From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: virtio-dev-return-6500-cohuck=redhat.com@lists.oasis-open.org Sender: List-Post: List-Help: List-Unsubscribe: List-Subscribe: Received: from lists.oasis-open.org (oasis-open.org [10.110.1.242]) by lists.oasis-open.org (Postfix) with ESMTP id A3FFA985DFA for ; Thu, 12 Dec 2019 17:12:28 +0000 (UTC) From: David Hildenbrand Date: Thu, 12 Dec 2019 18:11:27 +0100 Message-Id: <20191212171137.13872-4-david@redhat.com> In-Reply-To: <20191212171137.13872-1-david@redhat.com> References: <20191212171137.13872-1-david@redhat.com> MIME-Version: 1.0 Subject: [virtio-dev] [PATCH RFC v4 03/13] virtio-mem: Paravirtualized memory hotunplug part 1 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable To: linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, virtio-dev@lists.oasis-open.org, virtualization@lists.linux-foundation.org, kvm@vger.kernel.org, Michal Hocko , Andrew Morton , "Michael S . Tsirkin" , David Hildenbrand , Jason Wang , Oscar Salvador , Igor Mammedov , Dave Young , Dan Williams , Pavel Tatashin , Stefan Hajnoczi , Vlastimil Babka 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 8f4ceeab3d7c..f1af05def5df 100644 --- a/drivers/virtio/virtio_mem.c +++ b/drivers/virtio/virtio_mem.c @@ -119,7 +119,7 @@ struct virtio_mem { =09 * =09 * When this lock is held the pointers can't change, ONLINE and =09 * OFFLINE blocks can't change the state and no subblocks will get -=09 * plugged. +=09 * plugged/unplugged. =09 */ =09struct mutex hotplug_mutex; =09bool hotplug_active; @@ -321,6 +321,19 @@ static bool virtio_mem_mb_test_sb_plugged(struct virti= o_mem *vm, =09 bit + count; } =20 +/* + * Test if all selected subblocks are unplugged. + */ +static bool virtio_mem_mb_test_sb_unplugged(struct virtio_mem *vm, +=09=09=09=09=09 unsigned long mb_id, int sb_id, +=09=09=09=09=09 int count) +{ +=09const int bit =3D (mb_id - vm->first_mb_id) * vm->nb_sb_per_mb + sb_id; + +=09/* TODO: Helper similar to bitmap_set() */ +=09return 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 there= is * none. @@ -511,6 +524,9 @@ static void virtio_mem_notify_offline(struct virtio_mem= *vm, =09=09BUG(); =09=09break; =09} + +=09/* trigger the workqueue, maybe we can now unplug memory. */ +=09virtio_mem_retry(vm); } =20 static void virtio_mem_notify_online(struct virtio_mem *vm, unsigned long = mb_id, @@ -1123,6 +1139,93 @@ static int virtio_mem_plug_request(struct virtio_mem= *vm, uint64_t diff) =09return rc; } =20 +/* + * Unplug the desired number of plugged subblocks of an offline memory blo= ck. + * Will fail if any subblock cannot get unplugged (instead of skipping it)= . + * + * 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, +=09=09=09=09=09 unsigned long mb_id, +=09=09=09=09=09 uint64_t *nb_sb) +{ +=09int rc; + +=09rc =3D virtio_mem_mb_unplug_any_sb(vm, mb_id, nb_sb); + +=09/* some subblocks might have been unplugged even on failure */ +=09if (!virtio_mem_mb_test_sb_plugged(vm, mb_id, 0, vm->nb_sb_per_mb)) +=09=09virtio_mem_mb_set_state(vm, mb_id, +=09=09=09=09=09VIRTIO_MEM_MB_STATE_OFFLINE_PARTIAL); +=09if (rc) +=09=09return rc; + +=09if (virtio_mem_mb_test_sb_unplugged(vm, mb_id, 0, vm->nb_sb_per_mb)) { +=09=09/* +=09=09 * Remove the block from Linux - this should never fail. +=09=09 * Hinder the block from getting onlined by marking it +=09=09 * unplugged. Temporarily drop the mutex, so +=09=09 * any pending GOING_ONLINE requests can be serviced/rejected. +=09=09 */ +=09=09virtio_mem_mb_set_state(vm, mb_id, +=09=09=09=09=09VIRTIO_MEM_MB_STATE_UNUSED); + +=09=09mutex_unlock(&vm->hotplug_mutex); +=09=09rc =3D virtio_mem_mb_remove(vm, mb_id); +=09=09BUG_ON(rc); +=09=09mutex_lock(&vm->hotplug_mutex); +=09} +=09return 0; +} + +/* + * Try to unplug the requested amount of memory. + */ +static int virtio_mem_unplug_request(struct virtio_mem *vm, uint64_t diff) +{ +=09uint64_t nb_sb =3D diff / vm->subblock_size; +=09unsigned long mb_id; +=09int rc; + +=09if (!nb_sb) +=09=09return 0; + +=09/* +=09 * We'll drop the mutex a couple of times when it is safe to do so. +=09 * This might result in some blocks switching the state (online/offline= ) +=09 * and we could miss them in this run - we will retry again later. +=09 */ +=09mutex_lock(&vm->hotplug_mutex); + +=09/* Try to unplug subblocks of partially plugged offline blocks. */ +=09virtio_mem_for_each_mb_state(vm, mb_id, +=09=09=09=09 VIRTIO_MEM_MB_STATE_OFFLINE_PARTIAL) { +=09=09rc =3D virtio_mem_mb_unplug_any_sb_offline(vm, mb_id, +=09=09=09=09=09=09=09 &nb_sb); +=09=09if (rc || !nb_sb) +=09=09=09goto out_unlock; +=09=09cond_resched(); +=09} + +=09/* Try to unplug subblocks of plugged offline blocks. */ +=09virtio_mem_for_each_mb_state(vm, mb_id, VIRTIO_MEM_MB_STATE_OFFLINE) { +=09=09rc =3D virtio_mem_mb_unplug_any_sb_offline(vm, mb_id, +=09=09=09=09=09=09=09 &nb_sb); +=09=09if (rc || !nb_sb) +=09=09=09goto out_unlock; +=09=09cond_resched(); +=09} + +=09mutex_unlock(&vm->hotplug_mutex); +=09return 0; +out_unlock: +=09mutex_unlock(&vm->hotplug_mutex); +=09return rc; +} + /* * Try to unplug all blocks that couldn't be unplugged before, for example= , * because the hypervisor was busy. @@ -1203,8 +1306,10 @@ static void virtio_mem_run_wq(struct work_struct *wo= rk) =09=09if (vm->requested_size > vm->plugged_size) { =09=09=09diff =3D vm->requested_size - vm->plugged_size; =09=09=09rc =3D virtio_mem_plug_request(vm, diff); +=09=09} else { +=09=09=09diff =3D vm->plugged_size - vm->requested_size; +=09=09=09rc =3D virtio_mem_unplug_request(vm, diff); =09=09} -=09=09/* TODO: try to unplug memory */ =09} =20 =09switch (rc) { --=20 2.23.0 --------------------------------------------------------------------- To unsubscribe, e-mail: virtio-dev-unsubscribe@lists.oasis-open.org For additional commands, e-mail: virtio-dev-help@lists.oasis-open.org