Commit bc96f648 (xen-netback: make
feature-rx-notify mandatory) incorrectly assumed that there were no
frontends in use that did not support this feature.  But the frontend
driver in MiniOS does not and since this is used by (qemu) stubdoms,
these stopped working.

Netback sort of works as-is in this mode except:

- If there are no Rx requests and the internal Rx queue fills, only
  the drain timeout will wake the thread.  The default drain timeout
  of 10 s would give unacceptable pauses.

- If an Rx stall was detected and the internal Rx queue is drained,
  then the Rx thread would never wake.

Handle these two cases (when feature-rx-notify is disabled) by:

- Reducing the drain timeout to 30 ms.

- Disabling Rx stall detection.
Reported-by: NJohn <jw@nuclearfallout.net>
Tested-by: NJohn <jw@nuclearfallout.net>
Signed-off-by: NDavid Vrabel <david.vrabel@citrix.com>
Reviewed-by: NWei Liu <wei.liu2@citrix.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Unconditionally pulling 128 bytes into the linear area is not required
for:

- security: Every protocol demux starts with pskb_may_pull() to pull
  frag data into the linear area, if necessary, before looking at
  headers.

- performance: Netback has already grant copied up-to 128 bytes from
  the first slot of a packet into the linear area. The first slot
  normally contain all the IPv4/IPv6 and TCP/UDP headers.

The unconditional pull would often copy frag data unnecessarily.  This
is a performance problem when running on a version of Xen where grant
unmap avoids TLB flushes for pages which are not accessed.  TLB
flushes can now be avoided for > 99% of unmaps (it was 0% before).

Grant unmap TLB flush avoidance will be available in a future version
of Xen (probably 4.6).
Signed-off-by: NMalcolm Crossley <malcolm.crossley@citrix.com>
Signed-off-by: NDavid Vrabel <david.vrabel@citrix.com>
Acked-by: NIan Campbell <ian.campbell@citrix.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

This flag is unnecessary, it came from some old code.
Suggested-by: NEric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: NZoltan Kiss <zoltan.kiss@linaro.org>
Signed-off-by: NDavid Vrabel <david.vrabel@citrix.com>
Acked-by: NWei Liu <wei.liu2@citrix.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

If a frontend not receiving packets it is useful to detect this and
turn off the carrier so packets are dropped early instead of being
queued and drained when they expire.

A to-guest queue is stalled if it doesn't have enough free slots for a
an extended period of time (default 60 s).

If at least one queue is stalled, the carrier is turned off (in the
expectation that the other queues will soon stall as well).  The
carrier is only turned on once all queues are ready.

When the frontend connects, all the queues start in the stalled state
and only become ready once the frontend queues enough Rx requests.
Signed-off-by: NDavid Vrabel <david.vrabel@citrix.com>
Reviewed-by: NWei Liu <wei.liu2@citrix.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Netback needs to discard old to-guest skb's (guest Rx queue drain) and
it needs detect guest Rx stalls (to disable the carrier so packets are
discarded earlier), but the current implementation is very broken.

1. The check in hard_start_xmit of the slot availability did not
   consider the number of packets that were already in the guest Rx
   queue.  This could allow the queue to grow without bound.

   The guest stops consuming packets and the ring was allowed to fill
   leaving S slot free.  Netback queues a packet requiring more than S
   slots (ensuring that the ring stays with S slots free).  Netback
   queue indefinately packets provided that then require S or fewer
   slots.

2. The Rx stall detection is not triggered in this case since the
   (host) Tx queue is not stopped.

3. If the Tx queue is stopped and a guest Rx interrupt occurs, netback
   will consider this an Rx purge event which may result in it taking
   the carrier down unnecessarily.  It also considers a queue with
   only 1 slot free as unstalled (even though the next packet might
   not fit in this).

The internal guest Rx queue is limited by a byte length (to 512 Kib,
enough for half the ring).  The (host) Tx queue is stopped and started
based on this limit.  This sets an upper bound on the amount of memory
used by packets on the internal queue.

This allows the estimatation of the number of slots for an skb to be
removed (it wasn't a very good estimate anyway).  Instead, the guest
Rx thread just waits for enough free slots for a maximum sized packet.

skbs queued on the internal queue have an 'expires' time (set to the
current time plus the drain timeout).  The guest Rx thread will detect
when the skb at the head of the queue has expired and discard expired
skbs.  This sets a clear upper bound on the length of time an skb can
be queued for.  For a guest being destroyed the maximum time needed to
wait for all the packets it sent to be dropped is still the drain
timeout (10 s) since it will not be sending new packets.

Rx stall detection is reintroduced in a later commit.
Signed-off-by: NDavid Vrabel <david.vrabel@citrix.com>
Reviewed-by: NWei Liu <wei.liu2@citrix.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Reference count the number of packets in host stack, so that we don't
stop the deallocation thread too early. If not, we can end up with
xenvif_free permanently waiting for deallocation thread to unmap grefs.
Reported-by: NThomas Leonard <talex5@gmail.com>
Signed-off-by: NWei Liu <wei.liu2@citrix.com>
Cc: Ian Campbell <ian.campbell@citrix.com>
Cc: Zoltan Kiss <zoltan.kiss@citrix.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

In the patch called "xen-netback: Turn off the carrier if the guest is not able
to receive" new branches were introduced to this if statement, risking that a
queue with non-zero id can reenable the disabled interface.
Signed-off-by: NZoltan Kiss <zoltan.kiss@citrix.com>
Signed-off-by: NDavid Vrabel <david.vrabel@citrix.com>
Cc: netdev@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: xen-devel@lists.xenproject.org
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Currently when the guest is not able to receive more packets, qdisc layer starts
a timer, and when it goes off, qdisc is started again to deliver a packet again.
This is a very slow way to drain the queues, consumes unnecessary resources and
slows down other guests shutdown.
This patch change the behaviour by turning the carrier off when that timer
fires, so all the packets are freed up which were stucked waiting for that vif.
Instead of the rx_queue_purge bool it uses the VIF_STATUS_RX_PURGE_EVENT bit to
signal the thread that either the timeout happened or an RX interrupt arrived,
so the thread can check what it should do. It also disables NAPI, so the guest
can't transmit, but leaves the interrupts on, so it can resurrect.
Only the queues which brought down the interface can enable it again, the bit
QUEUE_STATUS_RX_STALLED makes sure of that.
Signed-off-by: NZoltan Kiss <zoltan.kiss@citrix.com>
Signed-off-by: NDavid Vrabel <david.vrabel@citrix.com>
Cc: netdev@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: xen-devel@lists.xenproject.org
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

This patch introduces a new state bit VIF_STATUS_CONNECTED to track whether the
vif is in a connected state. Using carrier will not work with the next patch
in this series, which aims to turn the carrier temporarily off if the guest
doesn't seem to be able to receive packets.
Signed-off-by: NZoltan Kiss <zoltan.kiss@citrix.com>
Signed-off-by: NDavid Vrabel <david.vrabel@citrix.com>
Cc: netdev@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: xen-devel@lists.xenproject.org

v2:
- rename the bitshift type to "enum state_bit_shift" here, not in the next patch
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Due to this pointer is increased prematurely, the error log contains rubbish.
Signed-off-by: NZoltan Kiss <zoltan.kiss@citrix.com>
Reported-by: NArmin Zentai <armin.zentai@ezit.hu>
Cc: netdev@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: xen-devel@lists.xenproject.org
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

This patch makes this function aware that the first frag and the header might
share the same ring slot. That could happen if the first slot is bigger than
PKT_PROT_LEN. Due to this the error path might release that slot twice or never,
depending on the error scenario.
xenvif_idx_release is also removed from xenvif_idx_unmap, and called separately.
Signed-off-by: NZoltan Kiss <zoltan.kiss@citrix.com>
Reported-by: NArmin Zentai <armin.zentai@ezit.hu>
Cc: netdev@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: xen-devel@lists.xenproject.org
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

When the grant operations failed, the skb is freed up eventually, and it tries
to release the frags, if there is any. For the main skb nr_frags is set to 0 to
avoid this, but on the frag_list it iterates through the frags array, and tries
to call put_page on the page pointer which contains garbage at that time.
Signed-off-by: NZoltan Kiss <zoltan.kiss@citrix.com>
Reported-by: NArmin Zentai <armin.zentai@ezit.hu>
Cc: netdev@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: xen-devel@lists.xenproject.org
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

The error handling for skb's with frag_list was completely wrong, it caused
double unmap attempts to happen if the error was on the first skb. Move it to
the right place in the loop.
Signed-off-by: NZoltan Kiss <zoltan.kiss@citrix.com>
Reported-by: NArmin Zentai <armin.zentai@ezit.hu>
Cc: netdev@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: xen-devel@lists.xenproject.org
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

This patch adds debugfs capabilities to netback. There used to be a similar
patch floating around for classic kernel, but it used procfs. It is based on a
very similar blkback patch.
It creates xen-netback/[vifname]/io_ring_q[queueno] files, reading them output
various ring variables etc. Writing "kick" into it imitates an interrupt
happened, it can be useful to check whether the ring is just stalled due to a
missed interrupt.
Signed-off-by: NZoltan Kiss <zoltan.kiss@citrix.com>
Cc: netdev@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: xen-devel@lists.xenproject.org
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

A recent commit (a02eb4 "xen-netback: worse-case estimate in xenvif_rx_action is
underestimating") capped the slot estimation to MAX_SKB_FRAGS, but that triggers
the next BUG_ON a few lines down, as the packet consumes more slots than
estimated.
This patch introduces full_coalesce on the skb callback buffer, which is used in
start_new_rx_buffer() to decide whether netback needs coalescing more
aggresively. By doing that, no packet should need more than
(XEN_NETIF_MAX_TX_SIZE + 1) / PAGE_SIZE data slots (excluding the optional GSO
slot, it doesn't carry data, therefore irrelevant in this case), as the provided
buffers are fully utilized.
Signed-off-by: NZoltan Kiss <zoltan.kiss@citrix.com>
Cc: Paul Durrant <paul.durrant@citrix.com>
Cc: Wei Liu <wei.liu2@citrix.com>
Cc: Ian Campbell <ian.campbell@citrix.com>
Cc: David Vrabel <david.vrabel@citrix.com>
Reviewed-by: NPaul Durrant <paul.durrant@gmail.com>
Acked-by: NWei Liu <wei.liu2@citrix.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Builds on the refactoring of the previous patch to implement multiple
queues between xen-netfront and xen-netback.

Writes the maximum supported number of queues into XenStore, and reads
the values written by the frontend to determine how many queues to use.

Ring references and event channels are read from XenStore on a per-queue
basis and rings are connected accordingly.

Also adds code to handle the cleanup of any already initialised queues
if the initialisation of a subsequent queue fails.
Signed-off-by: NAndrew J. Bennieston <andrew.bennieston@citrix.com>
Acked-by: NWei Liu <wei.liu2@citrix.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

In preparation for multi-queue support in xen-netback, move the
queue-specific data from struct xenvif into struct xenvif_queue, and
update the rest of the code to use this.

Also adds loops over queues where appropriate, even though only one is
configured at this point, and uses alloc_netdev_mq() and the
corresponding multi-queue netif wake/start/stop functions in preparation
for multiple active queues.

Finally, implements a trivial queue selection function suitable for
ndo_select_queue, which simply returns 0 for a single queue and uses
skb_get_hash() to compute the queue index otherwise.
Signed-off-by: NAndrew J. Bennieston <andrew.bennieston@citrix.com>
Signed-off-by: NWei Liu <wei.liu2@citrix.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

When the NAPI budget was not all used, xenvif_poll() would call
napi_complete() /after/ enabling the interrupt.  This resulted in a
race between the napi_complete() and the napi_schedule() in the
interrupt handler.  The use of local_irq_save/restore() avoided by
race iff the handler is running on the same CPU but not if it was
running on a different CPU.

Fix this properly by calling napi_complete() before reenabling
interrupts (in the xenvif_napi_schedule_or_enable_irq() call).
Signed-off-by: NDavid Vrabel <david.vrabel@citrix.com>
Acked-by: NWei Liu <wei.liu2@citrix.com>
Acked-by: NIan Campbell <ian.campbell@citrix.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

The original series for reintroducing grant mapping for netback had a patch [1]
to handle receiving of packets from an another VIF. Grant copy on the receiving
side needs the grant ref of the page to set up the op.
The original patch assumed (wrongly) that the frags array haven't changed. In
the case reported by Sander, the sending guest sent a packet where the linear
buffer and the first frag were under PKT_PROT_LEN (=128) bytes.
xenvif_tx_submit() then pulled up the linear area to 128 bytes, and ditched the
first frag. The receiving side had an off-by-one problem when gathered the grant
refs.
This patch fixes that by checking whether the actual frag's page pointer is the
same as the page in the original frag list. It can handle any kind of changes on
the original frags array, like:
- removing granted frags from the array at any point
- adding local pages to the frags list anywhere
- reordering the frags
It's optimized to the most common case, when there is 1:1 relation between the
frags and the list, plus works optimal when frags are removed from the end or
the beginning.

[1]: 3e2234: xen-netback: Handle foreign mapped pages on the guest RX path
Reported-by: NSander Eikelenboom <linux@eikelenboom.it>
Signed-off-by: NZoltan Kiss <zoltan.kiss@citrix.com>
Acked-by: NIan Campbell <ian.campbell@citrix.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

There is a "%" after pending_idx instead of ":".
Signed-off-by: NZoltan Kiss <zoltan.kiss@citrix.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

An old inefficiency of the TX path that we are grant mapping the first slot,
and then copy the header part to the linear area. Instead, doing a grant copy
for that header straight on is more reasonable. Especially because there are
ongoing efforts to make Xen avoiding TLB flush after unmap when the page were
not touched in Dom0. In the original way the memcpy ruined that.
The key changes:
- the vif has a tx_copy_ops array again
- xenvif_tx_build_gops sets up the grant copy operations
- we don't have to figure out whether the header and first frag are on the same
  grant mapped page or not
Note, we only grant copy PKT_PROT_LEN bytes from the first slot, the rest (if
any) will be on the first frag, which is grant mapped. If the first slot is
smaller than PKT_PROT_LEN, then we grant copy that, and later __pskb_pull_tail
will pull more from the frags (if any)
Signed-off-by: NZoltan Kiss <zoltan.kiss@citrix.com>
Reviewed-by: NPaul Durrant <paul.durrant@citrix.com>
Acked-by: NIan Campbell <ian.campbell@citrix.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Rename identifiers to state explicitly that they refer to map ops.
Signed-off-by: NZoltan Kiss <zoltan.kiss@citrix.com>
Reviewed-by: NPaul Durrant <paul.durrant@citrix.com>
Acked-by: NIan Campbell <ian.campbell@citrix.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

When netback discovers frontend is sending malformed packet it will
disables the interface which serves that frontend.

However disabling a network interface involving taking a mutex which
cannot be done in softirq context, so we need to defer this process to
kthread context.

This patch does the following:
1. introduce a flag to indicate the interface is disabled.
2. check that flag in TX path, don't do any work if it's true.
3. check that flag in RX path, turn off that interface if it's true.

The reason to disable it in RX path is because RX uses kthread. After
this change the behavior of netback is still consistent -- it won't do
any TX work for a rogue frontend, and the interface will be eventually
turned off.

Also change a "continue" to "break" after xenvif_fatal_tx_err, as it
doesn't make sense to continue processing packets if frontend is rogue.

This is a fix for XSA-90.
Reported-by: NTörök Edwin <edwin@etorok.net>
Signed-off-by: NWei Liu <wei.liu2@citrix.com>
Cc: Ian Campbell <ian.campbell@citrix.com>
Reviewed-by: NDavid Vrabel <david.vrabel@citrix.com>
Acked-by: NIan Campbell <ian.campbell@citrix.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

The BUG_ON to catch ring overflow in xenvif_rx_action() makes the assumption
that meta_slots_used == ring slots used. This is not necessarily the case
for GSO packets, because the non-prefix GSO protocol consumes one more ring
slot than meta-slot for the 'extra_info'. This patch changes the test to
actually check ring slots.
Signed-off-by: NPaul Durrant <paul.durrant@citrix.com>
Cc: Ian Campbell <ian.campbell@citrix.com>
Cc: Wei Liu <wei.liu2@citrix.com>
Cc: Sander Eikelenboom <linux@eikelenboom.it>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

The worse-case estimate for skb ring slot usage in xenvif_rx_action()
fails to take fragment page_offset into account. The page_offset does,
however, affect the number of times the fragmentation code calls
start_new_rx_buffer() (i.e. consume another slot) and the worse-case
should assume that will always return true. This patch adds the page_offset
into the DIV_ROUND_UP for each frag.

Unfortunately some frontends aggressively limit the number of requests
they post into the shared ring so to avoid an estimate that is 'too'
pessimal it is capped at MAX_SKB_FRAGS.
Signed-off-by: NPaul Durrant <paul.durrant@citrix.com>
Cc: Ian Campbell <ian.campbell@citrix.com>
Cc: Wei Liu <wei.liu2@citrix.com>
Cc: Sander Eikelenboom <linux@eikelenboom.it>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

This patch removes a test in start_new_rx_buffer() that checks whether
a copy operation is less than MAX_BUFFER_OFFSET in length, since
MAX_BUFFER_OFFSET is defined to be PAGE_SIZE and the only caller of
start_new_rx_buffer() already limits copy operations to PAGE_SIZE or less.
Signed-off-by: NPaul Durrant <paul.durrant@citrix.com>
Cc: Ian Campbell <ian.campbell@citrix.com>
Cc: Wei Liu <wei.liu2@citrix.com>
Cc: Sander Eikelenboom <linux@eikelenboom.it>
Reported-By: NSander Eikelenboom <linux@eikelenboom.it>
Tested-By: NSander Eikelenboom <linux@eikelenboom.it>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Ian made some late comments about the grant mapping series, I incorporated the
functional outcomes into this patch:

- use callback_param macro to shorten access to pending_tx_info in
  xenvif_fill_frags() and xenvif_tx_submit()
- print an error message in xenvif_idx_unmap() before panic
Signed-off-by: NZoltan Kiss <zoltan.kiss@citrix.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Ian made some late comments about the grant mapping series, I incorporated the
non-functional outcomes into this patch:

- typo fixes in a comment of xenvif_free(), and add another one there as well
- typo fix for comment of rx_drain_timeout_msecs
- remove stale comment before calling xenvif_grant_handle_reset()
Signed-off-by: NZoltan Kiss <zoltan.kiss@citrix.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Since the early days TX stops if there isn't enough free pending slots to
consume a maximum sized (slot-wise) packet. Probably the reason for that is to
avoid the case when we don't have enough free pending slot in the ring to finish
the packet. But if we make sure that the pending ring has the same size as the
shared ring, that shouldn't really happen. The frontend can only post packets
which fit the to the free space of the shared ring. If it doesn't, the frontend
has to stop, as it can only increase the req_prod when the whole packet fits
onto the ring.
This patch avoid using this checking, makes sure the 2 ring has the same size,
and remove a checking from the callback. As now we don't stop the NAPI instance
on this condition, we don't have to wake it up if we free pending slots up.
Signed-off-by: NZoltan Kiss <zoltan.kiss@citrix.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

This fixes:

drivers/net/xen-netback/netback.c: In function ‘xenvif_tx_dealloc_action’:
drivers/net/xen-netback/netback.c:1573:8: warning: format ‘%x’ expects argument of type ‘unsigned int’, but argument 3 has type ‘long int’ [-Wformat=]
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

This reverts commit e9275f5e. This commit is the
last in the netback grant mapping series, and it tries to do more aggressive
aggreagtion of unmap operations. However practical use showed almost no
positive effect, whilst with certain frontends it causes significant performance
regression.
Signed-off-by: NZoltan Kiss <zoltan.kiss@citrix.com>
Acked-by: NIan Campbell <ian.campbell@citrix.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Current netback uses gso_type to check whether the skb contains
gso offload, and this is wrong. Gso_size is the right one to
check gso existence, and gso_type is only used to check gso type.

Some skbs contains nonzero gso_type and zero gso_size, current
netback would treat these skbs as gso and create wrong response
for this. This also causes ssh failure to domu from other server.

V2: use skb_is_gso function as Paul Durrant suggested
Signed-off-by: NAnnie Li <annie.li@oracle.com>
Acked-by: NWei Liu <wei.liu2@citrix.com>
Reviewed-by: NPaul Durrant <paul.durrant@citrix.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Unmapping causes TLB flushing, therefore we should make it in the largest
possible batches. However we shouldn't starve the guest for too long. So if
the guest has space for at least two big packets and we don't have at least a
quarter ring to unmap, delay it for at most 1 milisec.
Signed-off-by: NZoltan Kiss <zoltan.kiss@citrix.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

A malicious or buggy guest can leave its queue filled indefinitely, in which
case qdisc start to queue packets for that VIF. If those packets came from an
another guest, it can block its slots and prevent shutdown. To avoid that, we
make sure the queue is drained in every 10 seconds.
The QDisc queue in worst case takes 3 round to flush usually.
Signed-off-by: NZoltan Kiss <zoltan.kiss@citrix.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Xen network protocol had implicit dependency on MAX_SKB_FRAGS. Netback has to
handle guests sending up to XEN_NETBK_LEGACY_SLOTS_MAX slots. To achieve that:
- create a new skb
- map the leftover slots to its frags (no linear buffer here!)
- chain it to the previous through skb_shinfo(skb)->frag_list
- map them
- copy and coalesce the frags into a brand new one and send it to the stack
- unmap the 2 old skb's pages

It's also introduces new stat counters, which help determine how often the guest
sends a packet with more than MAX_SKB_FRAGS frags.

NOTE: if bisect brought you here, you should apply the series up until
"xen-netback: Timeout packets in RX path", otherwise malicious guests can block
other guests by not releasing their sent packets.
Signed-off-by: NZoltan Kiss <zoltan.kiss@citrix.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

These counters help determine how often the buffers had to be copied. Also
they help find out if packets are leaked, as if "sent != success + fail",
there are probably packets never freed up properly.

NOTE: if bisect brought you here, you should apply the series up until
"xen-netback: Timeout packets in RX path", otherwise Windows guests can't work
properly and malicious guests can block other guests by not releasing their sent
packets.
Signed-off-by: NZoltan Kiss <zoltan.kiss@citrix.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

These became obsolete with grant mapping. I've left intentionally the
indentations in this way, to improve readability of previous patches.

NOTE: if bisect brought you here, you should apply the series up until
"xen-netback: Timeout packets in RX path", otherwise Windows guests can't work
properly and malicious guests can block other guests by not releasing their sent
packets.
Signed-off-by: NZoltan Kiss <zoltan.kiss@citrix.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

This patch introduces grant mapping on netback TX path. It replaces grant copy
operations, ditching grant copy coalescing along the way. Another solution for
copy coalescing is introduced in "xen-netback: Handle guests with too many
frags", older guests and Windows can broke before that patch applies.
There is a callback (xenvif_zerocopy_callback) from core stack to release the
slots back to the guests when kfree_skb or skb_orphan_frags called. It feeds a
separate dealloc thread, as scheduling NAPI instance from there is inefficient,
therefore we can't do dealloc from the instance.
Signed-off-by: NZoltan Kiss <zoltan.kiss@citrix.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

RX path need to know if the SKB fragments are stored on pages from another
domain.
Logically this patch should be after introducing the grant mapping itself, as
it makes sense only after that. But to keep bisectability, I moved it here. It
shouldn't change any functionality here. xenvif_zerocopy_callback and
ubuf_to_vif are just stubs here, they will be introduced properly later on.
Signed-off-by: NZoltan Kiss <zoltan.kiss@citrix.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

This patch contains a few bits of refactoring before introducing the grant
mapping changes:
- introducing xenvif_tx_pending_slots_available(), as this is used several
  times, and will be used more often
- rename the thread to vifX.Y-guest-rx, to signify it does RX work from the
  guest point of view
Signed-off-by: NZoltan Kiss <zoltan.kiss@citrix.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>