[PATCH v12 27/29] HMM: fork copy migrated memory into system memory for child process.

Path	csiph.com!aioe.org!gothmog.csi.it!bofh.it!news.nic.it!robomod
From	Jérôme Glisse <jglisse@redhat.com>
Newsgroups	linux.kernel
Subject	[PATCH v12 27/29] HMM: fork copy migrated memory into system memory for child process.
Date	Tue, 08 Mar 2016 20:50:02 +0100
Message-ID	<ravNM-5ru-7@gated-at.bofh.it> (permalink)
References	<ravNL-5ru-3@gated-at.bofh.it>
MIME-Version	1.0
Content-Type	text/plain; charset=UTF-8
Content-Transfer-Encoding	8bit
X-Scanned-By	MIMEDefang 2.68 on 10.5.11.24
Sender	robomod@news.nic.it
List-ID	<linux-kernel.vger.kernel.org>
X-Mailing-List	linux-kernel@vger.kernel.org
Approved	robomod@news.nic.it
Lines	68
Organization	linux.* mail to news gateway
X-Original-Cc	Linus Torvalds <torvalds@linux-foundation.org>, <joro@8bytes.org>, Mel Gorman <mgorman@suse.de>, "H. Peter Anvin" <hpa@zytor.com>, Peter Zijlstra <peterz@infradead.org>, Andrea Arcangeli <aarcange@redhat.com>, Johannes Weiner <jweiner@redhat.com>, Larry Woodman <lwoodman@redhat.com>, Rik van Riel <riel@redhat.com>, Dave Airlie <airlied@redhat.com>, Brendan Conoboy <blc@redhat.com>, Joe Donohue <jdonohue@redhat.com>, Christophe Harle <charle@nvidia.com>, Duncan Poole <dpoole@nvidia.com>, Sherry Cheung <SCheung@nvidia.com>, Subhash Gutti <sgutti@nvidia.com>, John Hubbard <jhubbard@nvidia.com>, Mark Hairgrove <mhairgrove@nvidia.com>, Lucien Dunning <ldunning@nvidia.com>, Cameron Buschardt <cabuschardt@nvidia.com>, Arvind Gopalakrishnan <arvindg@nvidia.com>, Haggai Eran <haggaie@mellanox.com>, Shachar Raindel <raindel@mellanox.com>, Liran Liss <liranl@mellanox.com>, Roland Dreier <roland@purestorage.com>, Ben Sander <ben.sander@amd.com>, Greg Stoner <Greg.Stoner@amd.com>, John Bridgman <John.Bridgman@amd.com>, Michael Mantor <Michael.Mantor@amd.com>, Paul Blinzer <Paul.Blinzer@amd.com>, Leonid Shamis <Leonid.Shamis@amd.com>, Laurent Morichetti <Laurent.Morichetti@amd.com>, Alexander Deucher <Alexander.Deucher@amd.com>, Jérôme Glisse <jglisse@redhat.com>
X-Original-Date	Tue, 8 Mar 2016 15:43:20 -0500
X-Original-Message-ID	<1457469802-11850-28-git-send-email-jglisse@redhat.com>
X-Original-References	<1457469802-11850-1-git-send-email-jglisse@redhat.com>
X-Original-Sender	linux-kernel-owner@vger.kernel.org
Xref	csiph.com linux.kernel:1353336

Show key headers only | View raw

When forking if process being fork had any memory migrated to some
device memory, we need to make a system copy for the child process.
Latter patches can revisit this and use the same COW semantic for
device memory.

Signed-off-by: Jérôme Glisse <jglisse@redhat.com>
---
 mm/hmm.c | 38 +++++++++++++++++++++++++++++++++++++-
 1 file changed, 37 insertions(+), 1 deletion(-)

diff --git a/mm/hmm.c b/mm/hmm.c
index 435e376..4dcd98f 100644
--- a/mm/hmm.c
+++ b/mm/hmm.c
@@ -483,7 +483,37 @@ int hmm_mm_fork(struct mm_struct *src_mm,
 		unsigned long start,
 		unsigned long end)
 {
-	return -ENOMEM;
+	unsigned long npages = (end - start) >> PAGE_SHIFT;
+	struct hmm_event event;
+	dma_addr_t *dst;
+	struct hmm *hmm;
+	pte_t *new_pte;
+	int ret;
+
+	hmm = hmm_ref(src_mm->hmm);
+	if (!hmm)
+		return -EINVAL;
+
+
+	dst = kcalloc(npages, sizeof(*dst), GFP_KERNEL);
+	if (!dst) {
+		hmm_unref(hmm);
+		return -ENOMEM;
+	}
+	new_pte = kcalloc(npages, sizeof(*new_pte), GFP_KERNEL);
+	if (!new_pte) {
+		kfree(dst);
+		hmm_unref(hmm);
+		return -ENOMEM;
+	}
+
+	hmm_event_init(&event, hmm, start, end, HMM_FORK);
+	ret = hmm_migrate_back(hmm, &event, dst_mm, dst_vma, new_pte,
+			       dst, start, end);
+	hmm_unref(hmm);
+	kfree(new_pte);
+	kfree(dst);
+	return ret;
 }
 EXPORT_SYMBOL(hmm_mm_fork);
 
@@ -665,6 +695,12 @@ static void hmm_mirror_update_pte(struct hmm_mirror *mirror,
 	}
 
 	if (hmm_pte_test_valid_dev(hmm_pte)) {
+		/*
+		 * On fork device memory is duplicated so no need to write
+		 * protect it.
+		 */
+		if (event->etype == HMM_FORK)
+			return;
 		*hmm_pte &= event->pte_mask;
 		if (!hmm_pte_test_valid_dev(hmm_pte))
 			hmm_pt_iter_directory_unref(iter);
-- 
2.4.3

Back to linux.kernel | Previous | Next | Find similar | Unroll thread

Thread

[PATCH v12 27/29] HMM: fork copy migrated memory into system memory for child process. Jérôme Glisse <jglisse@redhat.com> - 2016-03-08 20:50 +0100

csiph-web