Re: [PATCH v3] hw/i386: place setup_data at fixed place in memory

[Ard Biesheuvel]

On Fri, 5 Aug 2022 at 10:10, Paolo Bonzini <pbonzini@redhat.com> wrote:
>
> On 8/5/22 01:04, Jason A. Donenfeld wrote:
> > +    /* Nothing else uses this part of the hardware mapped region */
> > +    setup_data_base = 0xfffff - 0x1000;
>
> Isn't this where the BIOS lives?  I don't think this works.
>
> Does it work to place setup_data at the end of the cmdline file instead
> of having it at the end of the kernel file?  This way the first item
> will be at 0x20000 + cmdline_size.
>

Does QEMU always allocate the command line statically like that?
AFAIK, OVMF never accesses that memory to read the command line, it
uses fw_cfg to copy it into a buffer it allocates itself. And I guess
that implies that this region could be clobbered by OVMF unless it is
told to preserve it.