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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 24223C19F2C for ; Tue, 2 Aug 2022 12:49:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236138AbiHBMtc (ORCPT ); Tue, 2 Aug 2022 08:49:32 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34876 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231797AbiHBMtb (ORCPT ); Tue, 2 Aug 2022 08:49:31 -0400 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 0FA9963BE; Tue, 2 Aug 2022 05:49:27 -0700 (PDT) Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 3E4BE13D5; Tue, 2 Aug 2022 05:49:28 -0700 (PDT) Received: from [10.1.35.143] (e121487-lin.cambridge.arm.com [10.1.35.143]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 5C2823F67D; Tue, 2 Aug 2022 05:49:24 -0700 (PDT) Message-ID: <7e64ce61-89b1-40aa-8295-00ca42b9a959@arm.com> Date: Tue, 2 Aug 2022 13:49:14 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.11.0 Subject: Re: [PATCH v2 4/4] hwrng: virtio - always add a pending request Content-Language: en-US To: Laurent Vivier , linux-kernel@vger.kernel.org Cc: amit@kernel.org, Herbert Xu , Matt Mackall , virtualization@lists.linux-foundation.org, Dmitriy Vyukov , rusty@rustcorp.com.au, akong@redhat.com, Alexander Potapenko , "Michael S . Tsirkin" , linux-crypto@vger.kernel.org, Mauricio De Carvalho , Kevin Brodsky , Vladimir Murzin References: <20211028101111.128049-1-lvivier@redhat.com> <20211028101111.128049-5-lvivier@redhat.com> From: Vladimir Murzin In-Reply-To: <20211028101111.128049-5-lvivier@redhat.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Laurent, On 10/28/21 11:11, Laurent Vivier wrote: > If we ensure we have already some data available by enqueuing > again the buffer once data are exhausted, we can return what we > have without waiting for the device answer. > > Signed-off-by: Laurent Vivier > --- > drivers/char/hw_random/virtio-rng.c | 26 ++++++++++++-------------- > 1 file changed, 12 insertions(+), 14 deletions(-) > > diff --git a/drivers/char/hw_random/virtio-rng.c b/drivers/char/hw_random/virtio-rng.c > index 8ba97cf4ca8f..0a7dde135db1 100644 > --- a/drivers/char/hw_random/virtio-rng.c > +++ b/drivers/char/hw_random/virtio-rng.c > @@ -20,7 +20,6 @@ struct virtrng_info { > struct virtqueue *vq; > char name[25]; > int index; > - bool busy; > bool hwrng_register_done; > bool hwrng_removed; > /* data transfer */ > @@ -44,16 +43,18 @@ static void random_recv_done(struct virtqueue *vq) > return; > > vi->data_idx = 0; > - vi->busy = false; > > complete(&vi->have_data); > } > > -/* The host will fill any buffer we give it with sweet, sweet randomness. */ > -static void register_buffer(struct virtrng_info *vi) > +static void request_entropy(struct virtrng_info *vi) > { > struct scatterlist sg; > > + reinit_completion(&vi->have_data); > + vi->data_avail = 0; > + vi->data_idx = 0; > + > sg_init_one(&sg, vi->data, sizeof(vi->data)); > > /* There should always be room for one buffer. */ > @@ -69,6 +70,8 @@ static unsigned int copy_data(struct virtrng_info *vi, void *buf, > memcpy(buf, vi->data + vi->data_idx, size); > vi->data_idx += size; > vi->data_avail -= size; > + if (vi->data_avail == 0) > + request_entropy(vi); > return size; > } > > @@ -98,13 +101,7 @@ static int virtio_read(struct hwrng *rng, void *buf, size_t size, bool wait) > * so either size is 0 or data_avail is 0 > */ > while (size != 0) { > - /* data_avail is 0 */ > - if (!vi->busy) { > - /* no pending request, ask for more */ > - vi->busy = true; > - reinit_completion(&vi->have_data); > - register_buffer(vi); > - } > + /* data_avail is 0 but a request is pending */ > ret = wait_for_completion_killable(&vi->have_data); > if (ret < 0) > return ret; > @@ -126,8 +123,7 @@ static void virtio_cleanup(struct hwrng *rng) > { > struct virtrng_info *vi = (struct virtrng_info *)rng->priv; > > - if (vi->busy) > - complete(&vi->have_data); > + complete(&vi->have_data); > } > > static int probe_common(struct virtio_device *vdev) > @@ -163,6 +159,9 @@ static int probe_common(struct virtio_device *vdev) > goto err_find; > } > > + /* we always have a pending entropy request */ > + request_entropy(vi); > + > return 0; > > err_find: > @@ -181,7 +180,6 @@ static void remove_common(struct virtio_device *vdev) > vi->data_idx = 0; > complete(&vi->have_data); > vdev->config->reset(vdev); > - vi->busy = false; > if (vi->hwrng_register_done) > hwrng_unregister(&vi->hwrng); > vdev->config->del_vqs(vdev); We observed that after this commit virtio-rng implementation in FVP doesn't work INFO: bp.virtio_rng: Selected Random Generator Device: XORSHIFT DEVICE INFO: bp.virtio_rng: Using seed value: 0x5674bba8 Error: FVP_Base_AEMvA: bp.virtio_rng: Found invalid descriptor index In file: (unknown):0 In process: FVP_Base_AEMvA.thread_p_12 @ 935500020 ns Info: FVP_Base_AEMvA: bp.virtio_rng: Could not extract buffer while basic baremetal test works as expected INFO: bp.virtio_rng: Selected Random Generator Device: XORSHIFT DEVICE INFO: bp.virtio_rng: Using seed value: 0x541c142e Info: FVP_Base_AEMv8A: bp.virtio_rng: Generated Number: 0x4b098991ceb377e6 Info: FVP_Base_AEMv8A: bp.virtio_rng: Generated Number: 0xbdcbe3f765ba62f7 We are trying to get an idea what is missing and where, yet none of us familiar with the driver :( I'm looping Kevin who originally reported that and Mauricio who is looking form the FVP side. Cheers Vladimir