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Tsirkin" Cc: Jason Wang , Xuan Zhuo , Cindy Lu , Laurent Vivier , Stefano Garzarella , linux-kernel@vger.kernel.org, Maxime Coquelin , Yongji Xie , =?UTF-8?q?Eugenio=20P=C3=A9rez?= , virtualization@lists.linux.dev Subject: [PATCH 1/6] vduse: ensure vq->ready access is smp safe Date: Wed, 28 Jan 2026 13:45:19 +0100 Message-ID: <20260128124524.875271-2-eperezma@redhat.com> In-Reply-To: <20260128124524.875271-1-eperezma@redhat.com> References: <20260128124524.875271-1-eperezma@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 The vduse_vdpa_set_vq_ready can be called in the lifetime of the device well after initial setup, and the device can read it afterwards. Ensure that reads and writes to vq->ready are SMP safe so that the caller can trust that virtqueue kicks and calls behave as expected immediately after the operation returns. Signed-off-by: Eugenio P=C3=A9rez --- drivers/vdpa/vdpa_user/vduse_dev.c | 34 +++++++++++++++++++++++------- 1 file changed, 26 insertions(+), 8 deletions(-) diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c b/drivers/vdpa/vdpa_user/vd= use_dev.c index 73d1d517dc6c..a4963aaf9332 100644 --- a/drivers/vdpa/vdpa_user/vduse_dev.c +++ b/drivers/vdpa/vdpa_user/vduse_dev.c @@ -460,6 +460,24 @@ static __poll_t vduse_dev_poll(struct file *file, poll= _table *wait) return mask; } =20 +static bool vduse_vq_get_ready(const struct vduse_virtqueue *vq) +{ + /* + * Paired with vduse_vq_set_ready smp_store, as the driver may modify + * it while the VDUSE instance is reading it. + */ + return smp_load_acquire(&vq->ready); +} + +static void vduse_vq_set_ready(struct vduse_virtqueue *vq, bool ready) +{ + /* + * Paired with vduse_vq_get_ready smp_load, as the driver may modify + * it while the VDUSE instance is reading it. + */ + smp_store_release(&vq->ready, ready); +} + static void vduse_dev_reset(struct vduse_dev *dev) { int i; @@ -486,7 +504,7 @@ static void vduse_dev_reset(struct vduse_dev *dev) for (i =3D 0; i < dev->vq_num; i++) { struct vduse_virtqueue *vq =3D dev->vqs[i]; =20 - vq->ready =3D false; + vduse_vq_set_ready(vq, false); vq->desc_addr =3D 0; vq->driver_addr =3D 0; vq->device_addr =3D 0; @@ -529,7 +547,7 @@ static int vduse_vdpa_set_vq_address(struct vdpa_device= *vdpa, u16 idx, static void vduse_vq_kick(struct vduse_virtqueue *vq) { spin_lock(&vq->kick_lock); - if (!vq->ready) + if (!vduse_vq_get_ready(vq)) goto unlock; =20 if (vq->kickfd) @@ -598,7 +616,7 @@ static void vduse_vdpa_set_vq_ready(struct vdpa_device = *vdpa, struct vduse_dev *dev =3D vdpa_to_vduse(vdpa); struct vduse_virtqueue *vq =3D dev->vqs[idx]; =20 - vq->ready =3D ready; + vduse_vq_set_ready(vq, ready); } =20 static bool vduse_vdpa_get_vq_ready(struct vdpa_device *vdpa, u16 idx) @@ -606,7 +624,7 @@ static bool vduse_vdpa_get_vq_ready(struct vdpa_device = *vdpa, u16 idx) struct vduse_dev *dev =3D vdpa_to_vduse(vdpa); struct vduse_virtqueue *vq =3D dev->vqs[idx]; =20 - return vq->ready; + return vduse_vq_get_ready(vq); } =20 static int vduse_vdpa_set_vq_state(struct vdpa_device *vdpa, u16 idx, @@ -1097,7 +1115,7 @@ static int vduse_kickfd_setup(struct vduse_dev *dev, if (vq->kickfd) eventfd_ctx_put(vq->kickfd); vq->kickfd =3D ctx; - if (vq->ready && vq->kicked && vq->kickfd) { + if (vduse_vq_get_ready(vq) && vq->kicked && vq->kickfd) { eventfd_signal(vq->kickfd); vq->kicked =3D false; } @@ -1133,7 +1151,7 @@ static void vduse_vq_irq_inject(struct work_struct *w= ork) struct vduse_virtqueue, inject); =20 spin_lock_bh(&vq->irq_lock); - if (vq->ready && vq->cb.callback) + if (vduse_vq_get_ready(vq) && vq->cb.callback) vq->cb.callback(vq->cb.private); spin_unlock_bh(&vq->irq_lock); } @@ -1146,7 +1164,7 @@ static bool vduse_vq_signal_irqfd(struct vduse_virtqu= eue *vq) return false; =20 spin_lock_irq(&vq->irq_lock); - if (vq->ready && vq->cb.trigger) { + if (vduse_vq_get_ready(vq) && vq->cb.trigger) { eventfd_signal(vq->cb.trigger); signal =3D true; } @@ -1500,7 +1518,7 @@ static long vduse_dev_ioctl(struct file *file, unsign= ed int cmd, vq_info.split.avail_index =3D vq->state.split.avail_index; =20 - vq_info.ready =3D vq->ready; + vq_info.ready =3D vduse_vq_get_ready(vq); =20 ret =3D -EFAULT; if (copy_to_user(argp, &vq_info, sizeof(vq_info))) --=20 2.52.0