From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 63C23C4CEC4 for ; Thu, 19 Sep 2019 14:23:13 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 2262F20882 for ; Thu, 19 Sep 2019 14:23:13 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 2262F20882 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id A3C116B0366; Thu, 19 Sep 2019 10:23:12 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 9EA056B0367; Thu, 19 Sep 2019 10:23:12 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 8D99B6B0368; Thu, 19 Sep 2019 10:23:12 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0142.hostedemail.com [216.40.44.142]) by kanga.kvack.org (Postfix) with ESMTP id 656A36B0366 for ; Thu, 19 Sep 2019 10:23:12 -0400 (EDT) Received: from smtpin17.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with SMTP id 06F96824376A for ; Thu, 19 Sep 2019 14:23:12 +0000 (UTC) X-FDA: 75951887424.17.baby66_9048a7235664b X-HE-Tag: baby66_9048a7235664b X-Filterd-Recvd-Size: 7234 Received: from mx1.redhat.com (mx1.redhat.com [209.132.183.28]) by imf12.hostedemail.com (Postfix) with ESMTP for ; Thu, 19 Sep 2019 14:23:11 +0000 (UTC) Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 49DE52A09A0; Thu, 19 Sep 2019 14:23:10 +0000 (UTC) Received: from t460s.redhat.com (unknown [10.36.118.9]) by smtp.corp.redhat.com (Postfix) with ESMTP id 497C960872; Thu, 19 Sep 2019 14:23:02 +0000 (UTC) From: David Hildenbrand To: linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, virtualization@lists.linux-foundation.org, Andrea Arcangeli , David Hildenbrand , "Michael S. Tsirkin" , Jason Wang , Oscar Salvador , Michal Hocko , Igor Mammedov , Dave Young , Andrew Morton , Dan Williams , Pavel Tatashin , Stefan Hajnoczi , Vlastimil Babka Subject: [PATCH RFC v3 3/9] virtio-mem: Paravirtualized memory hotunplug part 1 Date: Thu, 19 Sep 2019 16:22:22 +0200 Message-Id: <20190919142228.5483-4-david@redhat.com> In-Reply-To: <20190919142228.5483-1-david@redhat.com> References: <20190919142228.5483-1-david@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.38]); Thu, 19 Sep 2019 14:23:10 +0000 (UTC) Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Unplugging subblocks of memory blocks that are offline is easy. All we have to do is watch out for concurrent onlining acticity. Cc: "Michael S. Tsirkin" Cc: Jason Wang Cc: Oscar Salvador Cc: Michal Hocko Cc: Igor Mammedov Cc: Dave Young Cc: Andrew Morton Cc: Dan Williams Cc: Pavel Tatashin Cc: Stefan Hajnoczi Cc: Vlastimil Babka Signed-off-by: David Hildenbrand --- drivers/virtio/virtio_mem.c | 109 +++++++++++++++++++++++++++++++++++- 1 file changed, 107 insertions(+), 2 deletions(-) diff --git a/drivers/virtio/virtio_mem.c b/drivers/virtio/virtio_mem.c index 597fab4933f6..6fb55d4b6f6c 100644 --- a/drivers/virtio/virtio_mem.c +++ b/drivers/virtio/virtio_mem.c @@ -119,7 +119,7 @@ struct virtio_mem { * * When this lock is held the pointers can't change, ONLINE and * OFFLINE blocks can't change the state and no subblocks will get - * plugged. + * plugged/unplugged. */ struct mutex hotplug_mutex; bool hotplug_active; @@ -322,6 +322,19 @@ static bool virtio_mem_mb_test_sb_plugged(struct vir= tio_mem *vm, bit + count; } =20 +/* + * Test if all selected subblocks are unplugged. + */ +static bool virtio_mem_mb_test_sb_unplugged(struct virtio_mem *vm, + unsigned long mb_id, int sb_id, + int count) +{ + const int bit =3D (mb_id - vm->first_mb_id) * vm->nb_sb_per_mb + sb_id; + + /* TODO: Helper similar to bitmap_set() */ + return find_next_bit(vm->sb_bitmap, bit + count, bit) >=3D bit + count; +} + /* * Find the first plugged subblock. Returns vm->nb_sb_per_mb in case the= re is * none. @@ -512,6 +525,9 @@ static void virtio_mem_notify_offline(struct virtio_m= em *vm, BUG(); break; } + + /* trigger the workqueue, maybe we can now unplug memory. */ + virtio_mem_retry(vm); } =20 static void virtio_mem_notify_online(struct virtio_mem *vm, unsigned lon= g mb_id, @@ -1129,6 +1145,93 @@ static int virtio_mem_plug_request(struct virtio_m= em *vm, uint64_t diff) return rc; } =20 +/* + * Unplug the desired number of plugged subblocks of an offline memory b= lock. + * Will fail if any subblock cannot get unplugged (instead of skipping i= t). + * + * Will modify the state of the memory block. Might temporarily drop the + * hotplug_mutex. + * + * Note: Can fail after some subblocks were successfully unplugged. + */ +static int virtio_mem_mb_unplug_any_sb_offline(struct virtio_mem *vm, + unsigned long mb_id, + uint64_t *nb_sb) +{ + int rc; + + rc =3D virtio_mem_mb_unplug_any_sb(vm, mb_id, nb_sb); + + /* some subblocks might have been unplugged even on failure */ + if (!virtio_mem_mb_test_sb_plugged(vm, mb_id, 0, vm->nb_sb_per_mb)) + virtio_mem_mb_set_state(vm, mb_id, + VIRTIO_MEM_MB_STATE_OFFLINE_PARTIAL); + if (rc) + return rc; + + if (virtio_mem_mb_test_sb_unplugged(vm, mb_id, 0, vm->nb_sb_per_mb)) { + /* + * Remove the block from Linux - this should never fail. + * Hinder the block from getting onlined by marking it + * unplugged. Temporarily drop the mutex, so + * any pending GOING_ONLINE requests can be serviced/rejected. + */ + virtio_mem_mb_set_state(vm, mb_id, + VIRTIO_MEM_MB_STATE_UNUSED); + + mutex_unlock(&vm->hotplug_mutex); + rc =3D virtio_mem_mb_remove(vm, mb_id); + BUG_ON(rc); + mutex_lock(&vm->hotplug_mutex); + } + return 0; +} + +/* + * Try to unplug the requested amount of memory. + */ +static int virtio_mem_unplug_request(struct virtio_mem *vm, uint64_t dif= f) +{ + uint64_t nb_sb =3D diff / vm->subblock_size; + unsigned long mb_id; + int rc; + + if (!nb_sb) + return 0; + + /* + * We'll drop the mutex a couple of times when it is safe to do so. + * This might result in some blocks switching the state (online/offline= ) + * and we could miss them in this run - we will retry again later. + */ + mutex_lock(&vm->hotplug_mutex); + + /* Try to unplug subblocks of partially plugged offline blocks. */ + virtio_mem_for_each_mb_state(vm, mb_id, + VIRTIO_MEM_MB_STATE_OFFLINE_PARTIAL) { + rc =3D virtio_mem_mb_unplug_any_sb_offline(vm, mb_id, + &nb_sb); + if (rc || !nb_sb) + goto out_unlock; + cond_resched(); + } + + /* Try to unplug subblocks of plugged offline blocks. */ + virtio_mem_for_each_mb_state(vm, mb_id, VIRTIO_MEM_MB_STATE_OFFLINE) { + rc =3D virtio_mem_mb_unplug_any_sb_offline(vm, mb_id, + &nb_sb); + if (rc || !nb_sb) + goto out_unlock; + cond_resched(); + } + + mutex_unlock(&vm->hotplug_mutex); + return 0; +out_unlock: + mutex_unlock(&vm->hotplug_mutex); + return rc; +} + /* * Try to unplug all blocks that couldn't be unplugged before, for examp= le, * because the hypervisor was busy. @@ -1209,8 +1312,10 @@ static void virtio_mem_run_wq(struct work_struct *= work) if (vm->requested_size > vm->plugged_size) { diff =3D vm->requested_size - vm->plugged_size; rc =3D virtio_mem_plug_request(vm, diff); + } else { + diff =3D vm->plugged_size - vm->requested_size; + rc =3D virtio_mem_unplug_request(vm, diff); } - /* TODO: try to unplug memory */ } =20 switch (rc) { --=20 2.21.0