[Qemu-devel] loadvm not working

[Qemu-devel] loadvm not working

[Piotras]

Hi,

I discovered a bug that prevents loadvm from working correctly
in current repository version (related to warning "qemu: warning:
instance 0 of device '' not present in current VM").

The implementation of functions qemu_get_be16 and qemu_get_be32
(in file vl.c) relies on implicit conversion of signed byte
(int8_t) values returned by qemu_get_byte to multi-byte integer
types. When value to be converted is negative, the result is
incorrect.

There are two fixes possible:

1) change return type of qemu_get_byte to unsigned (uint8_t)

2) add explicit casts in qemu_get_be16 and qemu_get_be32

For consistency with qemu_get_be16 and qemu_get_be32, first
solution looks better. However I didn't examine all other calls
to qemu_get_byte for possible problems.


Hope this helps,

Piotr

Re: [Qemu-devel] loadvm not working

[Anthony Liguori]

Piotras wrote:
> Hi,
>
> I discovered a bug that prevents loadvm from working correctly
> in current repository version (related to warning "qemu: warning:
> instance 0 of device '' not present in current VM").
> The implementation of functions qemu_get_be16 and qemu_get_be32
> (in file vl.c) relies on implicit conversion of signed byte
> (int8_t) values returned by qemu_get_byte to multi-byte integer
> types. When value to be converted is negative, the result is
> incorrect.
>
> There are two fixes possible:
>
> 1) change return type of qemu_get_byte to unsigned (uint8_t)
>
> 2) add explicit casts in qemu_get_be16 and qemu_get_be32
>
> For consistency with qemu_get_be16 and qemu_get_be32, first
> solution looks better. However I didn't examine all other calls
> to qemu_get_byte for possible problems.
>   

Heh, I literally just debugged this myself :-)  That patch that 
introduced this is being reverted so it'll be fixed in a few hours.

Regards,

Anthony Liguori

> Hope this helps,
>
> Piotr
>
>
>