Re: [PATCH qemu v11] spapr: Implement Open Firmware client interface

[Cédric Le Goater]

On 12/7/20 6:15 PM, Greg Kurz wrote:
> On Mon, 7 Dec 2020 18:33:27 +1100
> Alexey Kardashevskiy <aik@ozlabs.ru> 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".
>>
>> Unlike SLOF, this does not format uninitialized nvram. Instead, this
>> includes a disk image with pre-formatted nvram.
>>
> 
> [...]
> 
>> diff --git a/pc-bios/vof/nvram.bin b/pc-bios/vof/nvram.bin
>> new file mode 100644
>> index 
>> 0000000000000000000000000000000000000000..d183901cf980a91d81c4348bb20487c7bb62a2ec
>> GIT binary patch
>> literal 16384
>> zcmeI%Jx;?g6bEpZJ8*)oSZeqZi&Z2pKnD)sI4{AHlNb4;RW}a70XPHaW57uo=-#R7
>> zKSLBhJJ0sdixY3IuY@hzo0r$OmE%T;XE9uh@s1k=AOHafKmY;|fB*y_009U<00Izz
>> z00bZa0SG_<0uX=z1Rwwb2tWV=XCbip6d#B4{{rX#XR%}$Bm^J;0SG|gWP$!?Aq=-I
>> zcT+0Ix{{?1q>9J8r+eW^JK1tYYZZMWQCUwW%0S*~w^p@wfkX-<yRFx)H*+YEt0RRd
>> zmn}6xtwbP`yp4O=>kxMAEA<~5@*g)@mb%KD5!;O~8c)>8rRQBx55=trhk#+1+T3J_
>> zaf*G4vZAduqy$qda{``6Gnc2DQg<Es<GLxL#9<Oj*zP!8ZSnwf@-j7l47!nFXQO$a
>> z^Hes6YU^_M<KsM*k~zwOSa+2g3Sx{*Eyu^XrB0FM5IJ-*?8`VvpBc4}vS(+_UKJ;=
>> xITAns0uX=z1Rwwb2tWV=5P-nt34DD||Nni|VfbXeJORuY0uX=z1R!vE0>7B^s4f5i
>>
>> literal 0
>> HcmV?d00001
>>
> 
> So this needs an extra drive on the command line, eg:
> 
> -drive file=pc-bios/vof/nvram.bin,format=raw,if=pflash
> 
> Any chance this can be generated internally if the user
> didn't provide one already ?

or simply change the bios filename if x-vof=on ? 

C.