Re: [PATCH 07/10] xen/arm: intruduce alloc_domstatic_pages

[Julien Grall <julien@xen.org>]

Hi Penny,

On 18/05/2021 09:57, Penny Zheng wrote:
>> -----Original Message-----
>> From: Jan Beulich <jbeulich@suse.com>
>> Sent: Tuesday, May 18, 2021 3:35 PM
>> To: Penny Zheng <Penny.Zheng@arm.com>
>> Cc: Bertrand Marquis <Bertrand.Marquis@arm.com>; Wei Chen
>> <Wei.Chen@arm.com>; nd <nd@arm.com>; xen-devel@lists.xenproject.org;
>> sstabellini@kernel.org; julien@xen.org
>> Subject: Re: [PATCH 07/10] xen/arm: intruduce alloc_domstatic_pages
>>
>> On 18.05.2021 07:21, Penny Zheng wrote:
>>> --- a/xen/common/page_alloc.c
>>> +++ b/xen/common/page_alloc.c
>>> @@ -2447,6 +2447,9 @@ int assign_pages(
>>>       {
>>>           ASSERT(page_get_owner(&pg[i]) == NULL);
>>>           page_set_owner(&pg[i], d);
>>> +        /* use page_set_reserved_owner to set its reserved domain owner.
>> */
>>> +        if ( (pg[i].count_info & PGC_reserved) )
>>> +            page_set_reserved_owner(&pg[i], d);
>>
>> Now this is puzzling: What's the point of setting two owner fields to the same
>> value? I also don't recall you having introduced
>> page_set_reserved_owner() for x86, so how is this going to build there?
>>
> 
> Thanks for pointing out that it will fail on x86.
> As for the same value, sure, I shall change it to domid_t domid to record its reserved owner.
> Only domid is enough for differentiate.
> And even when domain get rebooted, struct domain may be destroyed, but domid will stays
> The same.
> Major user cases for domain on static allocation are referring to the whole system are static,
> No runtime creation.

One may want to have static memory yet doesn't care about the domid. So 
I am not in favor to restrict about the domid unless there is no other way.

Cheers,

-- 
Julien Grall