[Xen-devel] [PATCH] mem_sharing: fix race condition of nominate and unshare

[Jui-Hao Chiang <juihaochiang@xxxxxxxxx>]

Hi, this patch does the following
(1) When updating/checking p2m type for mem_sharing, we must hold shr_lock
(2) For nominate operation, if the page is already nominated, return the handle from page_info->shr_handle
(3) For unshare operation, it is possible that multiple users unshare a page via hvm_hap_nested_page_fault() at the same time. If the page is already un-shared by someone else, simply return success.

NOTE: we assume that nobody holds page_alloc_lock/p2m_lock before calling nominate/share/unshare.

Signed-off-by: Jui-Hao Chiang <juihaochiang@xxxxxxxxx>
Signed-off-by: Han-Lin Li <Han-Lin.Li@xxxxxxxxxxx>

Bests,
Jui-Hao

Attachment: mem_sharing_p2mt_race.patch
Description: Text Data

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