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

["Michael S. Tsirkin" <mst@redhat.com>]

On Mon, Jun 27, 2022 at 04:12:57PM +0800, Cindy Lu wrote:
> On Sun, Jun 26, 2022 at 6:01 PM Michael S. Tsirkin <mst@redhat.com> 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@redhat.com>
> > > ---
> > >  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

Difficult how? You get more scrutiny if you try, for sure,
and you need to need to generalize it enough that it looks
useful outside the driver. But I guess that's good?

> >
> >
> > > @@ -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
> >

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