Blue Swirl writes:
> 2011/9/29 Lluís Vilanova <vilan...@ac.upc.edu>:
>> +static uint64_t control_io_read(void *opaque, target_phys_addr_t addr,
>> unsigned size)
>> +{
>> + State *s = opaque;
>> +
>> + uint64_t res = ldq_p(&s->size);
>> + uint8_t *resb = (uint8_t*)&res;
>> + return resb[addr % CTRL_BYTES];
> I don't think these lines do what you mean, but I'm also not sure what
> it is supposed to mean.
Pre: only can read on a byte-per-byte basis (as stated in control_ops.impl),
just because the code looks less ugly, and host performance should not be an
issue here.
The device is treated as a circular buffer of length CTRL_BYTES
Reads are only used to get the size of the data channel.
First line should handle guest/host endianess swapping, although I'm not sure if
that's the API I'm supposed to use.
Then return the N'th byte of the uint64_t variable holding the (endianess-aware)
result.
>> +}
>> +
>> +static void control_io_write(void *opaque, target_phys_addr_t addr,
>> uint64_t data, unsigned size)
>> +{
>> + State *s = opaque;
>> +
>> + uint8_t *cmdb = (uint8_t*)&s->cmd;
>> + cmdb[addr % CTRL_BYTES] = (uint8_t)data;
>> +
>> + if ((addr + size) % CTRL_BYTES == 0) {
>> + qemu_backdoor(ldq_p(&s->cmd), s->data_ptr);
>> + }
> Same here.
Pre: same as during reads.
Accumulates writes into s->cmd to build the command the guest is sending us (in
guest endianess).
When CTRL_BYTES bytes have been written into the device, get the command value
into host endianess and invoke the user-provided backdoor callback.
This assumes that when executing in KVM, the device handling infrastructure will
get a lock and only one CPU will be sending a backdoor command until completion.
I'll add some comments there and prefix all structs and functions with
"backdoor_", as otherwise debugging could get harder if everyone started
avoiding the prefixes.
Lluis
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