RE: [RFC PATCH v2 09/19] vhost: support ASID in IOTLB API

From: Gautam Dawar
Date: Fri Mar 04 2022 - 12:52:30 EST

-----Original Message-----
From: Eugenio Perez Martin <eperezma@xxxxxxxxxx>
Sent: Friday, March 4, 2022 3:55 PM
To: Gautam Dawar <gdawar@xxxxxxxxxx>
Cc: Gautam Dawar <gdawar@xxxxxxxxxx>; Martin Petrus Hubertus Habets <martinh@xxxxxxxxxx>; Harpreet Singh Anand <hanand@xxxxxxxxxx>; Tanuj Murlidhar Kamde <tanujk@xxxxxxxxxx>; Jason Wang <jasowang@xxxxxxxxxx>; Michael S. Tsirkin <mst@xxxxxxxxxx>; Zhu Lingshan <lingshan.zhu@xxxxxxxxx>; Stefano Garzarella <sgarzare@xxxxxxxxxx>; Xie Yongji <xieyongji@xxxxxxxxxxxxx>; Eli Cohen <elic@xxxxxxxxxx>; Si-Wei Liu <si-wei.liu@xxxxxxxxxx>; Parav Pandit <parav@xxxxxxxxxx>; Longpeng <longpeng2@xxxxxxxxxx>; virtualization <virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx>; linux-kernel@xxxxxxxxxxxxxxx; kvm list <kvm@xxxxxxxxxxxxxxx>; netdev@xxxxxxxxxxxxxxx
Subject: Re: [RFC PATCH v2 09/19] vhost: support ASID in IOTLB API

On Thu, Feb 24, 2022 at 10:26 PM Gautam Dawar <gautam.dawar@xxxxxxxxxx> wrote:
>
> This patches allows userspace to send ASID based IOTLB message to
> vhost. This idea is to use the reserved u32 field in the existing V2
> IOTLB message. Vhost device should advertise this capability via
> VHOST_BACKEND_F_IOTLB_ASID backend feature.
>
> Signed-off-by: Jason Wang <jasowang@xxxxxxxxxx>
> Signed-off-by: Gautam Dawar <gdawar@xxxxxxxxxx>
> ---
> drivers/vhost/vdpa.c | 5 ++++-
> drivers/vhost/vhost.c | 23 ++++++++++++++++++-----
> drivers/vhost/vhost.h | 4 ++--
> include/uapi/linux/vhost_types.h | 6 +++++-
> 4 files changed, 29 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c index
> 6bf755f84d26..d0aacc0cc79a 100644
> --- a/drivers/vhost/vdpa.c
> +++ b/drivers/vhost/vdpa.c
> @@ -836,7 +836,7 @@ static int vhost_vdpa_process_iotlb_update(struct vhost_vdpa *v,
> msg->perm); }
>
> -static int vhost_vdpa_process_iotlb_msg(struct vhost_dev *dev,
> +static int vhost_vdpa_process_iotlb_msg(struct vhost_dev *dev, u32
> +asid,
> struct vhost_iotlb_msg *msg)
> {
> struct vhost_vdpa *v = container_of(dev, struct vhost_vdpa,
> vdev); @@ -847,6 +847,9 @@ static int
> vhost_vdpa_process_iotlb_msg(struct vhost_dev *dev,
>
> mutex_lock(&dev->mutex);
>
> + if (asid != 0)
> + return -EINVAL;
> +

Should we check for asid != 0 before acquiring the mutex? Otherwise the code never releases it.
[GD>>] Yes, you are right. Will fix this in next revision.

> r = vhost_dev_check_owner(dev);
> if (r)
> goto unlock;
> diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c index
> 59edb5a1ffe2..1f514d98f0de 100644
> --- a/drivers/vhost/vhost.c
> +++ b/drivers/vhost/vhost.c
> @@ -468,7 +468,7 @@ void vhost_dev_init(struct vhost_dev *dev,
> struct vhost_virtqueue **vqs, int nvqs,
> int iov_limit, int weight, int byte_weight,
> bool use_worker,
> - int (*msg_handler)(struct vhost_dev *dev,
> + int (*msg_handler)(struct vhost_dev *dev, u32
> + asid,
> struct vhost_iotlb_msg *msg))
> {
> struct vhost_virtqueue *vq;
> @@ -1090,11 +1090,14 @@ static bool umem_access_ok(u64 uaddr, u64 size, int access)
> return true;
> }
>
> -static int vhost_process_iotlb_msg(struct vhost_dev *dev,
> +static int vhost_process_iotlb_msg(struct vhost_dev *dev, u32 asid,
> struct vhost_iotlb_msg *msg) {
> int ret = 0;
>
> + if (asid != 0)
> + return -EINVAL;
> +
> mutex_lock(&dev->mutex);
> vhost_dev_lock_vqs(dev);
> switch (msg->type) {
> @@ -1141,6 +1144,7 @@ ssize_t vhost_chr_write_iter(struct vhost_dev *dev,
> struct vhost_iotlb_msg msg;
> size_t offset;
> int type, ret;
> + u32 asid = 0;
>
> ret = copy_from_iter(&type, sizeof(type), from);
> if (ret != sizeof(type)) {
> @@ -1156,7 +1160,16 @@ ssize_t vhost_chr_write_iter(struct vhost_dev *dev,
> offset = offsetof(struct vhost_msg, iotlb) - sizeof(int);
> break;
> case VHOST_IOTLB_MSG_V2:
> - offset = sizeof(__u32);
> + if (vhost_backend_has_feature(dev->vqs[0],
> + VHOST_BACKEND_F_IOTLB_ASID)) {
> + ret = copy_from_iter(&asid, sizeof(asid), from);
> + if (ret != sizeof(asid)) {
> + ret = -EINVAL;
> + goto done;
> + }
> + offset = sizeof(__u16);
> + } else
> + offset = sizeof(__u32);
> break;
> default:
> ret = -EINVAL;
> @@ -1171,9 +1184,9 @@ ssize_t vhost_chr_write_iter(struct vhost_dev *dev,
> }
>
> if (dev->msg_handler)
> - ret = dev->msg_handler(dev, &msg);
> + ret = dev->msg_handler(dev, asid, &msg);
> else
> - ret = vhost_process_iotlb_msg(dev, &msg);
> + ret = vhost_process_iotlb_msg(dev, asid, &msg);
> if (ret) {
> ret = -EFAULT;
> goto done;
> diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h index
> 638bb640d6b4..9f238d6c7b58 100644
> --- a/drivers/vhost/vhost.h
> +++ b/drivers/vhost/vhost.h
> @@ -161,7 +161,7 @@ struct vhost_dev {
> int byte_weight;
> u64 kcov_handle;
> bool use_worker;
> - int (*msg_handler)(struct vhost_dev *dev,
> + int (*msg_handler)(struct vhost_dev *dev, u32 asid,
> struct vhost_iotlb_msg *msg); };
>
> @@ -169,7 +169,7 @@ bool vhost_exceeds_weight(struct vhost_virtqueue
> *vq, int pkts, int total_len); void vhost_dev_init(struct vhost_dev *, struct vhost_virtqueue **vqs,
> int nvqs, int iov_limit, int weight, int byte_weight,
> bool use_worker,
> - int (*msg_handler)(struct vhost_dev *dev,
> + int (*msg_handler)(struct vhost_dev *dev, u32
> + asid,
> struct vhost_iotlb_msg *msg));
> long vhost_dev_set_owner(struct vhost_dev *dev); bool
> vhost_dev_has_owner(struct vhost_dev *dev); diff --git
> a/include/uapi/linux/vhost_types.h b/include/uapi/linux/vhost_types.h
> index 76ee7016c501..634cee485abb 100644
> --- a/include/uapi/linux/vhost_types.h
> +++ b/include/uapi/linux/vhost_types.h
> @@ -87,7 +87,7 @@ struct vhost_msg {
>
> struct vhost_msg_v2 {
> __u32 type;
> - __u32 reserved;
> + __u32 asid;
> union {
> struct vhost_iotlb_msg iotlb;
> __u8 padding[64];
> @@ -157,5 +157,9 @@ struct vhost_vdpa_iova_range { #define
> VHOST_BACKEND_F_IOTLB_MSG_V2 0x1
> /* IOTLB can accept batching hints */ #define
> VHOST_BACKEND_F_IOTLB_BATCH 0x2
> +/* IOTLB can accept address space identifier through V2 type of IOTLB
> + * message
> + */
> +#define VHOST_BACKEND_F_IOTLB_ASID 0x3
>
> #endif
> --
> 2.25.0
>