioportF0_read,
@@ -1139,12 +1120,10 @@ void pc_basic_device_init(struct PCMachineState *pcms,
     qemu_irq pit_alt_irq = NULL;
     qemu_irq rtc_irq = NULL;
     ISADevice *pit = NULL;
-    MemoryRegion *ioport80_io = g_new(MemoryRegion, 1);
     MemoryRegion *ioportF0_io = g_new(MemoryRegion, 1);
     X86MachineState *x86ms = X86_MACHINE(pcms);
 
-    memory_region_init_io(ioport80_io, NULL, &ioport80_io_ops, NULL, 
"ioport80", 1);
-    memory_region_add_subregion(isa_bus->address_space_io, 0x80, ioport80_io);
+    (void)post_card_init(isa_bus, POST_CARD_PORT_DEFAULT);
 
     memory_region_init_io(ioportF0_io, NULL, &ioportF0_io_ops, NULL, 
"ioportF0", 1);
     memory_region_add_subregion(isa_bus->address_space_io, 0xf0, ioportF0_io);
diff --git a/hw/i386/postcard.c b/hw/i386/postcard.c
new file mode 100644
index 0000000000..c9fa263510
--- /dev/null
+++ b/hw/i386/postcard.c
@@ -0,0 +1,149 @@
+/*
+ * QEMU PC System Emulator
+ *
+ * Copyright (c) 2003-2004 Fabrice Bellard
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to 
deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING 
FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#include "qemu/osdep.h"
+#include "exec/memory.h"
+#include "qapi/error.h"
+#include "qom/object.h"
+#include "migration/vmstate.h"
+#include "hw/qdev-properties.h"
+#include "trace.h"
+#include "hw/i386/postcard.h"
+
+struct POSTCardState {
+    ISADevice parent_obj;
+
+    MemoryRegion io;
+    uint16_t port;
+    uint8_t mem;
+};
+
+#define TYPE_POST_CARD "post-card"
+OBJECT_DECLARE_SIMPLE_TYPE(POSTCardState, POST_CARD)
+
+static uint64_t
+post_card_read(void *opaque, hwaddr addr, unsigned size)
+{
+    POSTCardState *s = opaque;
+    uint64_t val;
+
+    memset(&val, s->mem, sizeof(val));
+    return val;
+}
+
+static void
+post_card_write(void *opaque, hwaddr addr, uint64_t data, unsigned size)
+{
+    POSTCardState *s = opaque;
+    const uint8_t val = data & 0xff;
+
+    if (val != s->mem) {
+        trace_post_card_write(val, s->mem);
+        s->mem = val;
+    }
+}
+
+static const MemoryRegionOps post_card_ops = {
+    .read = post_card_read,
+    .write = post_card_write,
+    .endianness = DEVICE_NATIVE_ENDIAN,
+};
+
+static void
+post_card_reset(DeviceState *dev)
+{
+    POSTCardState *s = POST_CARD(dev);
+    s->mem = 0;
+}
+
+static void
+post_card_realize(DeviceState *dev, Error **errp)
+{
+    ISADevice *isadev = ISA_DEVICE(dev);
+    POSTCardState *s = POST_CARD(dev);
+
+    memory_region_init_io(&s->io, OBJECT(s), &post_card_ops,
+                          s, TYPE_POST_CARD, 1);
+    isa_register_ioport(isadev, &s->io, s->port);
+    post_card_reset(dev);
+}
+
+static Property post_card_properties[] = {
+    DEFINE_PROP_UINT16("iobase", POSTCardState, port,
+                       POST_CARD_PORT_DEFAULT),
+    DEFINE_PROP_END_OF_LIST(),
+};
+
+static const VMStateDescription post_card_vmstate = {
+    .name = TYPE_POST_CARD,
+    .version_id = 1,
+    .minimum_version_id = 1,
+    .fields = (VMStateField[]) {
+        VMSTATE_UINT16(port, POSTCardState),
+        VMSTATE_UINT8(mem, POSTCardState),
+        VMSTATE_END_OF_LIST()
+    }
+};
+
+static void
+post_card_class_init(ObjectClass *oc, void *data)
+{
+    DeviceClass *dc = DEVICE_CLASS(oc);
+
+    dc->desc = "ISA POST card";
+    dc->realize = post_card_realize;
+    dc->reset = post_card_reset;
+    dc->vmsd = &post_card_vmstate;
+    device_class_set_props(dc, post_card_properties);
+    set_bit(DEVICE_CATEGORY_MISC, dc->categories);
+}
+
+static const TypeInfo post_card_info = {
+    .name          = TYPE_POST_CARD,
+    .parent        = TYPE_ISA_DEVICE,
+    .instance_size = sizeof(POSTCardState),
+    .class_init    = post_card_class_init,
+};
+
+ISADevice *
+post_card_init(ISABus *bus, uint16_t iobase)
+{
+    DeviceState *dev;
+    ISADevice *isadev;
+
+    isadev = isa_new(TYPE_POST_CARD);
+    dev = DEVICE(isadev);
+    qdev_prop_set_uint16(dev, "iobase", iobase);
+    isa_realize_and_unref(isadev, bus, &error_fatal);
+
+    return isadev;
+}
+
+static void
+post_card_register_types(void)
+{
+    type_register_static(&post_card_info);
+}
+
+type_init(post_card_register_types)
diff --git a/hw/i386/trace-events b/hw/i386/trace-events
index e49814dd64..443c2a9d6a 100644
--- a/hw/i386/trace-events
+++ b/hw/i386/trace-events
@@ -119,3 +119,6 @@ x86_pic_interrupt(int irqn, int level) "PIC interrupt #%d 
level:%d"
 # port92.c
 port92_read(uint8_t val) "port92: read 0x%02x"
 port92_write(uint8_t val) "port92: write 0x%02x"
+
+# postcard.c
+post_card_write(uint8_t new_val, uint8_t old_val) "[%.2x %.2x]"
diff --git a/include/hw/i386/postcard.h b/include/hw/i386/postcard.h
new file mode 100644
index 0000000000..ae8cdb704a
--- /dev/null
+++ b/include/hw/i386/postcard.h
@@ -0,0 +1,35 @@
+/*
+ * QEMU PC System Emulator
+ *
+ * Copyright (c) 2003-2004 Fabrice Bellard
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to 
deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING 
FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#ifndef HW_I386_POSTCARD_H
+#define HW_I386_POSTCARD_H
+
+#include "hw/isa/isa.h"
+
+#define POST_CARD_PORT_DEFAULT 0x80
+
+ISADevice *
+post_card_init(ISABus *bus, uint16_t iobase);
+
+#endif /* HW_I386_POSTCARD_H */
-- 
2.34.1