On Thu, 2014-03-06 at 21:48 +0000, Zoltan Kiss wrote:tx_copy_ops will be removed in the next patch. Yes, for grant_copy_op we allocate it separately, because it has MAX_SKB_FRAGS * XEN_NETIF_RX_RING_SIZE elements, but that's for the RX thread
@@ -135,13 +146,31 @@ struct xenvif {
pending_ring_idx_t pending_cons;
u16 pending_ring[MAX_PENDING_REQS];
struct pending_tx_info pending_tx_info[MAX_PENDING_REQS];
+ grant_handle_t grant_tx_handle[MAX_PENDING_REQS];
/* Coalescing tx requests before copying makes number of grant
* copy ops greater or equal to number of slots required. In
* worst case a tx request consumes 2 gnttab_copy.
*/
struct gnttab_copy tx_copy_ops[2*MAX_PENDING_REQS];
-
+ struct gnttab_map_grant_ref tx_map_ops[MAX_PENDING_REQS];
+ struct gnttab_unmap_grant_ref tx_unmap_ops[MAX_PENDING_REQS];
I wonder if we should break some of these arrays into separate
allocations? Wasn't there a problem with sizeof(struct xenvif) at one
point?
Not here, but in a later patch 9 will be replaced with worst_case_skb_lifetime.
diff --git a/drivers/net/xen-netback/interface.c b/drivers/net/xen-netback/interface.c
index bc32627..1fe9fe5 100644
--- a/drivers/net/xen-netback/interface.c
+++ b/drivers/net/xen-netback/interface.c
@@ -493,6 +533,23 @@ void xenvif_disconnect(struct xenvif *vif)
void xenvif_free(struct xenvif *vif)
{
+ int i, unmap_timeout = 0;
+
+ for (i = 0; i < MAX_PENDING_REQS; ++i) {
+ if (vif->grant_tx_handle[i] != NETBACK_INVALID_HANDLE) {
+ unmap_timeout++;
+ schedule_timeout(msecs_to_jiffies(1000));
+ if (unmap_timeout > 9 &&
+ net_ratelimit())
Does this really reach 80 columns when unwrapped?
I tried to fix every warning and error noticed by checkpatch.pl, however there are still a few lines longer than 80, just because I couldn't reasonably wrap them.
(there seems to my eye to be a lot of overaggressive wrapping in this
patch, but nevermind)
Yes, that's intentional, we shouldn't exit this loop until everything is unmapped. An i-- would be fine as well. I will put a comment there.
+ netdev_err(vif->dev,
+ "Page still granted! Index: %x\n",
+ i);
+ i = -1;
Should there not be a break here? Otherwise don't we restart the for
loop from 0 again? If that is intentional then a comment would be very
useful.
It shouldn't be guest triggerable. It only means netback really screwed up the accounting of granted pages. There is a BUG right after it, and the kernel should panic here. David suggested to replace this whole stuff with a BUG_ON. One counterargument is that there is a slight chance printing pending_idx can provide some useful info. At least back in the beginning when I tried to fix some basic mistakes it was useful.
@@ -919,11 +873,38 @@ err:
return NULL;
}
+static inline void xenvif_grant_handle_set(struct xenvif *vif,
+ u16 pending_idx,
+ grant_handle_t handle)
+{
+ if (unlikely(vif->grant_tx_handle[pending_idx] !=
+ NETBACK_INVALID_HANDLE)) {
+ netdev_err(vif->dev,
Is this in any way guest triggerable? Needs to be ratelimited in that
case (and arguably even if not?)
Yeah, I was thinking about that, but it's really used here and 2 places in tx_submit, so I didn't bother to do it.
+ "Trying to overwrite active handle! pending_idx: %x\n",
+ pending_idx);
+ BUG();
+ }
+ vif->grant_tx_handle[pending_idx] = handle;
+}
+
+static inline void xenvif_grant_handle_reset(struct xenvif *vif,
+ u16 pending_idx)
+{
+ if (unlikely(vif->grant_tx_handle[pending_idx] ==
+ NETBACK_INVALID_HANDLE)) {
+ netdev_err(vif->dev,
Likewise.
+ "Trying to unmap invalid handle! pending_idx: %x\n",
+ pending_idx);
+ BUG();
+ }
+ vif->grant_tx_handle[pending_idx] = NETBACK_INVALID_HANDLE;
+}
+
@@ -1001,6 +982,17 @@ static void xenvif_fill_frags(struct xenvif *vif, struct sk_buff *skb)
pending_idx = frag_get_pending_idx(frag);
+ /* If this is not the first frag, chain it to the previous*/
+ if (unlikely(prev_pending_idx == INVALID_PENDING_IDX))
+ skb_shinfo(skb)->destructor_arg =
+ &vif->pending_tx_info[pending_idx].callback_struct;
+ else if (likely(pending_idx != prev_pending_idx))
+ vif->pending_tx_info[prev_pending_idx].callback_struct.ctx =
+ &(vif->pending_tx_info[pending_idx].callback_struct);
#define callback_for(vif, pending_idx) .... would make this and a bunch
of other places a lot less verbose IMHO.
Yes, the NAPI instance will use vif->pending_ring[index] only after vif->pending_prod++, so the memory barrier makes sure that we set the element in the ring first and then increase the producer.
+ index = pending_index(vif->pending_prod);
+ vif->pending_ring[index] = pending_idx;
+ /* TX shouldn't use the index before we give it back here */
I hope this comment refers to the pending_prod++ and not the mb(), since
the barrier only guarantees visibility after that point, but not
invisibility before this point.
It comes from the time when xenvif_grant_handle_reset was not a standalone function. Yes, it refers to the check in the beginning of that function, and it should go there.
[...]
+ /* Btw. already unmapped? */
What does this comment mean? Is it a fixme? An indicator that
xenvif_grant_handle_reset is supposed to handle this case or something
else?
I think there was another such comment earlier too.
+ xenvif_grant_handle_reset(vif, pending_idx);
+
+ ret = gnttab_unmap_refs(&tx_unmap_op, NULL,
+ &vif->mmap_pages[pending_idx], 1);
+ BUG_ON(ret);
+
+ xenvif_idx_release(vif, pending_idx, XEN_NETIF_RSP_OKAY);
+}
+
static inline int rx_work_todo(struct xenvif *vif)
{
return !skb_queue_empty(&vif->rx_queue) &&