From: Stefan Hajnoczi Date: Tue, 6 Feb 2024 19:06:07 +0000 (-0500) Subject: virtio-blk: clarify that there is at least 1 virtqueue X-Git-Tag: qemu-xen-4.20.0~306^2~14 X-Git-Url: http://xenbits.xensource.com/gitweb?a=commitdiff_plain;h=5fbcbd50fca67ffe35317f2e86f6822aa22e41c6;p=qemu-xen.git virtio-blk: clarify that there is at least 1 virtqueue It is not possible to instantiate a virtio-blk device with 0 virtqueues. The following check is located in ->realize(): if (!conf->num_queues) { error_setg(errp, "num-queues property must be larger than 0"); return; } Later on we access s->vq_aio_context[0] under the assumption that there is as least one virtqueue. Hanna Czenczek noted that it would help to show that the array index is already valid. Add an assertion to document that s->vq_aio_context[0] is always safe...and catch future code changes that break this assumption. Suggested-by: Hanna Czenczek Reviewed-by: Manos Pitsidianakis Reviewed-by: Hanna Czenczek Signed-off-by: Stefan Hajnoczi Message-ID: <20240206190610.107963-3-stefanha@redhat.com> Reviewed-by: Kevin Wolf Reviewed-by: Michael S. Tsirkin Signed-off-by: Kevin Wolf --- diff --git a/hw/block/virtio-blk.c b/hw/block/virtio-blk.c index 6e3e3a23ee..e430ba583c 100644 --- a/hw/block/virtio-blk.c +++ b/hw/block/virtio-blk.c @@ -1824,6 +1824,7 @@ static int virtio_blk_start_ioeventfd(VirtIODevice *vdev) * Try to change the AioContext so that block jobs and other operations can * co-locate their activity in the same AioContext. If it fails, nevermind. */ + assert(nvqs > 0); /* enforced during ->realize() */ r = blk_set_aio_context(s->conf.conf.blk, s->vq_aio_context[0], &local_err); if (r < 0) {