Re: [PATCH v7 9/9] xen: retrieve reserved pages on populate_physmap

[Julien Grall <julien@xxxxxxx>]

Hi Penny,

On 20/06/2022 03:44, Penny Zheng wrote:
> When a static domain populates memory through populate_physmap at runtime,
> it shall retrieve reserved pages from resv_page_list to make sure that
> guest RAM is still restricted in statically configured memory regions.
> This commit also introduces a new helper acquire_reserved_page to make it work.
>
> Signed-off-by: Penny Zheng <penny.zheng@xxxxxxx>
> ---
> v7 changes:
> - remove the lock, since we add the page to rsv_page_list after it has
> been totally freed.
Hmmm... Adding the page after it has been totally freed doesn't mean you 
can get away with the lock. AFAICT you can still have concurrent 
free/allocate that could modify the list.
Therefore if you add/remove pages without the list, you would end up to 
corrupt the list.
If you disagree, then please point out which lock (or mechanism) will 
prevent concurrent access.
Cheers,

--
Julien Grall