Re: [PATCH v7 03/38] x86/boot: move headroom to boot modules

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 21/10/2024 1:45 am, Daniel P. Smith wrote:
> The purpose of struct boot_module is to encapsulate the state of boot module 
> as
> it is processed by Xen. Locating boot module state struct boot_module reduces
> the number of global variables as well as the number of state variables that
> must be passed around. It also lays the groundwork for hyperlaunch mult-domain
> construction, where multiple instances of state variables like headroom will 
> be
> needed.
>
> Signed-off-by: Daniel P. Smith <dpsmith@xxxxxxxxxxxxxxxxxxxx>
> Reviewed-by: Jason Andryuk <jason.andryuk@xxxxxxx>

Actually, based on the observation in the subsequent patch about pulling
the initial_image deletion earlier in the series, I'm going to recommend
something else here.

You should fully remove the mod pointer in __start_xen() (i.e. convert
mod[] references to bi->mods[]) before starting to remove other
variables such as module_headroom here.

This is largely doable because microcode and xsm both take the mbi
pointer and map mbi->module_addr themselves, rather than take
__start_xen()'s pointer.

Again, this reduces churn in the series, and minimises the extent to
which we're operating on multiple representations of the same data.

~Andrew