|
From: | Alexey Kardashevskiy |
Subject: | Re: [PATCH for-7.2 v2 10/20] hw/ppc: set machine->fdt in spapr machine |
Date: | Tue, 23 Aug 2022 18:58:10 +1000 |
User-agent: | Mozilla/5.0 (X11; Linux x86_64; rv:104.0) Gecko/20100101 Thunderbird/104.0 |
On 22/08/2022 20:30, Daniel Henrique Barboza wrote:
On 8/22/22 00:29, Alexey Kardashevskiy wrote:On 22/08/2022 13:05, David Gibson wrote:On Fri, Aug 19, 2022 at 06:42:34AM -0300, Daniel Henrique Barboza wrote:On 8/18/22 23:11, Alexey Kardashevskiy wrote:On 05/08/2022 19:39, Daniel Henrique Barboza wrote:The pSeries machine never bothered with the common machine->fdt attribute. We do all the FDT related work using spapr->fdt_blob. We're going to introduce HMP commands to read and save the FDT, which will rely on setting machine->fdt properly to work across all machine archs/types.Out of curiosity - why new HMP command, is not QOM'ing this ms::fdt property enough?I tried to do the minimal changes needed for the commands to work. ms::fdt isone of the few MachineState fields that hasn't been QOMified bymachine_class_init() yet. All pre-existing code that uses ms::fdt are using the pointer directly. To make a QOMified use of it would require extra patchesin machine.c to QOMify the property first.There's also the issue with how each machine is creating the FDT. Most are using helpers from device_tree.c, some are creating it from scratch, others required a .dtb file, most of them are not doing a fdt_pack() and so on. To really QOMify the use of ms::fdt we would need some machine hooks that standardize all that.I believe it's worth the trouble, but it would be too much to do right now.Hmm.. I think this depends on what you mean by "QOM"ify exactly. If you're meaning make the full DT representation QOM objects, that you can look into in detail, then, yes, that's pretty complicated. I suspect what Alexey was suggesting though, was merely to make ms::fdt accessible as a single bytestring property on the machine QOM object. Effectively it's just "dumpdtb" but as a property get.Yes, I meant the bytestream, as DTC can easily decompile it onto a DTS.I'm not 100% certain if QOM can safely represent arbitrary bytestrings as QOM properties, which would need checking.I am not sure either but rather than adding another command to HMP, I'd explore this option first.I'm not sure what you mean by that. The HMP version of 'dumpdtb' is more flexible that the current "-machine dumpdtb", an extra machine option that would causethe guest to exit after writing the dtb
True. Especially with CAS :)
And 'info fdt' is a new command thatmakes it easier to inspect specific nodes/props.
btw what is this new command going to do? decompile the tree or save dtb?
I don't see how making ms::fdt being retrievable by object_property_get() internally (remember that ms::fdt it's not fully QOMified, so there's no introspection of its value from the QEMU monitor) would make any of these new HMP commands obsolete.
Well, there are QMP and HMP and my feeling was that HMP is slowly getting deprecated or something and QMP is the superior one. So I thought since this FDT is a property and there is no associated action with it, making it a property would do.
For ages I've been using a python3 script to talk to QMP as HMP is really quite limited, the only thing in HMP which is not in QMP is dumping memory ("x", "xp"), in this case I wrap HMP into QMP and keep using QMP :)
Thanks, Daniel
-- Alexey
[Prev in Thread] | Current Thread | [Next in Thread] |