Re: [PATCH v2 1/3] arm64: mm: Fix rodata=full block mapping support for realm guests

[Ryan Roberts]

On 03/04/2026 11:31, Catalin Marinas wrote:
> On Thu, Apr 02, 2026 at 09:43:59PM +0100, Catalin Marinas wrote:
>> Another thing I couldn't get my head around - IIUC is_realm_world()
>> won't return true for map_mem() yet (if in a realm). Can we have realms
>> on hardware that does not support BBML2_NOABORT? We may not have
>> configuration with rodata_full set (it should be complementary to realm
>> support).
> 
> With rodata_full==false, can_set_direct_map() returns false initially
> but after arm64_rsi_init() it starts returning true if is_realm_world().
> The side-effect is that map_mem() goes for block mappings and
> linear_map_requires_bbml2 set to false. Later on,
> linear_map_maybe_split_to_ptes() will skip the splitting.
> 
> Unless I'm missing something, is_realm_world() calls in
> force_pte_mapping() and can_set_direct_map() are useless. I'd remove
> them and either require BBML2_NOABORT with CCA or get the user to force
> rodata_full when running in realms. Or move arm64_rsi_init() even
> earlier?

I'd need Suzuki to comment on this. As I said in the other mail, I was treating
this like a pre-existing bug. But I guess linear_map_requires_bbml2 ending up
wrong is a problem here. I'm not sure it's quite as simple as requiring
BBML2_NOABORT with CCA as we still need can_set_direct_map() to return true if
we are in a realm.

I don't know what it would take to run arm64_rsi_init() even earlier, but that
would be the best option from my point of view.

Thanks,
Ryan