On 5/15/20 4:15 PM, Jason Gunthorpe wrote:
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@xxxxxxxxxx> 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
For some reason I had looked at that and rejected it but of course, it works fine. :-) Thanks!
