Re: [Qemu-devel] Help writing a trivial device

[Zhi Yong Wu]

2011/9/26 Lluís Vilanova <address@hidden>:
> Hi. I started writing a trivial device on QEMU that should get called on every
> read and write on the memory it provides.
>
> The problems are that:
>
> 1) Cannot start QEMU with KVM when the device is enabled:
>       kvm_set_phys_mem: error registering slot: Invalid argument
>
> 2) The driver never gets called on a read/write to its memory
>
> I'm sure this is due to some error in my code, but I'm clueless as to what it
> could be.
>
>
> The testing system is a Linux 2.6.32, with this:
>
> int fd = open("/sys/devices/pci0000:00/000000:00:004.00/resource0", O_RDWR);
> void *addr = mmap(NULL, 4096, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
> printf("-> %ld\n", *(uint64_t*)addr);
This is the way about how to test bar? Does bar1 correspond to guest
file /sys/devices/pci0000:00/000000:00:004.00/resource0?

>
>
> The device is something like (some code changed for brevity):
>
> typedef struct State
> {
>    PCIDevice dev;
>    MemoryRegion control;
> } State;
>
>
> static uint64_t control_io_read(void *opaque, target_phys_addr_t addr, 
> unsigned size)
> {
>    return 0xcafe;
> }
>
> static void control_io_write(void *opaque, target_phys_addr_t addr, uint64_t 
> data, unsigned size)
> {
>    /* do something */
> }
>
> static const MemoryRegionOps control_ops = {
>    .read = control_io_read,
>    .write = control_io_write,
>    .endianness = DEVICE_NATIVE_ENDIAN,
>    .valid = {
>        .min_access_size = 8,
>        .max_access_size = 8,
>    },
> };
>
>
> static int init(PCIDevice *dev)
> {
>    State *s = DO_UPCAST(State, dev, dev);
>
>    memory_region_init_io(&s->control, &control_ops, s, "backdoor.control",
>                          TARGET_PAGE_SIZE);
>    pci_register_bar(&s->dev, 0, PCI_BASE_ADDRESS_SPACE_MEMORY, &s->control);
>
>    return 0;
> }
>
> static int fini(PCIDevice *dev)
> {
>    State *s = DO_UPCAST(State, dev, dev);
>
>    memory_region_destroy(&s->control);
>
>    return 0;
> }
>
>
> static PCIDeviceInfo info = {
>    .qdev.name  = "foo",
>    .qdev.size  = sizeof(State),
>    .init       = init,
>    .exit       = fini,
>    .vendor_id  = PCI_VENDOR_ID_REDHAT_QUMRANET,
>    .device_id  = 0x1005,
>    .class_id   = PCI_CLASS_MEMORY_RAM,
> };
>
> static void register_devices(void)
> {
>    pci_qdev_register(&info);
> }
>
> device_init(register_devices)
>
>
>
> Is there something blatantly wrong in the device code?
>
>
> Thanks a lot,
>    Lluis
>
> --
>  "And it's much the same thing with knowledge, for whenever you learn
>  something new, the whole world becomes that much richer."
>  -- The Princess of Pure Reason, as told by Norton Juster in The Phantom
>  Tollbooth
>
>



-- 
Regards,

Zhi Yong Wu