Re: [PATCH qemu v9] spapr: Implement Open Firmware client interface

[David Gibson <david@gibson.dropbear.id.au>]

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On Thu, Jul 16, 2020 at 07:04:56PM +1000, Alexey Kardashevskiy wrote:
> Ping? I kinda realize it is not going to replace SLOF any time soon but
> still...

Yeah, I know.   I just haven't had time to consider it.  Priority
starvation.

> On 07/07/2020 10:34, Alexey Kardashevskiy wrote:
> > Ping?
> > 
> > 
> > On 24/06/2020 10:28, Alexey Kardashevskiy wrote:
> >> Ping?
> >>
> >> On 02/06/2020 21:40, Alexey Kardashevskiy wrote:
> >>> Ping?
> >>>
> >>> On 13/05/2020 13:58, Alexey Kardashevskiy wrote:
> >>>> The PAPR platform which describes an OS environment that's presented by
> >>>> a combination of a hypervisor and firmware. The features it specifies
> >>>> require collaboration between the firmware and the hypervisor.
> >>>>
> >>>> Since the beginning, the runtime component of the firmware (RTAS) has
> >>>> been implemented as a 20 byte shim which simply forwards it to
> >>>> a hypercall implemented in qemu. The boot time firmware component is
> >>>> SLOF - but a build that's specific to qemu, and has always needed to be
> >>>> updated in sync with it. Even though we've managed to limit the amount
> >>>> of runtime communication we need between qemu and SLOF, there's some,
> >>>> and it has become increasingly awkward to handle as we've implemented
> >>>> new features.
> >>>>
> >>>> This implements a boot time OF client interface (CI) which is
> >>>> enabled by a new "x-vof" pseries machine option (stands for "Virtual Open
> >>>> Firmware). When enabled, QEMU implements the custom H_OF_CLIENT hcall
> >>>> which implements Open Firmware Client Interface (OF CI). This allows
> >>>> using a smaller stateless firmware which does not have to manage
> >>>> the device tree.
> >>>>
> >>>> The new "vof.bin" firmware image is included with source code under
> >>>> pc-bios/. It also includes RTAS blob.
> >>>>
> >>>> This implements a handful of CI methods just to get -kernel/-initrd
> >>>> working. In particular, this implements the device tree fetching and
> >>>> simple memory allocator - "claim" (an OF CI memory allocator) and updates
> >>>> "/memory@0/available" to report the client about available memory.
> >>>>
> >>>> This implements changing some device tree properties which we know how
> >>>> to deal with, the rest is ignored. To allow changes, this skips
> >>>> fdt_pack() when x-vof=on as not packing the blob leaves some room for
> >>>> appending.
> >>>>
> >>>> In absence of SLOF, this assigns phandles to device tree nodes to make
> >>>> device tree traversing work.
> >>>>
> >>>> When x-vof=on, this adds "/chosen" every time QEMU (re)builds a tree.
> >>>>
> >>>> This adds basic instances support which are managed by a hash map
> >>>> ihandle -> [phandle].
> >>>>
> >>>> Before the guest started, the used memory is:
> >>>> 0..4000 - the initial firmware
> >>>> 10000..180000 - stack
> >>>>
> >>>> This OF CI does not implement "interpret".
> >>>>
> >>>> With this basic support, this can only boot into kernel directly.
> >>>> However this is just enough for the petitboot kernel and initradmdisk to
> >>>> boot from any possible source. Note this requires reasonably recent guest
> >>>> kernel with:
> >>>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=df5be5be8735
> >>>>
> >>>> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
> >>>> ---
> >>>>
> 
> 

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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