Re: [Qemu-devel] [RFC 7/7] fw_cfg DMA for x86

["Marc Marí" <markmb@redhat.com>]

On Tue, 21 Jul 2015 18:14:40 +0100
Peter Maydell <peter.maydell@linaro.org> wrote:

> On 21 July 2015 at 17:03, Marc Marí <markmb@redhat.com> wrote:
> > Enable fw_cfg for x86 machines. Create new machine to avoid
> > incompatibilites.
> 
> > @@ -1391,7 +1399,14 @@ FWCfgState *pc_memory_init(MachineState
> > *machine, option_rom_mr,
> >                                          1);
> >
> > -    fw_cfg = bochs_bios_init();
> > +    if (guest_info->fw_cfg_dma) {
> > +        as = g_malloc(sizeof(*as));
> > +        address_space_init(as, ram_below_4g, "pc.as");
> > +        fw_cfg = bochs_bios_init(as, BIOS_CFG_DMA_ADDR);
> > +    } else {
> > +        fw_cfg = bochs_bios_init(NULL, 0);
> > +    }
> > +
> 
> As with ARM: what's the rationale for choosing this particular
> AddressSpace as the target for fw_cfg DMA? (I'm not saying it's
> wrong, necessarily -- I was just surprised we didn't just use
> the system address space.)
> 
> thanks
> -- PMM

I took something that seemed logical for me, as the BIOS will be
working in 32 bits. But, as with ARM, I'm not really sure which
address space should I use for this purpose. I'd appreciate some help
in the issue.

Thanks
Marc