[PATCH v6 3/7] lib: Support ARCH_HAS_CPU_CACHE_INVALIDATE_MEMREGION

[Conor Dooley]

On Mon, Nov 17, 2025 at 10:51:11AM -0800, Randy Dunlap wrote:
> Hi,
> 
> On 11/17/25 2:47 AM, Jonathan Cameron wrote:
> > diff --git a/lib/Kconfig b/lib/Kconfig
> > index e629449dd2a3..e11136d188ae 100644
> > --- a/lib/Kconfig
> > +++ b/lib/Kconfig
> > @@ -542,6 +542,10 @@ config MEMREGION
> >  config ARCH_HAS_CPU_CACHE_INVALIDATE_MEMREGION
> >  	bool
> >  
> > +config GENERIC_CPU_CACHE_MAINTENANCE
> > +	bool
> > +	select ARCH_HAS_CPU_CACHE_INVALIDATE_MEMREGION
> > +
> >  config ARCH_HAS_MEMREMAP_COMPAT_ALIGN
> >  	bool
> 
> Architectures and/or platforms select ARCH_HAS_*.
> 
> With this change above, it becomes the only entry in
> lib/Kconfig that does "select ARCH_HAS_anytning".
> 
> so I think this is wrong, back*wards.

Maybe it is backwards, but I feel like this way is more logical. ARM64
has memregion invalidation only because this generic approach is
enabled, so the arch selects what it needs to get the support.
Alternatively, something like
| diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
| index 5f7f63d24931..75b2507f7eb2 100644
| --- a/arch/arm64/Kconfig
| +++ b/arch/arm64/Kconfig
| @@ -21,6 +21,7 @@ config ARM64
|  	select ARCH_ENABLE_THP_MIGRATION if TRANSPARENT_HUGEPAGE
|  	select ARCH_HAS_CACHE_LINE_SIZE
|  	select ARCH_HAS_CC_PLATFORM
| +	select ARCH_HAS_CPU_CACHE_INVALIDATE_MEMREGION
|  	select ARCH_HAS_CURRENT_STACK_POINTER
|  	select ARCH_HAS_DEBUG_VIRTUAL
|  	select ARCH_HAS_DEBUG_VM_PGTABLE
| @@ -146,7 +147,6 @@ config ARM64
|  	select GENERIC_ARCH_TOPOLOGY
|  	select GENERIC_CLOCKEVENTS_BROADCAST
|  	select GENERIC_CPU_AUTOPROBE
| -	select GENERIC_CPU_CACHE_MAINTENANCE
|  	select GENERIC_CPU_DEVICES
|  	select GENERIC_CPU_VULNERABILITIES
|  	select GENERIC_EARLY_IOREMAP
| diff --git a/lib/Kconfig b/lib/Kconfig
| index 09aec4a1e13f..ac223e627bc5 100644
| --- a/lib/Kconfig
| +++ b/lib/Kconfig
| @@ -544,8 +544,9 @@ config ARCH_HAS_CPU_CACHE_INVALIDATE_MEMREGION
|  	bool
|  
|  config GENERIC_CPU_CACHE_MAINTENANCE
| -	bool
| -	select ARCH_HAS_CPU_CACHE_INVALIDATE_MEMREGION
| +	def_bool y
| +	depends on ARCH_HAS_CPU_CACHE_INVALIDATE_MEMREGION
| +	depends on ARM64
|  
|  config ARCH_HAS_MEMREMAP_COMPAT_ALIGN
|  	bool
implies (to me at least) that arm64 has memregion invalidation as an
architectural feature and that the GENERIC_CPU_CACHE_MAINTENANCE option
is a just common cross-arch code, like generic entry etc, rather than
being the option gating the drivers that provide the feature in the
first place.

I didn't really care which way it went, and was gonna post something to
squash and avoid another revision, but I found the resultant Kconfig
setup to be make less sense to me than what came before. If the switched
around version is less likely to be problematic etc, then sure, but I
amn't convinced by switching it at a first glance.
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