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Re: [PATCH v3 1/4] vhost-user-rng: Add vhost-user-rng implementation


From: Mathieu Poirier
Subject: Re: [PATCH v3 1/4] vhost-user-rng: Add vhost-user-rng implementation
Date: Thu, 22 Jul 2021 10:44:55 -0600

Hi Alex,

On Wed, Jul 21, 2021 at 09:52:50AM +0100, Alex Bennée wrote:
> 
> Mathieu Poirier <mathieu.poirier@linaro.org> writes:
> 
> > Following in the footsteps of what whas done for vhost-user-i2c
> > and virtiofsd, introduce a random number generator (RNG) backend
> > that communicates with a vhost-user server to retrieve entropy.
> > That way another VMM could be using the same vhost-user daemon and
> > avoid having to write yet another RNG driver.
> >
> > Signed-off-by: Mathieu Poirier <mathieu.poirier@linaro.org>
> > ---
> >  hw/virtio/Kconfig                  |   5 +
> >  hw/virtio/meson.build              |   1 +
> 
> FWIW there are simple merge failures for the meson and Kconfig parts due
> to I2C being merged.
> 

Right, merging I2C before this set will definitely break things.

> <snip>
> > +
> > +    rng->vhost_dev.nvqs = 1;
> > +    rng->vhost_dev.vqs = g_new0(struct vhost_virtqueue, 
> > rng->vhost_dev.nvqs);
> > +    if (!rng->vhost_dev.vqs) {
> > +        error_setg_errno(errp, -1, "memory allocation failed");
> > +        goto vhost_dev_init_failed;
> > +    }
> 
> g_new0 will abort on memory allocation failure (which is fine for
> userspace ;-) so you don't need the check and erro handling exit here.
> 

Ok, I'll fix this.

> > +
> > +    ret = vhost_dev_init(&rng->vhost_dev, &rng->vhost_user,
> > +                         VHOST_BACKEND_TYPE_USER, 0, errp);
> > +    if (ret < 0) {
> > +        error_setg_errno(errp, -ret, "vhost_dev_init() failed");
> > +        goto vhost_dev_init_failed;
> > +    }
> > +
> > +    qemu_chr_fe_set_handlers(&rng->chardev, NULL, NULL, vu_rng_event, NULL,
> > +                             dev, NULL, true);
> > +
> > +    return;
> > +
> > +vhost_dev_init_failed:
> > +    virtio_delete_queue(rng->req_vq);
> > +virtio_add_queue_failed:
> > +    virtio_cleanup(vdev);
> > +    vhost_user_cleanup(&rng->vhost_user);
> > +}
> > +
> > +static void vu_rng_device_unrealize(DeviceState *dev)
> > +{
> > +    VirtIODevice *vdev = VIRTIO_DEVICE(dev);
> > +    VHostUserRNG *rng = VHOST_USER_RNG(dev);
> > +
> > +    vu_rng_set_status(vdev, 0);
> > +
> > +    vhost_dev_cleanup(&rng->vhost_dev);
> > +    g_free(rng->vhost_dev.vqs);
> > +    rng->vhost_dev.vqs = NULL;
> > +    virtio_delete_queue(rng->req_vq);
> > +    virtio_cleanup(vdev);
> > +    vhost_user_cleanup(&rng->vhost_user);
> > +}
> > +
> > +static const VMStateDescription vu_rng_vmstate = {
> > +    .name = "vhost-user-rng",
> > +    .unmigratable = 1,
> > +};
> > +
> > +static Property vu_rng_properties[] = {
> > +    DEFINE_PROP_CHR("chardev", VHostUserRNG, chardev),
> > +    DEFINE_PROP_END_OF_LIST(),
> > +};
> > +
> > +static void vu_rng_class_init(ObjectClass *klass, void *data)
> > +{
> > +    DeviceClass *dc = DEVICE_CLASS(klass);
> > +    VirtioDeviceClass *vdc = VIRTIO_DEVICE_CLASS(klass);
> > +
> > +    device_class_set_props(dc, vu_rng_properties);
> > +    dc->vmsd = &vu_rng_vmstate;
> > +    set_bit(DEVICE_CATEGORY_INPUT, dc->categories);
> > +
> > +    vdc->realize = vu_rng_device_realize;
> > +    vdc->unrealize = vu_rng_device_unrealize;
> > +    vdc->get_features = vu_rng_get_features;
> > +    vdc->set_status = vu_rng_set_status;
> > +    vdc->guest_notifier_mask = vu_rng_guest_notifier_mask;
> > +    vdc->guest_notifier_pending = vu_rng_guest_notifier_pending;
> > +}
> > +
> > +static const TypeInfo vu_rng_info = {
> > +    .name = TYPE_VHOST_USER_RNG,
> > +    .parent = TYPE_VIRTIO_DEVICE,
> > +    .instance_size = sizeof(VHostUserRNG),
> > +    .class_init = vu_rng_class_init,
> > +};
> > +
> > +static void vu_rng_register_types(void)
> > +{
> > +    type_register_static(&vu_rng_info);
> > +}
> > +
> > +type_init(vu_rng_register_types)
> > diff --git a/include/hw/virtio/vhost-user-rng.h 
> > b/include/hw/virtio/vhost-user-rng.h
> > new file mode 100644
> > index 000000000000..071539996d1d
> > --- /dev/null
> > +++ b/include/hw/virtio/vhost-user-rng.h
> > @@ -0,0 +1,33 @@
> > +/*
> > + * Vhost-user RNG virtio device
> > + *
> > + * Copyright (c) 2021 Mathieu Poirier <mathieu.poirier@linaro.org>
> > + *
> > + * SPDX-License-Identifier: GPL-2.0-or-later
> > + */
> > +
> > +#ifndef _QEMU_VHOST_USER_RNG_H
> > +#define _QEMU_VHOST_USER_RNG_H
> > +
> > +#include "hw/virtio/virtio.h"
> > +#include "hw/virtio/vhost.h"
> > +#include "hw/virtio/vhost-user.h"
> > +#include "chardev/char-fe.h"
> > +
> > +#define TYPE_VHOST_USER_RNG "vhost-user-rng"
> > +OBJECT_DECLARE_SIMPLE_TYPE(VHostUserRNG, VHOST_USER_RNG)
> > +
> > +struct VHostUserRNG {
> > +    /*< private >*/
> > +    VirtIODevice parent;
> > +    CharBackend chardev;
> > +    struct vhost_virtqueue *vhost_vq;
> > +    struct vhost_dev vhost_dev;
> > +    VhostUserState vhost_user;
> > +    VirtQueue *req_vq;
> > +    bool connected;
> > +
> > +    /*< public >*/
> > +};
> > +
> > +#endif /* _QEMU_VHOST_USER_RNG_H */
> 
> Otherwise:
> 
> Reviewed-by: Alex Bennée <alex.bennee@linaro.org>

Thanks for taking the time to review this set.

> 
> -- 
> Alex Bennée



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