Re: [PATCH RFC v1] hw/i386: place setup_data at fixed place in memory

["Jason A. Donenfeld" <Jason@zx2c4.com>]

Hi Michael,

On Wed, Aug 03, 2022 at 06:25:39PM -0400, Michael S. Tsirkin wrote:
> > -    /* Offset 0x250 is a pointer to the first setup_data link. */
> > -    stq_p(header + 0x250, first_setup_data);
> > +    if (first_setup_data) {
> > +            /* Offset 0x250 is a pointer to the first setup_data link. */
> > +            stq_p(header + 0x250, first_setup_data);
> > +            rom_add_blob("setup_data", setup_datas, setup_data_total_len, setup_data_total_len,
> > +                         SETUP_DATA_PHYS_BASE, NULL, NULL, NULL, NULL, false);
> > +    }
> > +
> >
> 
> Allocating memory on x86 is tricky business.  Can we maybe use bios-linker-loader
> with COMMAND_WRITE_POINTER to get an address from firmware?

Hmm. Is BIOSLinker even available to us at this stage in preparation?

One thing to note is that this memory doesn't really need to be
persistent. It's only used extreeeemely early in boot. So it could be
somewhere that gets used/remapped later on.

Jason