Re: [PATCH v2 5/5] xen/memory, tools: Make init-dom0less consume XEN_DOMCTL_get_mem_map

[Jan Beulich <jbeulich@xxxxxxxx>]

On 12.03.2024 04:44, Henry Wang wrote:
> On 3/12/2024 1:07 AM, Jan Beulich wrote:
>> On 08.03.2024 02:54, Henry Wang wrote:
>>> --- a/xen/include/public/memory.h
>>> +++ b/xen/include/public/memory.h
>>> @@ -41,6 +41,11 @@
>>>   #define XENMEMF_exact_node(n) (XENMEMF_node(n) | 
>>> XENMEMF_exact_node_request)
>>>   /* Flag to indicate the node specified is virtual node */
>>>   #define XENMEMF_vnode  (1<<18)
>>> +/*
>>> + * Flag to force populate physmap to use pages from domheap instead of 1:1
>>> + * or static allocation.
>>> + */
>>> +#define XENMEMF_force_heap_alloc  (1<<19)
>>>   #endif
>> If this is for populate_physmap only, then other sub-ops need to reject
>> its use.
>>
>> I have to admit I'm a little wary of allocating another flag here and ...
>>
>>> --- a/xen/include/xen/mm.h
>>> +++ b/xen/include/xen/mm.h
>>> @@ -205,6 +205,8 @@ struct npfec {
>>>   #define  MEMF_no_icache_flush (1U<<_MEMF_no_icache_flush)
>>>   #define _MEMF_no_scrub    8
>>>   #define  MEMF_no_scrub    (1U<<_MEMF_no_scrub)
>>> +#define _MEMF_force_heap_alloc 9
>>> +#define  MEMF_force_heap_alloc (1U<<_MEMF_force_heap_alloc)
>>>   #define _MEMF_node        16
>>>   #define  MEMF_node_mask   ((1U << (8 * sizeof(nodeid_t))) - 1)
>>>   #define  MEMF_node(n)     ((((n) + 1) & MEMF_node_mask) << _MEMF_node)
>> ... here - we don't have that many left. Since other sub-ops aren't
>> intended to support this flag, did you consider adding another (perhaps
>> even arch-specific) sub-op instead?
> 
> Not really, I basically followed the discussion from [1] to implement 
> this patch. However I understand your concern. Just want to make sure if 
> I understand your suggestion correctly, by "adding another sub-op" you 
> mean adding a sub-op similar as "XENMEM_populate_physmap" but only with 
> executing the "else" part I want, so we can drop the use of these two 
> added flags? Thanks!
> 
> [1] 
> https://lore.kernel.org/xen-devel/3982ba47-6709-47e3-a9c2-e2d3b4a2d8e3@xxxxxxx/

In which case please check with Julien (and perhaps other Arm maintainers)
before deciding on whether to go this alternative route.

Jan