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Commit 059dfa6a authored by Wei Liu's avatar Wei Liu Committed by David S. Miller
Browse files

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: default avatarJan Beulich <jbeulich@suse.com>
Signed-off-by: default avatarWei Liu <wei.liu2@citrix.com>
Reviewed-by: default avatarDavid Vrabel <david.vrabel@citrix.com>
Cc: Ian Campbell <ian.campbell@citrix.com>
Cc: Jason Luan <jianhai.luan@oracle.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 262e827f

drivers/net/xen-netback/common.h

+1 −0
Original line number Diff line number Diff line
@@ -163,6 +163,7 @@ struct xenvif { 
	unsigned long   credit_usec;

	unsigned long   remaining_credit;

	struct timer_list credit_timeout;

	u64 credit_window_start;



	/* Statistics */

	unsigned long rx_gso_checksum_fixup;

drivers/net/xen-netback/interface.c

+1 −2
Original line number Diff line number Diff line
@@ -312,8 +312,7 @@ struct xenvif *xenvif_alloc(struct device *parent, domid_t domid, 
	vif->credit_bytes = vif->remaining_credit = ~0UL;

	vif->credit_usec  = 0UL;

	init_timer(&vif->credit_timeout);

	/* Initialize 'expires' now: it's used to track the credit window. */

	vif->credit_timeout.expires = jiffies;

	vif->credit_window_start = get_jiffies_64();



	dev->netdev_ops	= &xenvif_netdev_ops;

	dev->hw_features = NETIF_F_SG | NETIF_F_IP_CSUM | NETIF_F_TSO;

drivers/net/xen-netback/netback.c

+5 −5
Original line number Diff line number Diff line
@@ -1185,9 +1185,8 @@ static int checksum_setup(struct xenvif *vif, struct sk_buff *skb) 


static bool tx_credit_exceeded(struct xenvif *vif, unsigned size)

{

	unsigned long now = jiffies;

	unsigned long next_credit =

		vif->credit_timeout.expires +

	u64 now = get_jiffies_64();

	u64 next_credit = vif->credit_window_start +

		msecs_to_jiffies(vif->credit_usec / 1000);



	/* Timer could already be pending in rare cases. */
@@ -1195,8 +1194,8 @@ static bool tx_credit_exceeded(struct xenvif *vif, unsigned size) 
		return true;



	/* Passed the point where we can replenish credit? */

	if (time_after_eq(now, next_credit)) {

		vif->credit_timeout.expires = now;

	if (time_after_eq64(now, next_credit)) {

		vif->credit_window_start = now;

		tx_add_credit(vif);

	}
@@ -1208,6 +1207,7 @@ static bool tx_credit_exceeded(struct xenvif *vif, unsigned size) 
			tx_credit_callback;

		mod_timer(&vif->credit_timeout,

			  next_credit);

		vif->credit_window_start = next_credit;



		return true;

	}