Re: [PATCH net-next V4 5/5] vhost: access vq metadata through kernel virtual address

Michael S. Tsirkin
2019-01-25T03:00:27Z

On Thu, Jan 24, 2019 at 12:07:54PM +0800, Jason Wang wrote:
> > Meanwhile, could you pls post data comparing this last patch with the
> > below? This removes the speculation barrier replacing it with a
> > (useless but at least more lightweight) data dependency.
>
>
> SMAP off
>
> Your patch: 7.2MPPs
>
> vmap: 7.4Mpps

OK so while we keep looking into vmap, why don't we merge something like
the below? Seems quite straight forward ...

> I don't test SMAP on, since it will be much slow for sure.
>
> Thanks
>
>
> >
> > Thanks!
> >
> >
> > diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
> > index bac939af8dbb..352ee7e14476 100644
> > --- a/drivers/vhost/vhost.c
> > +++ b/drivers/vhost/vhost.c
> > @@ -739,7 +739,7 @@ static int vhost_copy_to_user(struct vhost_virtqueue *vq, void __user *to,
> > int ret;
> > if (!vq->iotlb)
> > - return __copy_to_user(to, from, size);
> > + return copy_to_user(to, from, size);
> > else {
> > /* This function should be called after iotlb
> > * prefetch, which means we're sure that all vq
> > @@ -752,7 +752,7 @@ static int vhost_copy_to_user(struct vhost_virtqueue *vq, void __user *to,
> > VHOST_ADDR_USED);
> > if (uaddr)
> > - return __copy_to_user(uaddr, from, size);
> > + return copy_to_user(uaddr, from, size);
> > ret = translate_desc(vq, (u64)(uintptr_t)to, size, vq->iotlb_iov,
> > ARRAY_SIZE(vq->iotlb_iov),
> > @@ -774,7 +774,7 @@ static int vhost_copy_from_user(struct vhost_virtqueue *vq, void *to,
> > int ret;
> > if (!vq->iotlb)
> > - return __copy_from_user(to, from, size);
> > + return copy_from_user(to, from, size);
> > else {
> > /* This function should be called after iotlb
> > * prefetch, which means we're sure that vq
> > @@ -787,7 +787,7 @@ static int vhost_copy_from_user(struct vhost_virtqueue *vq, void *to,
> > struct iov_iter f;
> > if (uaddr)
> > - return __copy_from_user(to, uaddr, size);
> > + return copy_from_user(to, uaddr, size);
> > ret = translate_desc(vq, (u64)(uintptr_t)from, size, vq->iotlb_iov,
> > ARRAY_SIZE(vq->iotlb_iov),
> > @@ -855,13 +855,13 @@ static inline void __user *__vhost_get_user(struct vhost_virtqueue *vq,
> > ({ \
> > int ret = -EFAULT; \
> > if (!vq->iotlb) { \
> > - ret = __put_user(x, ptr); \
> > + ret = put_user(x, ptr); \
> > } else { \
> > __typeof__(ptr) to = \
> > (__typeof__(ptr)) __vhost_get_user(vq, ptr, \
> > sizeof(*ptr), VHOST_ADDR_USED); \
> > if (to != NULL) \
> > - ret = __put_user(x, to); \
> > + ret = put_user(x, to); \
> > else \
> > ret = -EFAULT; \
> > } \
> > @@ -872,14 +872,14 @@ static inline void __user *__vhost_get_user(struct vhost_virtqueue *vq,
> > ({ \
> > int ret; \
> > if (!vq->iotlb) { \
> > - ret = __get_user(x, ptr); \
> > + ret = get_user(x, ptr); \
> > } else { \
> > __typeof__(ptr) from = \
> > (__typeof__(ptr)) __vhost_get_user(vq, ptr, \
> > sizeof(*ptr), \
> > type); \
> > if (from != NULL) \
> > - ret = __get_user(x, from); \
> > + ret = get_user(x, from); \
> > else \
> > ret = -EFAULT; \
> > } \