CTF: UEFI HTTP boot support

[Rodney W. Grimes]

> 
> > On Jun 17, 2020, at 12:12 PM, Warner Losh <imp at bsdimp.com> wrote:
> > 
> > I missed the start of this thread, so maybe I'm missing a key detail. However, I thought UEFI didn't have a RAM-disk, per se, but that we could load memory areas and pass that into the kernel using freebsd-only methods. But UEFI is a bit weird, so maybe it will generate a virtual cdrom...
> 
> See https://uefi.org/sites/default/files/resources/FINAL%20Pres4%20UEFI%20HTTP%20Boot.pdf
> 
> ? RAM Disk Standard
> 
> ? UEFI 2.5 defined RAM Disk device path nodes
> - Standard access to a RAM Disk in UEFI
> - Supports Virtual Disk and Virtual CD (ISO image) in persistent or
> volatile memory?

Does freeBSD have any way to access these "Virtual Disk"
or Virtual CD images once we leave the world of the loader?
I believe we do not, as these are BIOS/UEFI devices that
require calls into the UEFI code, which, IIRC is gone
once we exit the loader and start the kernel proper,
or shortly there after.

As far as I know these devices well not be found by the FreeBSD
cam layer ATA or AHCI drivers as they do not present an actual
PCI device to find.

> Rebecca Cran
-- 
Rod Grimes                                                 rgrimes at freebsd.org