My recent patch to include/xen/interface/io/netif.h defines a new extra
info type that can be used to pass hash values between backend and guest
frontend.

This patch adds code to xen-netback to use the value in a hash extra
info fragment passed from the guest frontend in a transmit-side
(i.e. netback receive side) packet to set the skb hash accordingly.
Signed-off-by: NPaul Durrant <paul.durrant@citrix.com>
Acked-by: NWei Liu <wei.liu2@citrix.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

My recent patch to include/xen/interface/io/netif.h defines a new extra
info type that can be used to pass hash values between backend and guest
frontend.

This patch adds code to xen-netback to pass hash values calculated for
guest receive-side packets (i.e. netback transmit side) to the frontend.
Signed-off-by: NPaul Durrant <paul.durrant@citrix.com>
Acked-by: NWei Liu <wei.liu2@citrix.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

My recent patch to include/xen/interface/io/netif.h defines a new shared
ring (in addition to the rx and tx rings) for passing control messages
from a VM frontend driver to a backend driver.

A previous patch added the necessary boilerplate for mapping the control
ring from the frontend, should it be created. This patch adds
implementations for each of the defined protocol messages.
Signed-off-by: NPaul Durrant <paul.durrant@citrix.com>
Cc: Wei Liu <wei.liu2@citrix.com>
Acked-by: NWei Liu <wei.liu2@citrix.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

My recent patch to include/xen/interface/io/netif.h defines a new shared
ring (in addition to the rx and tx rings) for passing control messages
from a VM frontend driver to a backend driver.

This patch adds the necessary code to xen-netback to map this new shared
ring, should it be created by a frontend, but does not add implementations
for any of the defined protocol messages. These are added in a subsequent
patch for clarity.
Signed-off-by: NPaul Durrant <paul.durrant@citrix.com>
Acked-by: NWei Liu <wei.liu2@citrix.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Patch 562abd39 "xen-netback: support multiple extra info fragments
passed from frontend" contained a mistake which can result in an in-
correct number of responses being generated when handling errors
encountered when processing packets containing extra info fragments.
This patch fixes the problem.
Signed-off-by: NPaul Durrant <paul.durrant@citrix.com>
Reported-by: NJan Beulich <JBeulich@suse.com>
Cc: Wei Liu <wei.liu2@citrix.com>
Acked-by: NWei Liu <wei.liu2@citrix.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

The code does not currently support a frontend passing multiple extra info
fragments to the backend in a tx request. The xenvif_get_extras() function
handles multiple extra_info fragments but make_tx_response() assumes there
is only ever a single extra info fragment.

This patch modifies xenvif_get_extras() to pass back a count of extra
info fragments, which is then passed to make_tx_response() (after
possibly being stashed in pending_tx_info for deferred responses).
Signed-off-by: NPaul Durrant <paul.durrant@citrix.com>
Cc: Wei Liu <wei.liu2@citrix.com>
Acked-by: NWei Liu <wei.liu2@citrix.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Using the MTU or GSO size to determine the number of required guest Rx
requests for an skb was subtly broken since these value may change at
runtime.

After 1650d545 (xen-netback: always
fully coalesce guest Rx packets) we always fully pack a packet into
its guest Rx slots.  Calculating the number of required slots from the
packet length is then easy.
Signed-off-by: NDavid Vrabel <david.vrabel@citrix.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Instead of open-coding memcpy()s and directly accessing Tx and Rx
requests, use the new RING_COPY_REQUEST() that ensures the local copy
is correct.

This is more than is strictly necessary for guest Rx requests since
only the id and gref fields are used and it is harmless if the
frontend modifies these.

This is part of XSA155.

CC: stable@vger.kernel.org
Reviewed-by: NWei Liu <wei.liu2@citrix.com>
Signed-off-by: NDavid Vrabel <david.vrabel@citrix.com>
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>

The last from guest transmitted request gives no indication about the
minimum amount of credit that the guest might need to send a packet
since the last packet might have been a small one.

Instead allow for the worst case 128 KiB packet.

This is part of XSA155.

CC: stable@vger.kernel.org
Reviewed-by: NWei Liu <wei.liu2@citrix.com>
Signed-off-by: NDavid Vrabel <david.vrabel@citrix.com>
Signed-off-by: NKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>

The PV network protocol is using 4KB page granularity. The goal of this
patch is to allow a Linux using 64KB page granularity working as a
network backend on a non-modified Xen.

It's only necessary to adapt the ring size and break skb data in small
chunk of 4KB. The rest of the code is relying on the grant table code.
Signed-off-by: NJulien Grall <julien.grall@citrix.com>
Reviewed-by: NWei Liu <wei.liu2@citrix.com>
Signed-off-by: NDavid Vrabel <david.vrabel@citrix.com>

The skb doesn't change within the function. Therefore it's only
necessary to check if we need GSO once at the beginning.
Signed-off-by: NJulien Grall <julien.grall@citrix.com>
Acked-by: NWei Liu <wei.liu2@citrix.com>
Signed-off-by: NDavid Vrabel <david.vrabel@citrix.com>

Originally that parameter was always reset to num_online_cpus during
module initialisation, which renders it useless.

The fix is to only set max_queues to num_online_cpus when user has not
provided a value.
Reported-by: NJohnny Strom <johnny.strom@linuxsolutions.fi>
Signed-off-by: NWei Liu <wei.liu2@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>

Commit f48da8b1 (xen-netback: fix
unlimited guest Rx internal queue and carrier flapping) introduced a
regression.

The PV frontend in IPXE only places 4 requests on the guest Rx ring.
Since netback required at least (MAX_SKB_FRAGS + 1) slots, IPXE could
not receive any packets.

a) If GSO is not enabled on the VIF, fewer guest Rx slots are required
   for the largest possible packet.  Calculate the required slots
   based on the maximum GSO size or the MTU.

   This calculation of the number of required slots relies on
   1650d545 (xen-netback: always fully coalesce guest Rx packets)
   which present in 4.0-rc1 and later.

b) Reduce the Rx stall detection to checking for at least one
   available Rx request.  This is fine since we're predominately
   concerned with detecting interfaces which are down and thus have
   zero available 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>

Based on include/xen/mm.h [1], Linux is mistakenly using MFN when GFN
is meant, I suspect this is because the first support for Xen was for
PV. This resulted in some misimplementation of helpers on ARM and
confused developers about the expected behavior.

For instance, with pfn_to_mfn, we expect to get an MFN based on the name.
Although, if we look at the implementation on x86, it's returning a GFN.

For clarity and avoid new confusion, replace any reference to mfn with
gfn in any helpers used by PV drivers. The x86 code will still keep some
reference of pfn_to_mfn which may be used by all kind of guests
No changes as been made in the hypercall field, even
though they may be invalid, in order to keep the same as the defintion
in xen repo.

Note that page_to_mfn has been renamed to xen_page_to_gfn to avoid a
name to close to the KVM function gfn_to_page.

Take also the opportunity to simplify simple construction such
as pfn_to_mfn(page_to_pfn(page)) into xen_page_to_gfn. More complex clean up
will come in follow-up patches.

[1] http://xenbits.xen.org/gitweb/?p=xen.git;a=commitdiff;h=e758ed14f390342513405dd766e874934573e6cbSigned-off-by: NJulien Grall <julien.grall@citrix.com>
Reviewed-by: NStefano Stabellini <stefano.stabellini@eu.citrix.com>
Acked-by: NDmitry Torokhov <dmitry.torokhov@gmail.com>
Acked-by: NWei Liu <wei.liu2@citrix.com>
Signed-off-by: NDavid Vrabel <david.vrabel@citrix.com>

Xen's PV network protocol includes messages to add/remove ethernet
multicast addresses to/from a filter list in the backend. This allows
the frontend to request the backend only forward multicast packets
which are of interest thus preventing unnecessary noise on the shared
ring.

The canonical netif header in git://xenbits.xen.org/xen.git specifies
the message format (two more XEN_NETIF_EXTRA_TYPEs) so the minimal
necessary changes have been pulled into include/xen/interface/io/netif.h.

To prevent the frontend from extending the multicast filter list
arbitrarily a limit (XEN_NETBK_MCAST_MAX) has been set to 64 entries.
This limit is not specified by the protocol and so may change in future.
If the limit is reached then the next XEN_NETIF_EXTRA_TYPE_MCAST_ADD
sent by the frontend will be failed with NETIF_RSP_ERROR.
Signed-off-by: NPaul Durrant <paul.durrant@citrix.com>
Cc: Ian Campbell <ian.campbell@citrix.com>
Cc: Wei Liu <wei.liu2@citrix.com>
Acked-by: NWei Liu <wei.liu2@citrix.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Waking the dealloc thread before decrementing inflight_packets is racy
because it means the thread may go to sleep before inflight_packets is
decremented. If kthread_stop() has already been called, the dealloc
thread may wait forever with nothing to wake it. Instead, wake the
thread only after decrementing inflight_packets.
Signed-off-by: NRoss Lagerwall <ross.lagerwall@citrix.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Determine if a fraglist is needed in the tx path, and allocate it if
necessary before setting up the copy and map operations.
Otherwise, undoing the copy and map operations is tricky.

This fixes a use-after-free: if allocating the fraglist failed, the copy
and map operations that had been set up were still executed, writing
over the data area of a freed skb.
Signed-off-by: NRoss Lagerwall <ross.lagerwall@citrix.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

The > should be >=.  I also added spaces around the '-' operations so
the code is a little more consistent and matches the condition better.

Fixes: f53c3fe8 ('xen-netback: Introduce TX grant mapping')
Signed-off-by: NDan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Append 0x to all %x in order to avoid while reading when there is other
decimal value in the log.

Also replace some of the hexadecimal print to decimal to uniformize the
format with netfront.
Signed-off-by: NJulien Grall <julien.grall@citrix.com>
Cc: Wei Liu <wei.liu2@citrix.com>
Cc: Ian Campbell <ian.campbell@citrix.com>
Cc: netdev@vger.kernel.org
Acked-by: NIan Campbell <ian.campbell@citrix.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

The variables old_req_cons and ring_slots_used are assigned but never
used since commit 1650d545 "xen-netback:
always fully coalesce guest Rx packets".
Signed-off-by: NJulien Grall <julien.grall@citrix.com>
Acked-by: NWei Liu <wei.liu2@citrix.com>
Cc: Ian Campbell <ian.campbell@citrix.com>
Cc: netdev@vger.kernel.org
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Using xen/page.h will be necessary later for using common xen page
helpers.

As xen/page.h already include asm/xen/page.h, always use the later.
Signed-off-by: NJulien Grall <julien.grall@citrix.com>
Reviewed-by: NDavid Vrabel <david.vrabel@citrix.com>
Cc: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Cc: Ian Campbell <ian.campbell@citrix.com>
Cc: Wei Liu <wei.liu2@citrix.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: netdev@vger.kernel.org
Signed-off-by: NDavid Vrabel <david.vrabel@citrix.com>

drivers/net/xen-netback/netback.c: In function ‘xenvif_tx_build_gops’:
drivers/net/xen-netback/netback.c:1253:8: warning: format ‘%lu’ expects argument of type ‘long unsigned int’, but argument 5 has type ‘int’ [-Wformat=]
        (txreq.offset&~PAGE_MASK) + txreq.size);
        ^

PAGE_MASK's type can vary by arch, so a cast is needed.
Signed-off-by: NIan Campbell <ian.campbell@citrix.com>
----
v2: Cast to unsigned long, since PAGE_MASK can vary by arch.
Acked-by: NWei Liu <wei.liu2@citrix.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

The variable separate_tx_rx_irq is bool type so assigning true
instead of 1.
Signed-off-by: NShailendra Verma <shailendra.capricorn@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Originally Xen PV drivers only use single-page ring to pass along
information. This might limit the throughput between frontend and
backend.

The patch extends Xenbus driver to support multi-page ring, which in
general should improve throughput if ring is the bottleneck. Changes to
various frontend / backend to adapt to the new interface are also
included.

Affected Xen drivers:
* blkfront/back
* netfront/back
* pcifront/back
* scsifront/back
* vtpmfront

The interface is documented, as before, in xenbus_client.c.
Signed-off-by: NWei Liu <wei.liu2@citrix.com>
Signed-off-by: NPaul Durrant <paul.durrant@citrix.com>
Signed-off-by: NBob Liu <bob.liu@oracle.com>
Cc: Konrad Wilk <konrad.wilk@oracle.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: NDavid Vrabel <david.vrabel@citrix.com>

With the current netback, the bandwidth limiter's parameters are only
settable during vif setup time.  This patch register a watch on them, and
thus makes them runtime changeable.

When the watch fires, the timer is reset.  The timer's mutex is used for
fencing the change.

Cc: Anthony Liguori <aliguori@amazon.com>
Signed-off-by: NImre Palik <imrep@amazon.de>
Acked-by: NWei Liu <wei.liu2@citrix.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

This fixes a performance regression introduced by
7fbb9d84 (xen-netback: release pending
index before pushing Tx responses)

Moving the notify outside of the spin locks means it can be delayed a
long time (if the dealloc thread is descheduled or there is an
interrupt or softirq).
Signed-off-by: NDavid Vrabel <david.vrabel@citrix.com>
Reviewed-by: NZoltan Kiss <zoltan.kiss@linaro.org>
Acked-by: NWei Liu <wei.liu2@citrix.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

When handling a from-guest frag list, xenvif_handle_frag_list()
replaces the frags before calling the destructor to clean up the
original (foreign) frags.  Whilst this is safe (the destructor doesn't
actually use the frags), it looks odd.

Reorder the function to be less confusing.
Signed-off-by: NDavid Vrabel <david.vrabel@citrix.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Every time a VIF is destroyed up to 256 pages may be leaked if packets
with more than MAX_SKB_FRAGS frags were transmitted from the guest.
Even worse, if another user of ballooned pages allocated one of these
ballooned pages it would not handle the unexpectedly >1 page count
(e.g., gntdev would deadlock when unmapping a grant because the page
count would never reach 1).

When handling a from-guest skb with a frag list, unref the frags
before releasing them so they are freed correctly when the VIF is
destroyed.
Signed-off-by: NDavid Vrabel <david.vrabel@citrix.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

If the pending indexes are released /after/ pushing the Tx response
then a stale pending index may be used if a new Tx request is
immediately pushed by the frontend.  The may cause various WARNINGs or
BUGs if the stale pending index is actually still in use.

Fix this by releasing the pending index before pushing the Tx
response.

The full barrier for the pending ring update is not required since the
the Tx response push already has a suitable write barrier.
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>

After commit e9d8b2c2 (xen-netback:
disable rogue vif in kthread context), a fatal (protocol) error would
leave the guest Rx thread spinning, wasting CPU time.  Commit
ecf08d2d (xen-netback: reintroduce
guest Rx stall detection) made this even worse by removing a
cond_resched() from this path.

Since a fatal error is non-recoverable, just allow the guest Rx thread
to exit.  This requires taking additional refs to the task so the
thread exiting early is handled safely.
Signed-off-by: NDavid Vrabel <david.vrabel@citrix.com>
Reported-by: NJulien Grall <julien.grall@linaro.org>
Tested-by: NJulien Grall <julien.grall@linaro.org>
Acked-by: NWei Liu <wei.liu2@citrix.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Use the foreign page flag in netback to get the domid and grant ref
needed for the grant copy.  This signficiantly simplifies the netback
code and makes netback work with foreign pages from other backends
(e.g., blkback).

This allows blkback to use iSCSI disks provided by domUs running on
the same host.
Signed-off-by: NJennifer Herbert <jennifer.herbert@citrix.com>
Acked-by: NIan Campbell <ian.campbell@citrix.com>
Acked-by: NDavid S. Miller <davem@davemloft.net>
Signed-off-by: NDavid Vrabel <david.vrabel@citrix.com>

Ballooned pages are always used for grant maps which means the
original frame does not need to be saved in page->index nor restored
after the grant unmap.

This allows the workaround in netback for the conflicting use of the
(unionized) page->index and page->pfmemalloc to be removed.
Signed-off-by: NJennifer Herbert <jennifer.herbert@citrix.com>
Reviewed-by: NStefano Stabellini <stefano.stabellini@eu.citrix.com>
Signed-off-by: NDavid Vrabel <david.vrabel@citrix.com>

Always fully coalesce guest Rx packets into the minimum number of ring
slots.  Reducing the number of slots per packet has significant
performance benefits when receiving off-host traffic.

Results from XenServer's performance benchmarks:

                         Baseline    Full coalesce
Interhost VM receive      7.2 Gb/s   11 Gb/s
Interhost aggregate      24 Gb/s     24 Gb/s
Intrahost single stream  14 Gb/s     14 Gb/s
Intrahost aggregate      34 Gb/s     34 Gb/s

However, this can increase the number of grant ops per packet which
decreases performance of backend (dom0) to VM traffic (by ~10%)
/unless/ grant copy has been optimized for adjacent ops with the same
source or destination (see "grant-table: defer releasing pages
acquired in a grant copy"[1] expected in Xen 4.6).

[1] http://lists.xen.org/archives/html/xen-devel/2015-01/msg01118.htmlSigned-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>

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>