Re: [PATCH v3 1/2] vhost: Add rbtree vdpa_mem_tree to saved the counted mem

[Cindy Lu]

On Sun, Jun 26, 2022 at 6:01 PM Michael S. Tsirkin <mst@xxxxxxxxxx> wrote:
>
> On Sun, Jun 26, 2022 at 05:04:08PM +0800, Cindy Lu wrote:
> > We count pinned_vm as follow in vhost-vDPA
> >
> > lock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;
> > if (npages + atomic64_read(&dev->mm->pinned_vm) > lock_limit) {
> >          ret = -ENOMEM;
> >          goto unlock;
> > }
> > This means if we have two vDPA devices for the same VM the pages
> > would be counted twice. So we add a tree to save the page that
> > counted and we will not count it again.
> >
> > Add vdpa_mem_tree to saved the mem that already counted.
> > use a hlist to saved the root for vdpa_mem_tree.
> >
> > Signed-off-by: Cindy Lu <lulu@xxxxxxxxxx>
> > ---
> >  drivers/vhost/vhost.c | 63 +++++++++++++++++++++++++++++++++++++++++++
> >  drivers/vhost/vhost.h |  1 +
> >  2 files changed, 64 insertions(+)
> >
> > diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
> > index 40097826cff0..4ca8b1ed944b 100644
> > --- a/drivers/vhost/vhost.c
> > +++ b/drivers/vhost/vhost.c
> > @@ -32,6 +32,8 @@
> >  #include <linux/kcov.h>
> >
> >  #include "vhost.h"
> > +#include <linux/hashtable.h>
> > +#include <linux/jhash.h>
> >
> >  static ushort max_mem_regions = 64;
> >  module_param(max_mem_regions, ushort, 0444);
> > @@ -49,6 +51,14 @@ enum {
> >  #define vhost_used_event(vq) ((__virtio16 __user *)&vq->avail->ring[vq->num])
> >  #define vhost_avail_event(vq) ((__virtio16 __user *)&vq->used->ring[vq->num])
> >
> > +struct vhost_vdpa_rbtree_node {
> > +     struct hlist_node node;
> > +     struct rb_root_cached vdpa_mem_tree;
> > +     struct mm_struct *mm_using;
> > +};
> > +static DECLARE_HASHTABLE(vhost_vdpa_rbtree_hlist, 8);
> > +int vhost_vdpa_rbtree_hlist_status;
> > +
> >  #ifdef CONFIG_VHOST_CROSS_ENDIAN_LEGACY
> >  static void vhost_disable_cross_endian(struct vhost_virtqueue *vq)
> >  {
>
> Are you trying to save some per-mm information here?
> Can't we just add it to mm_struct?
>
yes, this is a per-mm information, but I have checked with jason before,
seems it maybe difficult to change the mm_struct in upstream
so I add an to add a hlist  instead
Thanks
Cindy

>
>
> > @@ -571,6 +581,51 @@ static void vhost_detach_mm(struct vhost_dev *dev)
> >       dev->mm = NULL;
> >  }
> >
> > +struct rb_root_cached *vhost_vdpa_get_mem_tree(struct mm_struct *mm)
> > +{
> > +     struct vhost_vdpa_rbtree_node *rbtree_root = NULL;
> > +     struct rb_root_cached *vdpa_tree;
> > +     u32 key;
> > +
> > +     /* No hased table, init one */
> > +     if (vhost_vdpa_rbtree_hlist_status == 0) {
> > +             hash_init(vhost_vdpa_rbtree_hlist);
> > +             vhost_vdpa_rbtree_hlist_status = 1;
> > +     }
> > +
> > +     key = jhash_1word((u64)mm, JHASH_INITVAL);
> > +     hash_for_each_possible(vhost_vdpa_rbtree_hlist, rbtree_root, node,
> > +                            key) {
> > +             if (rbtree_root->mm_using == mm)
> > +                     return &(rbtree_root->vdpa_mem_tree);
> > +     }
> > +     rbtree_root = kmalloc(sizeof(*rbtree_root), GFP_KERNEL);
> > +     if (!rbtree_root)
> > +             return NULL;
> > +     rbtree_root->mm_using = mm;
> > +     rbtree_root->vdpa_mem_tree = RB_ROOT_CACHED;
> > +     hash_add(vhost_vdpa_rbtree_hlist, &rbtree_root->node, key);
> > +     vdpa_tree = &(rbtree_root->vdpa_mem_tree);
> > +     return vdpa_tree;
> > +}
> > +
> > +void vhost_vdpa_relase_mem_tree(struct mm_struct *mm)
> > +{
> > +     struct vhost_vdpa_rbtree_node *rbtree_root = NULL;
> > +     u32 key;
> > +
> > +     key = jhash_1word((u64)mm, JHASH_INITVAL);
> > +
> > +     /* No hased table, init one */
> > +     hash_for_each_possible(vhost_vdpa_rbtree_hlist, rbtree_root, node,
> > +                            key) {
> > +             if (rbtree_root->mm_using == mm) {
> > +                     hash_del(&rbtree_root->node);
> > +                     kfree(rbtree_root);
> > +             }
> > +     }
> > +}
> > +
> >  /* Caller should have device mutex */
> >  long vhost_dev_set_owner(struct vhost_dev *dev)
> >  {
> > @@ -605,6 +660,11 @@ long vhost_dev_set_owner(struct vhost_dev *dev)
> >       err = vhost_dev_alloc_iovecs(dev);
> >       if (err)
> >               goto err_cgroup;
> > +     dev->vdpa_mem_tree = vhost_vdpa_get_mem_tree(dev->mm);
> > +     if (dev->vdpa_mem_tree == NULL) {
> > +             err = -ENOMEM;
> > +             goto err_cgroup;
> > +     }
> >
> >       return 0;
> >  err_cgroup:
> > @@ -613,6 +673,7 @@ long vhost_dev_set_owner(struct vhost_dev *dev)
> >               dev->worker = NULL;
> >       }
> >  err_worker:
> > +     vhost_vdpa_relase_mem_tree(dev->mm);
> >       vhost_detach_mm(dev);
> >       dev->kcov_handle = 0;
> >  err_mm:
> > @@ -710,6 +771,8 @@ void vhost_dev_cleanup(struct vhost_dev *dev)
> >               dev->worker = NULL;
> >               dev->kcov_handle = 0;
> >       }
> > +
> > +     vhost_vdpa_relase_mem_tree(dev->mm);
> >       vhost_detach_mm(dev);
> >  }
> >  EXPORT_SYMBOL_GPL(vhost_dev_cleanup);
> > diff --git a/drivers/vhost/vhost.h b/drivers/vhost/vhost.h
> > index d9109107af08..84de33de3abf 100644
> > --- a/drivers/vhost/vhost.h
> > +++ b/drivers/vhost/vhost.h
> > @@ -160,6 +160,7 @@ struct vhost_dev {
> >       int byte_weight;
> >       u64 kcov_handle;
> >       bool use_worker;
> > +     struct rb_root_cached *vdpa_mem_tree;
> >       int (*msg_handler)(struct vhost_dev *dev, u32 asid,
> >                          struct vhost_iotlb_msg *msg);
> >  };
> > --
> > 2.34.3
>