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

[Avi Kivity]

On 09/26/2011 03:54 PM, Lluís Vilanova wrote:
> It is the second bar that generates the problems with KVM:
>
>      s->data_ptr = g_malloc(s->size);
>      memory_region_init_ram_ptr(&s->data,&s->dev.qdev, "backdoor.data",
>                                 s->size, s->data_ptr);
>      pci_register_bar(&s->dev, 1, PCI_BASE_ADDRESS_SPACE_MEMORY,&s->data);

s->data_ptr is not properly aligned.  Use memory_region_init_ram().

> >  I only had a few minutes and couldn't test reading from BAR0, but you
> >  might want to get 32-bit reads working first before trying 64-bit.
>
> The next problem is using 64bit reads and writes... if I set min_access_size and
> max_access_size to 4, I get the calls to 'control_io_read', but not with 8...

8-byte accesses are not yet supported.

--
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.