linux-kernel - Re: [PATCH v4 00/30] Live Update Orchestrator

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Message-ID: <20251007175038.GB3474167@nvidia.com>
Date: Tue, 7 Oct 2025 14:50:38 -0300
From: Jason Gunthorpe <jgg@...dia.com>
To: Pasha Tatashin <pasha.tatashin@...een.com>
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Subject: Re: [PATCH v4 00/30] Live Update Orchestrator

On Tue, Oct 07, 2025 at 01:10:30PM -0400, Pasha Tatashin wrote:
> 
> 1. Add three more callbacks to liveupdate_file_ops:
> /*
>  * Optional. Called by LUO during first get global state call.
>  * The handler should allocate/KHO preserve its global state object and return a
>  * pointer to it via 'obj'. It must also provide a u64 handle (e.g., a physical
>  * address of preserved memory) via 'data_handle' that LUO will save.
>  * Return: 0 on success.
>  */
> int (*global_state_create)(struct liveupdate_file_handler *h,
>                            void **obj, u64 *data_handle);
> 
> /*
>  * Optional. Called by LUO in the new kernel
>  * before the first access to the global state. The handler receives
>  * the preserved u64 data_handle and should use it to reconstruct its
>  * global state object, returning a pointer to it via 'obj'.
>  * Return: 0 on success.
>  */
> int (*global_state_restore)(struct liveupdate_file_handler *h,
>                             u64 data_handle, void **obj);

It shouldn't be a "push" like this. Everything has a certain logical point
when it will need the luo data, it should be coded to 'pull' the data
right at that point.


> /*
>  * Optional. Called by LUO after the last
>  * file for this handler is unpreserved or finished. The handler
>  * must free its global state object and any associated resources.
>  */
> void (*global_state_destroy)(struct liveupdate_file_handler *h, void *obj);

I'm not sure a callback here is a good idea, the users are synchronous
at early boot, they should get their data and immediately process it
within the context of the caller. A 'unpack' callback does not seem so
useful to me.

> The get/put global state data:
> 
> /* Get and lock the data with file_handler scoped lock */
> int liveupdate_fh_global_state_get(struct liveupdate_file_handler *h,
>                                    void **obj);
> 
> /* Unlock the data */
> void liveupdate_fh_global_state_put(struct liveupdate_file_handler *h);

Maybe lock/unlock if it is locking.

It seems like a good direction overall. Really need to see how it
works with some examples

Jason