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[88.21.202.17]) by smtp.gmail.com with ESMTPSA id e21sm15205392wme.34.2020.05.18.02.18.55 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 18 May 2020 02:18:56 -0700 (PDT) Subject: Re: [PATCH v1 1/3] virtio-balloon: fix free page hinting without an iothread To: David Hildenbrand , qemu-devel@nongnu.org References: <20200518083704.52646-1-david@redhat.com> <20200518083704.52646-2-david@redhat.com> From: =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= Message-ID: <45026d92-04e9-b654-f05a-3996fd9fa09d@redhat.com> Date: Mon, 18 May 2020 11:18:55 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 MIME-Version: 1.0 In-Reply-To: <20200518083704.52646-2-david@redhat.com> Content-Language: en-US X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=207.211.31.81; envelope-from=philmd@redhat.com; helo=us-smtp-delivery-1.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/05/17 22:52:27 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H2=-0.001, SPF_PASS=-0.001, URIBL_BLOCKED=0.001 autolearn=_AUTOLEARN X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Alexander Bulekov , Wei Wang , Alexander Duyck , "Michael S . Tsirkin" Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 5/18/20 10:37 AM, David Hildenbrand wrote: > In case we don't have an iothread, we mark the feature as abscent but > still add the queue. 'free_page_bh' remains set to NULL. > > qemu-system-i386 \ > -M microvm \ > -nographic \ > -device virtio-balloon-device,free-page-hint=true \ > -nographic \ > -display none \ > -monitor none \ > -serial none \ > -qtest stdio > > Doing a "write 0xc0000e30 0x24 > 0x030000000300000003000000030000000300000003000000030000000300000003000000" > > We will trigger a SEGFAULT. Let's move the check and bail out. > > While at it, move the static initializations to instance_initialize(). > > Fixes: c13c4153f76d ("virtio-balloon: VIRTIO_BALLOON_F_FREE_PAGE_HINT") > Reported-by: Alexander Bulekov > Cc: Wei Wang > Cc: Michael S. Tsirkin > Cc: Philippe Mathieu-Daudé > Cc: Alexander Duyck > Signed-off-by: David Hildenbrand > --- > hw/virtio/virtio-balloon.c | 35 ++++++++++++++++++----------------- > 1 file changed, 18 insertions(+), 17 deletions(-) > > diff --git a/hw/virtio/virtio-balloon.c b/hw/virtio/virtio-balloon.c > index 065cd450f1..dc3b1067ab 100644 > --- a/hw/virtio/virtio-balloon.c > +++ b/hw/virtio/virtio-balloon.c > @@ -789,6 +789,13 @@ static void virtio_balloon_device_realize(DeviceState *dev, Error **errp) > return; > } > > + if (virtio_has_feature(s->host_features, > + VIRTIO_BALLOON_F_FREE_PAGE_HINT) && !s->iothread) { > + error_setg(errp, "'free-page-hint' requires 'iothread' to be set"); > + virtio_cleanup(vdev); > + return; This is exactly what I had in mind! > + } > + > s->ivq = virtio_add_queue(vdev, 128, virtio_balloon_handle_output); > s->dvq = virtio_add_queue(vdev, 128, virtio_balloon_handle_output); > s->svq = virtio_add_queue(vdev, 128, virtio_balloon_receive_stats); > @@ -797,24 +804,11 @@ static void virtio_balloon_device_realize(DeviceState *dev, Error **errp) > VIRTIO_BALLOON_F_FREE_PAGE_HINT)) { > s->free_page_vq = virtio_add_queue(vdev, VIRTQUEUE_MAX_SIZE, > virtio_balloon_handle_free_page_vq); > - s->free_page_report_status = FREE_PAGE_REPORT_S_STOP; > - s->free_page_report_cmd_id = > - VIRTIO_BALLOON_FREE_PAGE_REPORT_CMD_ID_MIN; > - s->free_page_report_notify.notify = > - virtio_balloon_free_page_report_notify; > precopy_add_notifier(&s->free_page_report_notify); > - if (s->iothread) { > - object_ref(OBJECT(s->iothread)); > - s->free_page_bh = aio_bh_new(iothread_get_aio_context(s->iothread), > - virtio_ballloon_get_free_page_hints, s); > - qemu_mutex_init(&s->free_page_lock); > - qemu_cond_init(&s->free_page_cond); > - s->block_iothread = false; > - } else { > - /* Simply disable this feature if the iothread wasn't created. */ > - s->host_features &= ~(1 << VIRTIO_BALLOON_F_FREE_PAGE_HINT); > - virtio_error(vdev, "iothread is missing"); > - } > + > + object_ref(OBJECT(s->iothread)); > + s->free_page_bh = aio_bh_new(iothread_get_aio_context(s->iothread), > + virtio_ballloon_get_free_page_hints, s); > } > reset_stats(s); > } > @@ -892,6 +886,13 @@ static void virtio_balloon_instance_init(Object *obj) > { > VirtIOBalloon *s = VIRTIO_BALLOON(obj); > > + qemu_mutex_init(&s->free_page_lock); > + qemu_cond_init(&s->free_page_cond); > + s->free_page_report_status = FREE_PAGE_REPORT_S_STOP; > + s->free_page_report_cmd_id = VIRTIO_BALLOON_FREE_PAGE_REPORT_CMD_ID_MIN; > + s->free_page_report_notify.notify = virtio_balloon_free_page_report_notify; > + s->block_iothread = false; This part is even cleaner. Reviewed-by: Philippe Mathieu-Daudé > + > object_property_add(obj, "guest-stats", "guest statistics", > balloon_stats_get_all, NULL, NULL, s); > >