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Date: Tue, 4 Aug 2020 16:53:39 +0800
From: Jason Wang <jasowang@...hat.com>
To: "Zhu, Lingshan" <lingshan.zhu@...el.com>,
alex.williamson@...hat.com, mst@...hat.com, pbonzini@...hat.com,
sean.j.christopherson@...el.com, wanpengli@...cent.com
Cc: virtualization@...ts.linux-foundation.org, netdev@...r.kernel.org,
kvm@...r.kernel.org, eli@...lanox.com, shahafs@...lanox.com,
parav@...lanox.com
Subject: Re: [PATCH V5 1/6] vhost: introduce vhost_vring_call
On 2020/8/4 下午4:42, Zhu, Lingshan wrote:
>
>
> On 8/4/2020 4:38 PM, Jason Wang wrote:
>>
>> On 2020/7/31 下午2:55, Zhu Lingshan wrote:
>>> This commit introduces struct vhost_vring_call which replaced
>>> raw struct eventfd_ctx *call_ctx in struct vhost_virtqueue.
>>> Besides eventfd_ctx, it contains a spin lock and an
>>> irq_bypass_producer in its structure.
>>>
>>> Signed-off-by: Zhu Lingshan <lingshan.zhu@...el.com>
>>> Suggested-by: Jason Wang <jasowang@...hat.com>
>>> ---
>>> drivers/vhost/vdpa.c | 4 ++--
>>> drivers/vhost/vhost.c | 22 ++++++++++++++++------
>>> drivers/vhost/vhost.h | 9 ++++++++-
>>> 3 files changed, 26 insertions(+), 9 deletions(-)
>>>
>>> diff --git a/drivers/vhost/vdpa.c b/drivers/vhost/vdpa.c
>>> index a54b60d6623f..df3cf386b0cd 100644
>>> --- a/drivers/vhost/vdpa.c
>>> +++ b/drivers/vhost/vdpa.c
>>> @@ -96,7 +96,7 @@ static void handle_vq_kick(struct vhost_work *work)
>>> static irqreturn_t vhost_vdpa_virtqueue_cb(void *private)
>>> {
>>> struct vhost_virtqueue *vq = private;
>>> - struct eventfd_ctx *call_ctx = vq->call_ctx;
>>> + struct eventfd_ctx *call_ctx = vq->call_ctx.ctx;
>>> if (call_ctx)
>>> eventfd_signal(call_ctx, 1);
>>> @@ -382,7 +382,7 @@ static long vhost_vdpa_vring_ioctl(struct
>>> vhost_vdpa *v, unsigned int cmd,
>>> break;
>>> case VHOST_SET_VRING_CALL:
>>> - if (vq->call_ctx) {
>>> + if (vq->call_ctx.ctx) {
>>> cb.callback = vhost_vdpa_virtqueue_cb;
>>> cb.private = vq;
>>> } else {
>>> diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
>>> index d7b8df3edffc..9f1a845a9302 100644
>>> --- a/drivers/vhost/vhost.c
>>> +++ b/drivers/vhost/vhost.c
>>> @@ -298,6 +298,13 @@ static void vhost_vq_meta_reset(struct
>>> vhost_dev *d)
>>> __vhost_vq_meta_reset(d->vqs[i]);
>>> }
>>> +static void vhost_vring_call_reset(struct vhost_vring_call
>>> *call_ctx)
>>> +{
>>> + call_ctx->ctx = NULL;
>>> + memset(&call_ctx->producer, 0x0, sizeof(struct
>>> irq_bypass_producer));
>>> + spin_lock_init(&call_ctx->ctx_lock);
>>> +}
>>> +
>>> static void vhost_vq_reset(struct vhost_dev *dev,
>>> struct vhost_virtqueue *vq)
>>> {
>>> @@ -319,13 +326,13 @@ static void vhost_vq_reset(struct vhost_dev *dev,
>>> vq->log_base = NULL;
>>> vq->error_ctx = NULL;
>>> vq->kick = NULL;
>>> - vq->call_ctx = NULL;
>>> vq->log_ctx = NULL;
>>> vhost_reset_is_le(vq);
>>> vhost_disable_cross_endian(vq);
>>> vq->busyloop_timeout = 0;
>>> vq->umem = NULL;
>>> vq->iotlb = NULL;
>>> + vhost_vring_call_reset(&vq->call_ctx);
>>> __vhost_vq_meta_reset(vq);
>>> }
>>> @@ -685,8 +692,8 @@ void vhost_dev_cleanup(struct vhost_dev *dev)
>>> eventfd_ctx_put(dev->vqs[i]->error_ctx);
>>> if (dev->vqs[i]->kick)
>>> fput(dev->vqs[i]->kick);
>>> - if (dev->vqs[i]->call_ctx)
>>> - eventfd_ctx_put(dev->vqs[i]->call_ctx);
>>> + if (dev->vqs[i]->call_ctx.ctx)
>>> + eventfd_ctx_put(dev->vqs[i]->call_ctx.ctx);
>>> vhost_vq_reset(dev, dev->vqs[i]);
>>> }
>>> vhost_dev_free_iovecs(dev);
>>> @@ -1629,7 +1636,10 @@ long vhost_vring_ioctl(struct vhost_dev *d,
>>> unsigned int ioctl, void __user *arg
>>> r = PTR_ERR(ctx);
>>> break;
>>> }
>>> - swap(ctx, vq->call_ctx);
>>> +
>>> + spin_lock(&vq->call_ctx.ctx_lock);
>>> + swap(ctx, vq->call_ctx.ctx);
>>> + spin_unlock(&vq->call_ctx.ctx_lock);
>>> break;
>>> case VHOST_SET_VRING_ERR:
>>> if (copy_from_user(&f, argp, sizeof f)) {
>>> @@ -2440,8 +2450,8 @@ static bool vhost_notify(struct vhost_dev
>>> *dev, struct vhost_virtqueue *vq)
>>> void vhost_signal(struct vhost_dev *dev, struct vhost_virtqueue *vq)
>>> {
>>> /* Signal the Guest tell them we used something up. */
>>> - if (vq->call_ctx && vhost_notify(dev, vq))
>>> - eventfd_signal(vq->call_ctx, 1);
>>> + if (vq->call_ctx.ctx && vhost_notify(dev, vq))
>>> + eventfd_signal(vq->call_ctx.ctx, 1);
>>> }
>>> EXPORT_SYMBOL_GPL(vhost_signal);
>>> diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
>>> index c8e96a095d3b..38eb1aa3b68d 100644
>>> --- a/drivers/vhost/vhost.h
>>> +++ b/drivers/vhost/vhost.h
>>> @@ -13,6 +13,7 @@
>>> #include <linux/virtio_ring.h>
>>> #include <linux/atomic.h>
>>> #include <linux/vhost_iotlb.h>
>>> +#include <linux/irqbypass.h>
>>> struct vhost_work;
>>> typedef void (*vhost_work_fn_t)(struct vhost_work *work);
>>> @@ -60,6 +61,12 @@ enum vhost_uaddr_type {
>>> VHOST_NUM_ADDRS = 3,
>>> };
>>> +struct vhost_vring_call {
>>> + struct eventfd_ctx *ctx;
>>> + struct irq_bypass_producer producer;
>>> + spinlock_t ctx_lock;
>>
>>
>> It's not clear to me why we need ctx_lock here.
>>
>> Thanks
> Hi Jason,
>
> we use this lock to protect the eventfd_ctx and irq from race conditions,
We don't support irq notification from vDPA device driver in this
version, do we still have race condition?
Thanks
> are you suggesting a better name?
>
> Thanks
>>
>>
>>> +};
>>> +
>>> /* The virtqueue structure describes a queue attached to a device. */
>>> struct vhost_virtqueue {
>>> struct vhost_dev *dev;
>>> @@ -72,7 +79,7 @@ struct vhost_virtqueue {
>>> vring_used_t __user *used;
>>> const struct vhost_iotlb_map *meta_iotlb[VHOST_NUM_ADDRS];
>>> struct file *kick;
>>> - struct eventfd_ctx *call_ctx;
>>> + struct vhost_vring_call call_ctx;
>>> struct eventfd_ctx *error_ctx;
>>> struct eventfd_ctx *log_ctx;
>>
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