[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH net-next v7 4/9] xen-netback: Introduce TX grant mapping
On 13/03/14 10:33, Ian Campbell 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 threadOn Thu, 2014-03-06 at 21:48 +0000, Zoltan Kiss wrote:@@ -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) && _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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