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



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



 


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