[虚拟化/云][全栈demo] 为qemu增加一个PCI的watchdog外设（二）

这篇文章的理解，需要一些专业知识了。

我们可以创建模拟自己的外设吗？

我们已经知道什么是qemu了，我们可以通过qmeu的提供的外设，DIY一个计算机了。

但是我们可能还不满足，我们可以自己制造一个外设吗？

答案是可以的。而且这是了解计算机体系结构的一个很好的实践活动。

watchdog 外设

watchdog, 即看门狗。 如果狗饿了，便会”咬人“（CPU），让CPU重新启动。 为了不让狗狗”咬人“，我们需要不停的喂他。

我们将创建一个最简单的PCI的外设watchdog。如果你是一个硬件工程师或集成电路工程师，那么你肯定知道watchdog是什么东西， 并且可以很轻松的自行设计一个watchdog了。

但是我们这里创建的watchdog，是基于qemu架构的软件模拟的设备。

预备知识：

1. git 基本操作。

2. C 语言。

3. PCI的一些知识。

4. 阅读qemu 的文档 http://wiki.qemu.org/Manual

开发平台：

linux

实践：

1. clone一个qemu的仓库 http://wiki.qemu.org/Download

$ git clone git://git.qemu.org/qemu.git

2. 切换到一个新分支,一定从5d92c74 检出（checkout）

$ git checkout -b watchdog 5d92c74

3. 写源代码。

将下面的代码watchdog_source.patch（见代码目录）保存到本地， 注意去掉代码前面的行好。 现在不分析代码。以后会分析。这个代码已经测试过是可以运行的。

然后应用到qemu中。

$ git apply watchdog_source.patch

4. 配置qemu  http://wiki.qemu.org/Documentation/9psetup

$ ./configure '--target-list=x86_64-softmmu' '--enable-debug' '--enable-kvm' '--enable-spice' '--prefix=/home/shhfeng/qemu/'

4. 编译源代码。 http://wiki.qemu.org/Hosts/Linux

$ make

5. 测试代码 http://wiki.qemu.org/Documentation/QemuIoTests

将下面的代码watchdog_testcase.patch（见代码目录）保存到本地， 注意去掉代码前面的行好。 现在不分析代码。以后会分析。这个代码已经测试过是可以运行的。

然后应用到qemu中。

$ git apply watchdog_testcase.patch

$ make check-qtest-x86_64

6. 启动qemu with cstl-watchdog

$ x86_64-softmmu/qemu-system-x86_64 -device cstl-watchdog

注意：这里不能使用: $ x86_64-softmmu/qemu-system-x86_64 -watchdog cstl-watchdog

是因为没有在cstl-watchdog.c 中定义： WatchdogTimerModel

此外watchdog没有支持中断， 请参考 http://www.cnblogs.com/lihuidashen/p/4462220.html

代码目录：

1. watchdog_source.patch

 diff --git a/hw/watchdog/Makefile.objs b/hw/watchdog/Makefile.objs
 index 4b0374a..8f34e78
 --- a/hw/watchdog/Makefile.objs
 +++ b/hw/watchdog/Makefile.objs
 @@ -, +, @@
 -common-obj-y += watchdog.o
 +common-obj-y += watchdog.o cstl-watchdog.o
  common-obj-$(CONFIG_WDT_IB6300ESB) += wdt_i6300esb.o
  common-obj-$(CONFIG_WDT_IB700) += wdt_ib700.o
 diff --git a/hw/watchdog/cstl-watchdog.c b/hw/watchdog/cstl-watchdog.c
 new file mode
 index ..3ce043a
 --- /dev/null
 +++ b/hw/watchdog/cstl-watchdog.c
 @@ -, +, @@
 +/*
 + * Watch Dog Timer Demo
 + *
 + * This work is licensed under the terms of the GNU GPL, version 2 or later.
 + * See the COPYING file in the top-level directory.
 + *
 + */
 +
 +#include "qemu/timer.h"
 +#include "hw/hw.h"
 +#include "hw/pci/pci.h"
 +#include "sysemu/sysemu.h"
 +
 +typedef struct CSTLWatchdogState {
 +    PCIDevice dev;
 +
 +    uint8_t activated;
 +
 +    uint8_t triggered;
 +
 +    uint32_t missed_ticks;
 +
 +    QEMUTimer *watchdog_timer;
 +
 +    uint32_t expiration_ticks;
 +
 +    MemoryRegion io;
 +} CSTLWatchdogState;
 +#define TYPE_CSTL_WATCHDOG "cstl-watchdog"
 +#define CSTL_WATCHDOG(obj) \
 +    OBJECT_CHECK(CSTLWatchdogState, (obj), TYPE_CSTL_WATCHDOG)
 +
 +static void cwd_timer_event(void *opaque)
 +{
 +    CSTLWatchdogState *s = CSTL_WATCHDOG(opaque);
 +
 +    (void)s;
 +
 +    printf("watch dog fire!\n");
 +    if (!s->triggered) {
 +        s->missed_ticks++;
 +    }
 +
 +    s->triggered = ;
 +
 +    if (s->missed_ticks > ) {
 +        printf("WARNING: missed watchdog tick\n");
 +    }
 +
 +    if (s->missed_ticks > s->expiration_ticks) {
 +        printf("Watchdog expired!\n");
 +        qemu_system_reset_request();
 +    }
 +
 +
 +    if (s->activated) {
 +        timer_mod(s->watchdog_timer,
 +                  qemu_clock_get_ms(QEMU_CLOCK_REALTIME) + );
 +    }
 +}
 +
 +static uint64_t cwd_io_read(void *opaque, hwaddr addr,
 +                            unsigned size)
 +{
 +    CSTLWatchdogState *s = CSTL_WATCHDOG(opaque);
 +
 +    switch (addr) {
 +    case 0x00:
 +        return 0x42;
 +    case 0x01:
 +        return s->activated;
 +    default:
 +        break;
 +    }
 +
 +    return ;
 +}
 +
 +static void cwd_io_write(void *opaque, hwaddr addr,
 +                         uint64_t val, unsigned size)
 +{
 +    CSTLWatchdogState *s = CSTL_WATCHDOG(opaque);
 +
 +    switch (addr) {
 +    case 0x00:
 +        /* read-only */
 +        break;
 +    case 0x01:
 +        s->activated = !!val;
 +
 +        if (s->activated) {
 +            printf("Activated!\n");
 +            cwd_timer_event(s);
 +        } else {
 +            printf("Deactivated!\n");
 +            timer_del(s->watchdog_timer);
 +        }
 +        break;
 +    case 0x02:
 +        s->triggered = ;
 +        s->missed_ticks = ;
 +        break;
 +    default:
 +        break;
 +    }
 +}
 +
 +static const MemoryRegionOps cwd_io_ops = {
 +    .read = cwd_io_read,
 +    .write = cwd_io_write,
 +    .endianness = DEVICE_LITTLE_ENDIAN,
 +};
 +
 +static const VMStateDescription vmstate_cwd = {
 +    .name = TYPE_CSTL_WATCHDOG,
 +    .version_id = ,
 +    .fields      = (VMStateField []) {
 +        VMSTATE_PCI_DEVICE(dev, CSTLWatchdogState),
 +        VMSTATE_UINT8(activated, CSTLWatchdogState),
 +        VMSTATE_TIMER(watchdog_timer, CSTLWatchdogState),
 +        VMSTATE_UINT8(triggered, CSTLWatchdogState),
 +        VMSTATE_UINT32(missed_ticks, CSTLWatchdogState),
 +        VMSTATE_END_OF_LIST()
 +    }
 +};
 +
 +static void cwd_unrealize(PCIDevice *dev)
 +{
 +}
 +
 +static int cwd_realize(PCIDevice *pci_dev)
 +{
 +    CSTLWatchdogState *s = CSTL_WATCHDOG(pci_dev);
 +
 +    pci_register_bar(pci_dev, , PCI_BASE_ADDRESS_SPACE_IO, &s->io);
 +
 +    return ;
 +}
 +
 +static void cwd_reset(DeviceState *dev)
 +{
 +    CSTLWatchdogState *s = CSTL_WATCHDOG(dev);
 +
 +    s->activated = ;
 +    s->triggered = ;
 +    s->missed_ticks = ;
 +}
 +
 +static void cwd_initfn(Object *obj)
 +{
 +    CSTLWatchdogState *s = CSTL_WATCHDOG(obj);
 +
 +    memory_region_init_io(&s->io, OBJECT(s), &cwd_io_ops, s, "cstl-watchdog-io", );
 +
 +    s->watchdog_timer = timer_new_ms(QEMU_CLOCK_REALTIME, cwd_timer_event, s);
 +}
 +
 +static Property cwd_properties[] = {
 +    DEFINE_PROP_UINT32("expiration-ticks", CSTLWatchdogState,
 +                       expiration_ticks, ),
 +    DEFINE_PROP_END_OF_LIST(),
 +};
 +
 +static void cwd_class_init(ObjectClass *klass, void *data)
 +{
 +    DeviceClass *dc = DEVICE_CLASS(klass);
 +    PCIDeviceClass *k = PCI_DEVICE_CLASS(klass);
 +
 +    k->init = cwd_realize;
 +    k->exit = cwd_unrealize;
 +    k->vendor_id = PCI_VENDOR_ID_REDHAT_QUMRANET;
 +    k->device_id = 0x0101;
 +    k->revision = 0x01;
 +    k->class_id = PCI_CLASS_SYSTEM_OTHER;
 +    dc->reset = cwd_reset;
 +    dc->vmsd = &vmstate_cwd;
 +    dc->props = cwd_properties;
 +}
 +
 +static TypeInfo cstl_watchdog_info = {
 +    .name          = TYPE_CSTL_WATCHDOG,
 +    .parent        = TYPE_PCI_DEVICE,
 +    .instance_init = cwd_initfn,
 +    .instance_size = sizeof(CSTLWatchdogState),
 +    .class_init    = cwd_class_init,
 +};
 +
 +static void register_types(void)
 +{
 +    type_register_static(&cstl_watchdog_info);
 +}
 +
 +type_init(register_types)

2. watchdog_testcase.patch

 diff --git a/tests/Makefile b/tests/Makefile
 index 471b4c8..0a8f2cd
 --- a/tests/Makefile
 +++ b/tests/Makefile
 @@ -, +, @@ gcov-files-i386-y += hw/block/hd-geometry.c
  check-qtest-i386-y += tests/boot-order-test$(EXESUF)
  check-qtest-i386-y += tests/acpi-test$(EXESUF)
  check-qtest-i386-y += tests/rtc-test$(EXESUF)
 +check-qtest-i386-y += tests/cwd-test$(EXESUF)
  check-qtest-i386-y += tests/i440fx-test$(EXESUF)
  check-qtest-i386-y += tests/fw_cfg-test$(EXESUF)
  check-qtest-i386-y += tests/blockdev-test$(EXESUF)
 @@ -, +, @@ libqos-pc-obj-y += tests/libqos/malloc-pc.o
  libqos-omap-obj-y = $(libqos-obj-y) tests/libqos/i2c-omap.o

  tests/rtc-test$(EXESUF): tests/rtc-test.o
 +tests/cwd-test$(EXESUF): tests/cwd-test.o
  tests/m48t59-test$(EXESUF): tests/m48t59-test.o
  tests/endianness-test$(EXESUF): tests/endianness-test.o
  tests/spapr-phb-test$(EXESUF): tests/spapr-phb-test.o $(libqos-obj-y)
 diff --git a/tests/cwd-test.c b/tests/cwd-test.c
 new file mode
 index ..380a313
 --- /dev/null
 +++ b/tests/cwd-test.c
 @@ -, +, @@
 +/*
 + * QTest testcase for the CSTL Watchdog
 + *
 + * This work is licensed under the terms of the GNU GPL, version 2 or later.
 + * See the COPYING file in the top-level directory.
 + *
 + */
 +#include "libqtest.h"
 +#include "hw/pci/pci_ids.h"
 +#include "hw/pci/pci_regs.h"
 +
 +#include <glib.h>
 +#include <unistd.h>
 +
 +static uint32_t pci_config_read(uint8_t bus, uint8_t devfn,
 +                                uint8_t addr, int size)
 +{
 +    outl(0xcf8, (bus << ) | (devfn << ) | addr | (1u << ));
 +    if (size == ) {
 +        return inb(0xcfc);
 +    } else if (size == ) {
 +        return inw(0xcfc);
 +    }
 +    return inl(0xcfc);
 +}
 +
 +static void pci_config_write(uint8_t bus, uint8_t devfn,
 +                             uint32_t addr, int size, uint32_t value)
 +{
 +    outl(0xcf8, (bus << ) | (devfn << ) | addr | (1u << ));
 +    if (size == ) {
 +        outb(0xcfc, value);
 +    } else if (size == ) {
 +        outw(0xcfc, value);
 +    } else {
 +        outl(0xcfc, value);
 +    }
 +}
 +
 +static void cwd_probe(uint8_t bus, uint8_t devfn)
 +{
 +    uint32_t bar0 = 0xc000;
 +    int i;
 +
 +    pci_config_write(bus, devfn, PCI_COMMAND, ,
 +                     (PCI_COMMAND_IO | PCI_COMMAND_MEMORY));
 +    pci_config_write(bus, devfn, PCI_BASE_ADDRESS_0, , bar0);
 +
 +    g_assert_cmpint(inb(bar0 + 0x00), ==, 0x42);
 +
 +    outb(bar0 + 0x01, 0x03); // activate device
 +    g_assert_cmpint(inb(bar0 + 0x01), ==, 0x01); // confirm activation
 +
 +    for (i = ; i <  * ; i++) {
 +        outb(bar0 + 0x02, 0x32);
 +        g_usleep();
 +    }
 +
 +    outb(bar0 + 0x01, 0x00); // deactivate device
 +}
 +
 +static void basic_init(void)
 +{
 +    int slot;
 +
 +    for (slot = ; slot < ; slot++) {
 +        uint8_t fn;
 +
 +        for (fn = ; fn < ; fn++) {
 +            uint8_t devfn = (slot << ) | fn;
 +            uint16_t device_id;
 +            uint16_t vendor_id;
 +
 +            vendor_id = pci_config_read(, devfn, PCI_VENDOR_ID, );
 +            device_id = pci_config_read(, devfn, PCI_DEVICE_ID, );
 +
 +            if (vendor_id == 0xFFFF || device_id == 0xFFFF) {
 +                break;
 +            }
 +
 +            if (vendor_id == 0x1af4 && device_id == 0x0101) {
 +                cwd_probe(, devfn);
 +                return;
 +            }
 +        }
 +    }
 +
 +    g_assert_not_reached();
 +}
 +
 +int main(int argc, char **argv)
 +{
 +    QTestState *s = NULL;
 +    char *cmd;
 +    int ret;
 +
 +    g_test_init(&argc, &argv, NULL);
 +
 +    cmd = g_strdup_printf("-device cstl-watchdog,expiration-ticks=%d",
 +                          g_test_rand_int_range(, ));
 +
 +    s = qtest_start(cmd);
 +
 +    g_free(cmd);
 +
 +    qtest_add_func("/basic/init", basic_init);
 +
 +    ret = g_test_run();
 +
 +    if (s) {
 +        qtest_quit(s);
 +    }
 +
 +    return ret;
 +}