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xen-netback: use jiffies_64 value to calculate credit timeout
time_after_eq() only works if the delta is < MAX_ULONG/2. For a 32bit Dom0, if netfront sends packets at a very low rate, the time between subsequent calls to tx_credit_exceeded() may exceed MAX_ULONG/2 and the test for timer_after_eq() will be incorrect. Credit will not be replenished and the guest may become unable to send packets (e.g., if prior to the long gap, all credit was exhausted). Use jiffies_64 variant to mitigate this problem for 32bit Dom0. Suggested-by: Jan Beulich <jbeulich@suse.com> Signed-off-by: Wei Liu <wei.liu2@citrix.com> Reviewed-by: David Vrabel <david.vrabel@citrix.com> Cc: Ian Campbell <ian.campbell@citrix.com> Cc: Jason Luan <jianhai.luan@oracle.com> Signed-off-by: David S. Miller <davem@davemloft.net>
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3 changed files with 7 additions and 7 deletions
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@ -163,6 +163,7 @@ struct xenvif {
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unsigned long credit_usec;
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unsigned long remaining_credit;
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struct timer_list credit_timeout;
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u64 credit_window_start;
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/* Statistics */
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unsigned long rx_gso_checksum_fixup;
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@ -312,8 +312,7 @@ struct xenvif *xenvif_alloc(struct device *parent, domid_t domid,
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vif->credit_bytes = vif->remaining_credit = ~0UL;
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vif->credit_usec = 0UL;
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init_timer(&vif->credit_timeout);
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/* Initialize 'expires' now: it's used to track the credit window. */
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vif->credit_timeout.expires = jiffies;
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vif->credit_window_start = get_jiffies_64();
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dev->netdev_ops = &xenvif_netdev_ops;
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dev->hw_features = NETIF_F_SG | NETIF_F_IP_CSUM | NETIF_F_TSO;
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@ -1185,9 +1185,8 @@ static int checksum_setup(struct xenvif *vif, struct sk_buff *skb)
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static bool tx_credit_exceeded(struct xenvif *vif, unsigned size)
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{
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unsigned long now = jiffies;
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unsigned long next_credit =
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vif->credit_timeout.expires +
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u64 now = get_jiffies_64();
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u64 next_credit = vif->credit_window_start +
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msecs_to_jiffies(vif->credit_usec / 1000);
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/* Timer could already be pending in rare cases. */
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@ -1195,8 +1194,8 @@ static bool tx_credit_exceeded(struct xenvif *vif, unsigned size)
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return true;
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/* Passed the point where we can replenish credit? */
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if (time_after_eq(now, next_credit)) {
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vif->credit_timeout.expires = now;
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if (time_after_eq64(now, next_credit)) {
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vif->credit_window_start = now;
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tx_add_credit(vif);
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}
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@ -1208,6 +1207,7 @@ static bool tx_credit_exceeded(struct xenvif *vif, unsigned size)
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tx_credit_callback;
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mod_timer(&vif->credit_timeout,
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next_credit);
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vif->credit_window_start = next_credit;
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return true;
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}
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