On 10/12/2017 02:27 PM, Anthony Yznaga wrote:
On Oct 12, 2017, at 7:44 AM, Khalid Aziz <khalid.a...@oracle.com> wrote:
On 10/06/2017 04:12 PM, Anthony Yznaga wrote:
On Sep 25, 2017, at 9:49 AM, Khalid Aziz <khalid.a...@oracle.com> wrote:
This patch extends mprotect to enable ADI (TSTATE.mcde), enable/disable
MCD (Memory Corruption Detection) on selected memory ranges, enable
TTE.mcd in PTEs, return ADI parameters to userspace and save/restore ADI
version tags on page swap out/in or migration. ADI is not enabled by
I still don't believe migration is properly supported. Your
implementation is relying on a fault happening on a page while its
migration is in progress so that do_swap_page() will be called, but
I don't see how do_swap_page() will be called if a fault does not
happen until after the migration has completed.
User pages are on LRU list and for the mapped pages on LRU list,
migrate_pages() ultimately calls try_to_unmap_one and makes a migration swap
entry for the page being migrated. This forces a page fault upon access on the
destination node and the page is swapped back in from swap cache. The fault is
forced by the migration swap entry, rather than fault being an accidental
event. If page fault happens on the destination node while migration is in
progress, do_swap_page() waits until migration is done. Please take a look at
the code in __unmap_and_move().
I looked at the code again, and I now believe ADI tags are never restored for
migrated pages. Here's why:
I will take a look at it again. I have run extensive tests migrating
pages of a process across multiple NUMA nodes over and over again and
ADI tags were never lost, so this does work. I won't rule out the
possibility of having missed a code path where tags are not restored and
I will look for it.
Thanks,
Khalid
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