/*
 * net busy poll support
 * Copyright(c) 2013 Intel Corporation.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms and conditions of the GNU General Public License,
 * version 2, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 * more details.
 *
 * You should have received a copy of the GNU General Public License along with
 * this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin St - Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Author: Eliezer Tamir
 *
 * Contact Information:
 * e1000-devel Mailing List <e1000-devel@lists.sourceforge.net>
 */

#ifndef _LINUX_NET_BUSY_POLL_H
#define _LINUX_NET_BUSY_POLL_H

#include <linux/netdevice.h>
#include <net/ip.h>

#ifdef CONFIG_NET_RX_BUSY_POLL

struct napi_struct;
extern unsigned int sysctl_net_busy_read __read_mostly;
extern unsigned int sysctl_net_busy_poll __read_mostly;

/* return values from ndo_ll_poll */
#define LL_FLUSH_FAILED		-1
#define LL_FLUSH_BUSY		-2

static inline bool net_busy_loop_on(void)
{
	return sysctl_net_busy_poll;
}

static inline u64 busy_loop_us_clock(void)
{
	return local_clock() >> 10;
}

static inline unsigned long sk_busy_loop_end_time(struct sock *sk)
{
	return busy_loop_us_clock() + ACCESS_ONCE(sk->sk_ll_usec);
}

/* in poll/select we use the global sysctl_net_ll_poll value */
static inline unsigned long busy_loop_end_time(void)
{
	return busy_loop_us_clock() + ACCESS_ONCE(sysctl_net_busy_poll);
}

static inline bool sk_can_busy_loop(const struct sock *sk)
{
	return sk->sk_ll_usec && sk->sk_napi_id && !signal_pending(current);
}


static inline bool busy_loop_timeout(unsigned long end_time)
{
	unsigned long now = busy_loop_us_clock();

	return time_after(now, end_time);
}

bool sk_busy_loop(struct sock *sk, int nonblock);

/* used in the NIC receive handler to mark the skb */
static inline void skb_mark_napi_id(struct sk_buff *skb,
				    struct napi_struct *napi)
{
	skb->napi_id = napi->napi_id;
}


#else /* CONFIG_NET_RX_BUSY_POLL */
static inline unsigned long net_busy_loop_on(void)
{
	return 0;
}

static inline unsigned long busy_loop_end_time(void)
{
	return 0;
}

static inline bool sk_can_busy_loop(struct sock *sk)
{
	return false;
}

static inline void skb_mark_napi_id(struct sk_buff *skb,
				    struct napi_struct *napi)
{
}

static inline bool busy_loop_timeout(unsigned long end_time)
{
	return true;
}

static inline bool sk_busy_loop(struct sock *sk, int nonblock)
{
	return false;
}

#endif /* CONFIG_NET_RX_BUSY_POLL */

/* used in the protocol hanlder to propagate the napi_id to the socket */
static inline void sk_mark_napi_id(struct sock *sk, const struct sk_buff *skb)
{
#ifdef CONFIG_NET_RX_BUSY_POLL
	sk->sk_napi_id = skb->napi_id;
#endif
}

/* variant used for unconnected sockets */
static inline void sk_mark_napi_id_once(struct sock *sk,
					const struct sk_buff *skb)
{
#ifdef CONFIG_NET_RX_BUSY_POLL
	if (!sk->sk_napi_id)
		sk->sk_napi_id = skb->napi_id;
#endif
}

#endif /* _LINUX_NET_BUSY_POLL_H */
/option><option value='35'>35</option><option value='40'>40</option></select></td></tr><tr><td class='label'>space:</td><td class='ctrl'><select name='ignorews' onchange='this.form.submit();'><option value='0' selected='selected'>include</option><option value='1'>ignore</option></select></td></tr><tr><td class='label'>mode:</td><td class='ctrl'><select name='dt' onchange='this.form.submit();'><option value='0' selected='selected'>unified</option><option value='1'>ssdiff</option><option value='2'>stat only</option></select></td></tr><tr><td/><td class='ctrl'><noscript><input type='submit' value='reload'/></noscript></td></tr></table></form></div><table summary='commit info' class='commit-info'>
<tr><th>author</th><td>Michael S. Tsirkin &lt;mst@redhat.com&gt;</td><td class='right'>2017-02-03 05:43:52 +0200</td></tr>
<tr><th>committer</th><td>Michael S. Tsirkin &lt;mst@redhat.com&gt;</td><td class='right'>2017-02-03 23:38:50 +0200</td></tr>
<tr><th>commit</th><td colspan='2' class='oid'><a href='/cgit.cgi/linux/net-next.git/commit/?id=0d5415b489f68b58e1983a53793d25d53098ed4b'>0d5415b489f68b58e1983a53793d25d53098ed4b</a> (<a href='/cgit.cgi/linux/net-next.git/patch/?id=0d5415b489f68b58e1983a53793d25d53098ed4b'>patch</a>)</td></tr>
<tr><th>tree</th><td colspan='2' class='oid'><a href='/cgit.cgi/linux/net-next.git/tree/?id=0d5415b489f68b58e1983a53793d25d53098ed4b'>9509a05b5c480b84214714698cffb85943be8124</a></td></tr>
<tr><th>parent</th><td colspan='2' class='oid'><a href='/cgit.cgi/linux/net-next.git/commit/?id=566cf877a1fcb6d6dc0126b076aad062054c2637'>566cf877a1fcb6d6dc0126b076aad062054c2637</a> (<a href='/cgit.cgi/linux/net-next.git/diff/?id=0d5415b489f68b58e1983a53793d25d53098ed4b&amp;id2=566cf877a1fcb6d6dc0126b076aad062054c2637'>diff</a>)</td></tr></table>
<div class='commit-subject'>Revert "vring: Force use of DMA API for ARM-based systems with legacy devices"</div><div class='commit-msg'>This reverts commit c7070619f3408d9a0dffbed9149e6f00479cf43b.

This has been shown to regress on some ARM systems:

by forcing on DMA API usage for ARM systems, we have inadvertently
kicked open a hornets' nest in terms of cache-coherency. Namely that
unless the virtio device is explicitly described as capable of coherent
DMA by firmware, the DMA APIs on ARM and other DT-based platforms will
assume it is non-coherent. This turns out to cause a big problem for the
likes of QEMU and kvmtool, which generate virtio-mmio devices in their
guest DTs but neglect to add the often-overlooked "dma-coherent"
property; as a result, we end up with the guest making non-cacheable
accesses to the vring, the host doing so cacheably, both talking past
each other and things going horribly wrong.

We are working on a safer work-around.

Fixes: c7070619f340 ("vring: Force use of DMA API for ARM-based systems with legacy devices")
Reported-by: Robin Murphy &lt;robin.murphy@arm.com&gt;
Cc: &lt;stable@vger.kernel.org&gt;
Signed-off-by: Will Deacon &lt;will.deacon@arm.com&gt;
Signed-off-by: Michael S. Tsirkin &lt;mst@redhat.com&gt;
Acked-by: Marc Zyngier &lt;marc.zyngier@arm.com&gt;
</div><div class='diffstat-header'><a href='/cgit.cgi/linux/net-next.git/diff/?id=0d5415b489f68b58e1983a53793d25d53098ed4b'>Diffstat</a></div><table summary='diffstat' class='diffstat'><tr><td class='mode'>-rw-r--r--</td><td class='upd'><a href='/cgit.cgi/linux/net-next.git/diff/drivers/virtio/virtio_ring.c?id=0d5415b489f68b58e1983a53793d25d53098ed4b'>drivers/virtio/virtio_ring.c</a></td><td class='right'>7</td><td class='graph'><table summary='file diffstat' width='7%'><tr><td class='add' style='width: 0.0%;'/><td class='rem' style='width: 100.0%;'/><td class='none' style='width: 0.0%;'/></tr></table></td></tr>
</table><div class='diffstat-summary'>1 files changed, 0 insertions, 7 deletions</div><table summary='diff' class='diff'><tr><td><div class='head'>diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c