On Wed, May 13, 2020 at 02:45:07PM -0700, Ralph Campbell wrote:
The test driver uses an xa_array to store virtual to physical address translations for a simulated hardware device. The MMU notifier invalidation callback is used to keep the table consistent with the CPU page table and is frequently called only for a page or two. However, if the test process exits unexpectedly or is killed, the range can be [0..ULONG_MAX] in which case calling xa_erase() for every possible PFN results in CPU timeouts. Munmap() can result in a large range being invalidated but in that case, the xa_array is likely to contain entries that need to be invalidated. Check for [0..ULONG_MAX] explicitly and just destroy the whole table.
Signed-off-by: Ralph Campbell rcampbell@nvidia.com
This patch is based on Jason Gunthorpe's hmm tree and should be folded into the ("mm/hmm/test: add selftest driver for HMM") patch once this patch is reviewed, etc.
lib/test_hmm.c | 6 ++++++ 1 file changed, 6 insertions(+)
diff --git a/lib/test_hmm.c b/lib/test_hmm.c index 8b36c26b717b..b89852ec3c29 100644 +++ b/lib/test_hmm.c @@ -201,7 +201,13 @@ static void dmirror_do_update(struct dmirror *dmirror, unsigned long start, * The XArray doesn't hold references to pages since it relies on * the mmu notifier to clear page pointers when they become stale. * Therefore, it is OK to just clear the entry.
* However, if the entire address space is being invalidated, it* takes too long to clear them one at a time so destroy the array.- if (start == 0 && end == ULONG_MAX) {
xa_destroy(&dmirror->pt);return;- } for (pfn = start >> PAGE_SHIFT; pfn < (end >> PAGE_SHIFT); pfn++) xa_erase(&dmirror->pt, pfn);
}
Just use xa_for_each_range() instead of the naive loop, it already optimizes against membership and avoids the need for the xa_destroy hack
Jason