[net-next,v22,04/13] netdev: netdevice devmem allocator
Commit Message
Implement netdev devmem allocator. The allocator takes a given struct
netdev_dmabuf_binding as input and allocates net_iov from that
binding.
The allocation simply delegates to the binding's genpool for the
allocation logic and wraps the returned memory region in a net_iov
struct.
Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: Kaiyuan Zhang <kaiyuanz@google.com>
Signed-off-by: Mina Almasry <almasrymina@google.com>
Reviewed-by: Pavel Begunkov <asml.silence@gmail.com>
---
v20:
- Removed dma_addr field in dmabuf_genpool_chunk_owner not used in this
patch (moved to later patch where it's used).
v19:
- Don't reset dma_addr on allocation/free (Jakub)
v17:
- Don't acquire a binding ref for every allocation (Jakub).
v11:
- Fix extraneous inline directive (Paolo)
v8:
- Rename netdev_dmabuf_binding -> net_devmem_dmabuf_binding to avoid
patch-by-patch build error.
- Move niov->pp_magic/pp/pp_ref_counter usage to later patch to avoid
patch-by-patch build error.
v7:
- netdev_ -> net_devmem_* naming (Yunsheng).
v6:
- Add comment on net_iov_dma_addr to explain why we don't use
niov->dma_addr (Pavel)
- Refactor new functions into net/core/devmem.c (Pavel)
v1:
- Rename devmem -> dmabuf (David).
---
include/net/devmem.h | 13 +++++++++++++
include/net/netmem.h | 17 +++++++++++++++++
net/core/devmem.c | 38 ++++++++++++++++++++++++++++++++++++++
3 files changed, 68 insertions(+)
Comments
On Sun, 25 Aug 2024 04:15:02 +0000 Mina Almasry wrote:
> +void net_devmem_free_dmabuf(struct net_iov *niov)
> +{
> + struct net_devmem_dmabuf_binding *binding = net_iov_binding(niov);
> + unsigned long dma_addr = net_devmem_get_dma_addr(niov);
> +
> + if (gen_pool_has_addr(binding->chunk_pool, dma_addr, PAGE_SIZE))
> + gen_pool_free(binding->chunk_pool, dma_addr, PAGE_SIZE);
Is the check necessary for correctness? Should it perhaps be a WARN
under DEBUG_NET instead? The rest LGTM:
Reviewed-by: Jakub Kicinski <kuba@kernel.org>
On Tue, Aug 27, 2024 at 7:15 PM Jakub Kicinski <kuba@kernel.org> wrote:
>
> On Sun, 25 Aug 2024 04:15:02 +0000 Mina Almasry wrote:
> > +void net_devmem_free_dmabuf(struct net_iov *niov)
> > +{
> > + struct net_devmem_dmabuf_binding *binding = net_iov_binding(niov);
> > + unsigned long dma_addr = net_devmem_get_dma_addr(niov);
> > +
> > + if (gen_pool_has_addr(binding->chunk_pool, dma_addr, PAGE_SIZE))
> > + gen_pool_free(binding->chunk_pool, dma_addr, PAGE_SIZE);
>
> Is the check necessary for correctness? Should it perhaps be a WARN
> under DEBUG_NET instead? The rest LGTM:
>
Not really necessary for correctness per se, but if we try to free a
dma_addr that is not in a gen_pool (due to some other bug in the
code), then gen_pool_free ends up BUG_ON, crashing the kernel.
Arguably gen_pool_free should not BUG_ON, but I think that's an old
API, and existing call sites have worked around the BUG_ON by doing a
gen_pool_has_addr check like I do here, for example kernel/dma/pool.c.
So I did not seek to change this established behavior.
I think WARN seems fine to me, but maybe not under DEBUG_NET. I don't
want production code crashing due to this error, if it's OK with you.
Unless I hear otherwise I'll add a WARN without debug here.
> Reviewed-by: Jakub Kicinski <kuba@kernel.org>
>
Thanks!
On Wed, 28 Aug 2024 00:20:23 -0700 Mina Almasry wrote:
> > On Sun, 25 Aug 2024 04:15:02 +0000 Mina Almasry wrote:
> > > +void net_devmem_free_dmabuf(struct net_iov *niov)
> > > +{
> > > + struct net_devmem_dmabuf_binding *binding = net_iov_binding(niov);
> > > + unsigned long dma_addr = net_devmem_get_dma_addr(niov);
> > > +
> > > + if (gen_pool_has_addr(binding->chunk_pool, dma_addr, PAGE_SIZE))
> > > + gen_pool_free(binding->chunk_pool, dma_addr, PAGE_SIZE);
> >
> > Is the check necessary for correctness? Should it perhaps be a WARN
> > under DEBUG_NET instead? The rest LGTM:
> >
>
> Not really necessary for correctness per se, but if we try to free a
> dma_addr that is not in a gen_pool (due to some other bug in the
> code), then gen_pool_free ends up BUG_ON, crashing the kernel.
>
> Arguably gen_pool_free should not BUG_ON, but I think that's an old
> API, and existing call sites have worked around the BUG_ON by doing a
> gen_pool_has_addr check like I do here, for example kernel/dma/pool.c.
> So I did not seek to change this established behavior.
>
> I think WARN seems fine to me, but maybe not under DEBUG_NET. I don't
> want production code crashing due to this error, if it's OK with you.
>
> Unless I hear otherwise I'll add a WARN without debug here.
WARN makes sense, I didn't know about the BUG_ON() hiding inside
gen_pool :(
@@ -72,7 +72,20 @@ void net_devmem_unbind_dmabuf(struct net_devmem_dmabuf_binding *binding);
int net_devmem_bind_dmabuf_to_queue(struct net_device *dev, u32 rxq_idx,
struct net_devmem_dmabuf_binding *binding);
void dev_dmabuf_uninstall(struct net_device *dev);
+struct net_iov *
+net_devmem_alloc_dmabuf(struct net_devmem_dmabuf_binding *binding);
+void net_devmem_free_dmabuf(struct net_iov *ppiov);
#else
+static inline struct net_iov *
+net_devmem_alloc_dmabuf(struct net_devmem_dmabuf_binding *binding)
+{
+ return NULL;
+}
+
+static inline void net_devmem_free_dmabuf(struct net_iov *ppiov)
+{
+}
+
static inline void
__net_devmem_dmabuf_binding_free(struct net_devmem_dmabuf_binding *binding)
{
@@ -16,6 +16,23 @@ struct net_iov {
struct dmabuf_genpool_chunk_owner *owner;
};
+static inline struct dmabuf_genpool_chunk_owner *
+net_iov_owner(const struct net_iov *niov)
+{
+ return niov->owner;
+}
+
+static inline unsigned int net_iov_idx(const struct net_iov *niov)
+{
+ return niov - net_iov_owner(niov)->niovs;
+}
+
+static inline struct net_devmem_dmabuf_binding *
+net_iov_binding(const struct net_iov *niov)
+{
+ return net_iov_owner(niov)->binding;
+}
+
/* netmem */
/**
@@ -35,6 +35,14 @@ static void net_devmem_dmabuf_free_chunk_owner(struct gen_pool *genpool,
kfree(owner);
}
+static dma_addr_t net_devmem_get_dma_addr(const struct net_iov *niov)
+{
+ struct dmabuf_genpool_chunk_owner *owner = net_iov_owner(niov);
+
+ return owner->base_dma_addr +
+ ((dma_addr_t)net_iov_idx(niov) << PAGE_SHIFT);
+}
+
void __net_devmem_dmabuf_binding_free(struct net_devmem_dmabuf_binding *binding)
{
size_t size, avail;
@@ -57,6 +65,36 @@ void __net_devmem_dmabuf_binding_free(struct net_devmem_dmabuf_binding *binding)
kfree(binding);
}
+struct net_iov *
+net_devmem_alloc_dmabuf(struct net_devmem_dmabuf_binding *binding)
+{
+ struct dmabuf_genpool_chunk_owner *owner;
+ unsigned long dma_addr;
+ struct net_iov *niov;
+ ssize_t offset;
+ ssize_t index;
+
+ dma_addr = gen_pool_alloc_owner(binding->chunk_pool, PAGE_SIZE,
+ (void **)&owner);
+ if (!dma_addr)
+ return NULL;
+
+ offset = dma_addr - owner->base_dma_addr;
+ index = offset / PAGE_SIZE;
+ niov = &owner->niovs[index];
+
+ return niov;
+}
+
+void net_devmem_free_dmabuf(struct net_iov *niov)
+{
+ struct net_devmem_dmabuf_binding *binding = net_iov_binding(niov);
+ unsigned long dma_addr = net_devmem_get_dma_addr(niov);
+
+ if (gen_pool_has_addr(binding->chunk_pool, dma_addr, PAGE_SIZE))
+ gen_pool_free(binding->chunk_pool, dma_addr, PAGE_SIZE);
+}
+
void net_devmem_unbind_dmabuf(struct net_devmem_dmabuf_binding *binding)
{
struct netdev_rx_queue *rxq;