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[PATCH 3.12 07/98] xen-netback: don't use last request to determine minimum Tx credit

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From: David Vrabel <david.vrabel@citrix.com>

3.12-stable review patch.  If anyone has any objections, please let me know.

===============

commit 0f589967a73f1f30ab4ac4dd9ce0bb399b4d6357 upstream.

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.

Reviewed-by: Wei Liu <wei.liu2@citrix.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
 drivers/net/xen-netback/netback.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
index a1186533cee8..d4a1db9fb224 100644
--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c
@@ -695,9 +695,7 @@ static void tx_add_credit(struct xenvif *vif)
 	 * Allow a burst big enough to transmit a jumbo packet of up to 128kB.
 	 * Otherwise the interface can seize up due to insufficient credit.
 	 */
-	max_burst = RING_GET_REQUEST(&vif->tx, vif->tx.req_cons)->size;
-	max_burst = min(max_burst, 131072UL);
-	max_burst = max(max_burst, vif->credit_bytes);
+	max_burst = max(131072UL, vif->credit_bytes);
 
 	/* Take care that adding a new chunk of credit doesn't wrap to zero. */
 	max_credit = vif->remaining_credit + vif->credit_bytes;
-- 
2.8.1

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[PATCH 3.12 00/98] 3.12.58-stable review Jiri Slaby <jslaby@suse.cz> - 2016-04-11 15:30 +0200
  Re: [PATCH 3.12 00/98] 3.12.58-stable review Guenter Roeck <linux@roeck-us.net> - 2016-04-11 15:40 +0200
    Re: [PATCH 3.12 00/98] 3.12.58-stable review Jiri Slaby <jslaby@suse.cz> - 2016-04-14 10:30 +0200
  [PATCH 3.12 01/98] ipr: Fix out-of-bounds null overwrite Jiri Slaby <jslaby@suse.cz> - 2016-04-11 16:10 +0200
    [PATCH 3.12 18/98] ALSA: rawmidi: Make snd_rawmidi_transmit() race-free Jiri Slaby <jslaby@suse.cz> - 2016-04-11 16:10 +0200
    [PATCH 3.12 23/98] KVM: SVM: add rdmsr support for AMD event registers Jiri Slaby <jslaby@suse.cz> - 2016-04-11 16:10 +0200
    [PATCH 3.12 08/98] xen-netback: use RING_COPY_REQUEST() throughout Jiri Slaby <jslaby@suse.cz> - 2016-04-11 16:10 +0200
    [PATCH 3.12 07/98] xen-netback: don't use last request to determine minimum Tx credit Jiri Slaby <jslaby@suse.cz> - 2016-04-11 16:10 +0200
    [PATCH 3.12 03/98] ipv4: Don't do expensive useless work during inetdev destroy. Jiri Slaby <jslaby@suse.cz> - 2016-04-11 16:10 +0200
    [PATCH 3.12 27/98] perf, nmi: Fix unknown NMI warning Jiri Slaby <jslaby@suse.cz> - 2016-04-11 16:10 +0200
    [PATCH 3.12 14/98] sched: Fix race between task_group and sched_task_group Jiri Slaby <jslaby@suse.cz> - 2016-04-11 16:10 +0200
    [PATCH 3.12 20/98] memcg: do not hang on OOM when killed by userspace OOM access to memory reserves Jiri Slaby <jslaby@suse.cz> - 2016-04-11 16:10 +0200
    [PATCH 3.12 19/98] ALSA: seq: Fix leak of pool buffer at concurrent writes Jiri Slaby <jslaby@suse.cz> - 2016-04-11 16:10 +0200
    [PATCH 3.12 09/98] xen-blkback: only read request operation from shared ring once Jiri Slaby <jslaby@suse.cz> - 2016-04-11 16:10 +0200
    [PATCH 3.12 05/98] kernel: Provide READ_ONCE and ASSIGN_ONCE Jiri Slaby <jslaby@suse.cz> - 2016-04-11 16:10 +0200
      Re: [PATCH 3.12 05/98] kernel: Provide READ_ONCE and ASSIGN_ONCE Christian Borntraeger <borntraeger@de.ibm.com> - 2016-04-11 16:20 +0200
    [PATCH 3.12 06/98] xen: Add RING_COPY_REQUEST() Jiri Slaby <jslaby@suse.cz> - 2016-04-11 16:10 +0200
    [PATCH 3.12 17/98] drivers/base/memory.c: fix kernel warning during memory hotplug on ppc64 Jiri Slaby <jslaby@suse.cz> - 2016-04-11 16:10 +0200
    [PATCH 3.12 04/98] umount: Do not allow unmounting rootfs. Jiri Slaby <jslaby@suse.cz> - 2016-04-11 16:10 +0200
    [PATCH 3.12 10/98] xen-blkback: read from indirect descriptors only once Jiri Slaby <jslaby@suse.cz> - 2016-04-11 16:10 +0200
    [PATCH 3.12 02/98] ipr: Fix regression when loading firmware Jiri Slaby <jslaby@suse.cz> - 2016-04-11 16:10 +0200
    [PATCH 3.12 15/98] Btrfs: skip locking when searching commit root Jiri Slaby <jslaby@suse.cz> - 2016-04-11 16:10 +0200
  Re: [PATCH 3.12 00/98] 3.12.58-stable review shuahkh <shuahkh@osg.sisa.samsung.com> - 2016-04-11 19:30 +0200

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