Re: [PATCH for-4.22 v2 0/2] xen/arm: validate hwdom first bank boot placement

["Orzel, Michal" <michal.orzel@xxxxxxx>]

On 05-Jun-26 10:00, Oleksii Kurochko wrote:
> Hello Mykola,
> 
> On 6/5/26 7:19 AM, Mykola Kvach wrote:
>> From: Mykola Kvach <mykola_kvach@xxxxxxxx>
> 
> Just out of curiosity, is it okay that the email address listed here 
> differs from the one you're using to send patches? (By the way, nice 
> email address ;))
> 
>>
>> With LLC coloring enabled, the hardware domain memory is allocated by
>> allocate_hwdom_memory() instead of relying on the fixed direct-map
>> layout. Since de99f3263555 ("device-tree: Improve hwdom memory
>> allocation for DMA"), the allocator prefers lower host regions, but the
>> first-bank filter still only enforces the old 128MB heuristic.
>>
>> A low candidate bank can satisfy that heuristic while still being
>> unsuitable for the Arm kernel/DTB/initrd placement rules. Split the Arm
>> placement logic into reusable helpers first, then validate the candidate
>> hardware-domain bank 0 against those helpers before allocating it.
>>
>> Changes in v2:
>> - Split the previous single patch into a behavior-preserving Arm
>>    placement refactoring and a separate hardware-domain first-bank fix.
>> - Rename find_module_placement() and place_modules() to use DTB/initrd
>>    terminology.
>> - Pass ramend to find_dtb_initrd_placement().
>> - Update the stale tools/libs/guest/xg_dom_arm.c reference.
>>
>> Link to v1:
>>    
>> https://patchew.org/Xen/4f862bb2dc323914b8120b0f16af7516140cf42b.1780065103.git.mykola._5Fkvach@xxxxxxxx/
>>
> 
> I would like to clarify whether my understanding is correct.
> 
> With LLC coloring enabled on ARM, the allocator could assign the 
> hardware domain a bank 0 that passes the size check but is unsuitable 
> for kernel/DTB/initrd placement. As a result, the hardware domain may 
> fail to boot or could silently corrupt memory if the images are placed 
> in an incorrect location.
> 
> Is my understanding correct?
Yes, Xen would fail to boot such domain. On Arm we carry a lot of placement
logic we need to deal with...

~Michal