Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756264AbbEUUX4 (ORCPT ); Thu, 21 May 2015 16:23:56 -0400 Received: from mx1.redhat.com ([209.132.183.28]:47534 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755792AbbEUUXu (ORCPT ); Thu, 21 May 2015 16:23:50 -0400 From: jglisse@redhat.com To: akpm@linux-foundation.org Cc: , linux-mm@kvack.org, Linus Torvalds , , Mel Gorman , "H. Peter Anvin" , Peter Zijlstra , Andrea Arcangeli , Johannes Weiner , Larry Woodman , Rik van Riel , Dave Airlie , Brendan Conoboy , Joe Donohue , Duncan Poole , Sherry Cheung , Subhash Gutti , John Hubbard , Mark Hairgrove , Lucien Dunning , Cameron Buschardt , Arvind Gopalakrishnan , Haggai Eran , Shachar Raindel , Liran Liss , Roland Dreier , Ben Sander , Greg Stoner , John Bridgman , Michael Mantor , Paul Blinzer , Laurent Morichetti , Alexander Deucher , Oded Gabbay , =?UTF-8?q?J=C3=A9r=C3=B4me=20Glisse?= Subject: [PATCH 27/36] HMM: CPU page fault on migrated memory. Date: Thu, 21 May 2015 16:23:03 -0400 Message-Id: <1432239792-5002-8-git-send-email-jglisse@redhat.com> In-Reply-To: <1432239792-5002-1-git-send-email-jglisse@redhat.com> References: <1432236705-4209-1-git-send-email-j.glisse@gmail.com> <1432239792-5002-1-git-send-email-jglisse@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2328 Lines: 84 From: Jérôme Glisse When CPU try to access memory that have been migrated to device memory we have to copy it back to system memory. This patch implement the CPU page fault handler for special HMM pte swap entry. Signed-off-by: Jérôme Glisse --- mm/hmm.c | 54 +++++++++++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 53 insertions(+), 1 deletion(-) diff --git a/mm/hmm.c b/mm/hmm.c index 143c6ab..1a7554d 100644 --- a/mm/hmm.c +++ b/mm/hmm.c @@ -476,7 +476,59 @@ int hmm_handle_cpu_fault(struct mm_struct *mm, pmd_t *pmdp, unsigned long addr, unsigned flags, pte_t orig_pte) { - return VM_FAULT_SIGBUS; + unsigned long start, end; + struct hmm_event event; + swp_entry_t entry; + struct hmm *hmm; + dma_addr_t dst; + pte_t new_pte; + int ret; + + /* First check for poisonous entry. */ + entry = pte_to_swp_entry(orig_pte); + if (is_hmm_entry_poisonous(entry)) + return VM_FAULT_SIGBUS; + + hmm = hmm_ref(mm->hmm); + if (!hmm) { + pte_t poison = swp_entry_to_pte(make_hmm_entry_poisonous()); + spinlock_t *ptl; + pte_t *ptep; + + /* Check if cpu pte is already updated. */ + ptep = pte_offset_map_lock(mm, pmdp, addr, &ptl); + if (!pte_same(*ptep, orig_pte)) { + pte_unmap_unlock(ptep, ptl); + return 0; + } + set_pte_at(mm, addr, ptep, poison); + pte_unmap_unlock(ptep, ptl); + return VM_FAULT_SIGBUS; + } + + /* + * TODO we likely want to migrate more then one page at a time, we need + * to call into the device driver to get good hint on the range to copy + * back to system memory. + * + * For now just live with the one page at a time solution. + */ + start = addr & PAGE_MASK; + end = start + PAGE_SIZE; + hmm_event_init(&event, hmm, start, end, HMM_COPY_FROM_DEVICE); + + ret = hmm_migrate_back(hmm, &event, mm, vma, &new_pte, + &dst, start, end); + hmm_unref(hmm); + switch (ret) { + case 0: + return VM_FAULT_MAJOR; + case -ENOMEM: + return VM_FAULT_OOM; + case -EINVAL: + default: + return VM_FAULT_SIGBUS; + } } EXPORT_SYMBOL(hmm_handle_cpu_fault); -- 1.9.3 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/