Re: [RFC PATCH v2 10/10] firmware: arm_scmi: Add virtio transport

From: Viresh Kumar <viresh.kumar@linaro.org>
To: Peter Hilber <peter.hilber@opensynergy.com>
Cc: Linux ARM <linux-arm-kernel@lists.infradead.org>,
	DTML <devicetree@vger.kernel.org>,
	virtualization@lists.linux-foundation.org,
	virtio-dev@lists.oasis-open.org,
	Igor Skalkin <igor.skalkin@opensynergy.com>,
	Rob Herring <robh+dt@kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Sudeep Holla <sudeep.holla@arm.com>,
	souvik.chakravarty@arm.com, alex.bennee@linaro.org,
	jean-philippe@linaro.org, mikhail.golubev@opensynergy.com,
	anton.yakovlev@opensynergy.com,
	"Michael S. Tsirkin" <mst@redhat.com>,
	Jason Wang <jasowang@redhat.com>,
	Vincent Guittot <vincent.guittot@linaro.org>
Subject: Re: [RFC PATCH v2 10/10] firmware: arm_scmi: Add virtio transport
Date: Thu, 8 Apr 2021 09:15:28 +0530	[thread overview]
Message-ID: <CAOh2x==6TH-A8076weSLy7kLqrNZgRgp2GFyAEGGPyikw1rgGg@mail.gmail.com> (raw)
In-Reply-To: <20201105212116.411422-11-peter.hilber@opensynergy.com>

On Fri, Nov 6, 2020 at 2:59 AM Peter Hilber
<peter.hilber@opensynergy.com> wrote:

> +static int scmi_vio_probe(struct virtio_device *vdev)
> +{
> +       struct device *dev = &vdev->dev;
> +       struct scmi_vio_channel **vioch;
> +       bool have_vq_rx;
> +       int vq_cnt;
> +       int i;
> +       struct virtqueue *vqs[VIRTIO_SCMI_VQ_MAX_CNT];
> +
> +       vioch = devm_kcalloc(dev, VIRTIO_SCMI_VQ_MAX_CNT, sizeof(*vioch),
> +                            GFP_KERNEL);
> +       if (!vioch)
> +               return -ENOMEM;
> +
> +       have_vq_rx = virtio_has_feature(vdev, VIRTIO_SCMI_F_P2A_CHANNELS);
> +       vq_cnt = have_vq_rx ? VIRTIO_SCMI_VQ_MAX_CNT : 1;
> +
> +       for (i = 0; i < vq_cnt; i++) {
> +               vioch[i] = devm_kzalloc(dev, sizeof(**vioch), GFP_KERNEL);
> +               if (!vioch[i])
> +                       return -ENOMEM;
> +       }
> +
> +       if (have_vq_rx)
> +               vioch[VIRTIO_SCMI_VQ_RX]->is_rx = true;
> +
> +       if (virtio_find_vqs(vdev, vq_cnt, vqs, scmi_vio_complete_callbacks,
> +                           scmi_vio_vqueue_names, NULL)) {
> +               dev_err(dev, "Failed to get %d virtqueue(s)\n", vq_cnt);
> +               return -1;
> +       }
> +       dev_info(dev, "Found %d virtqueue(s)\n", vq_cnt);
> +
> +       for (i = 0; i < vq_cnt; i++) {
> +               spin_lock_init(&vioch[i]->lock);
> +               vioch[i]->vqueue = vqs[i];
> +               vioch[i]->vqueue->priv = vioch[i];

The vqueue->priv field is used by core, you can't update it else
notifications won't work.

> +       }
> +
> +       vdev->priv = vioch;
> +
> +       virtio_device_ready(vdev);
> +
> +       return 0;
> +}

diff --git a/drivers/firmware/arm_scmi/virtio.c
b/drivers/firmware/arm_scmi/virtio.c
index f70aa72f34f1..b1af77341b30 100644
--- a/drivers/firmware/arm_scmi/virtio.c
+++ b/drivers/firmware/arm_scmi/virtio.c
@@ -80,7 +80,8 @@ static int scmi_vio_populate_vq_rx(struct
scmi_vio_channel *vioch,

 static void scmi_vio_complete_cb(struct virtqueue *vqueue)
 {
-       struct scmi_vio_channel *vioch = vqueue->priv;
+       struct scmi_vio_channel **_vioch = vqueue->vdev->priv;
+       struct scmi_vio_channel *vioch = _vioch[vqueue->index];
        unsigned long iflags;
        unsigned int length;

@@ -454,7 +455,6 @@ static int scmi_vio_probe(struct virtio_device *vdev)
        for (i = 0; i < vq_cnt; i++) {
                spin_lock_init(&vioch[i]->lock);
                vioch[i]->vqueue = vqs[i];
-               vioch[i]->vqueue->priv = vioch[i];
        }

        vdev->priv = vioch;
