Re: [PATCH v1 6/9] asm-generic: move some parts of Arm's domain_build.h to asm-generic header

[Jan Beulich <jbeulich@xxxxxxxx>]

On 03.02.2025 16:50, Oleksii Kurochko wrote:
> On 1/27/25 12:23 PM, Jan Beulich wrote:
>> On 08.01.2025 12:13, Oleksii Kurochko wrote:
>>> Nothing changed. Only some functions declaration are moved to asm-generic
>>> header as they are expected to be used by common code of domain builing or
>>> dom0less.
>>>
>>> Signed-off-by: Oleksii Kurochko<oleksii.kurochko@xxxxxxxxx>
>>> ---
>>>   xen/arch/arm/include/asm/domain_build.h | 19 ++----------
>>>   xen/include/asm-generic/domain-build.h  | 41 +++++++++++++++++++++++++
>>>   2 files changed, 43 insertions(+), 17 deletions(-)
>>>   create mode 100644 xen/include/asm-generic/domain-build.h
>> Again I question this movement under this name. "Domain building" is a pretty
>> generic thing, yes, but what you move would e.g. be entirely inapplicable on
>> x86 (as it is now). For example ...
>>
>>> --- /dev/null
>>> +++ b/xen/include/asm-generic/domain-build.h
>>> @@ -0,0 +1,41 @@
>>> +/* SPDX-License-Identifier: GPL-2.0-only */
>>> +#ifndef __ASM_GENERIC_DOMAIN_BUILD_H__
>>> +#define __ASM_GENERIC_DOMAIN_BUILD_H__
>>> +
>>> +#include <xen/types.h>
>>> +
>>> +struct domain;
>>> +struct page_info;
>>> +struct kernel_info;
>>> +struct membanks;
>>> +
>>> +typedef bool (*alloc_domheap_mem_cb)(struct domain *d, struct page_info 
>>> *pg,
>>> +                                     unsigned int order, void *extra);
>>> +bool allocate_domheap_memory(struct domain *d, paddr_t tot_size,
>>> +                             alloc_domheap_mem_cb cb, void *extra);
>>> +
>>> +bool allocate_bank_memory(struct kernel_info *kinfo, gfn_t sgfn,
>>> +                          paddr_t tot_size);
>> ... the term "bank" seems pretty closely tied to DT. Other stuff ...
>>
>>> +void allocate_memory(struct domain *d, struct kernel_info *kinfo);
>>> +int construct_domain(struct domain *d, struct kernel_info *kinfo);
>>> +int make_chosen_node(const struct kernel_info *kinfo);
>>> +int make_cpus_node(const struct domain *d, void *fdt);
>>> +int make_hypervisor_node(struct domain *d, const struct kernel_info *kinfo,
>>> +                         int addrcells, int sizecells);
>>> +int make_memory_node(const struct kernel_info *kinfo, int addrcells,
>>> +                     int sizecells, const struct membanks *mem);
>>> +int make_timer_node(const struct kernel_info *kinfo);
>> ... here also falls in this category. Stuff like this may well live
>> under asm-generic/, but the file name chosen then needs to reflect
>> constraints.
> 
> Unfortunately, at least at the moment, this is not applicable to x86.
> 
> Partially, domain_build.h was chosen to have less changes in Arm code.
> 
> Would it be better to use domain-build-dt.h?

That would at least be a more specific name. Yet then - why put such under
asm-generic/ ? This stuff isn't truly generic (as in: any arch can fall
back to using this). Personally I'd rather expect such stuff to live under
e.g. include/xen/device-tree/. That would make it clear that environments
using DT may consider using it, but other environment shouldn't.

Jan