1/*
2 * Copyright (c) 2013 ARM Limited
3 * All rights reserved
4 *
5 * The license below extends only to copyright in the software and shall
6 * not be construed as granting a license to any other intellectual
7 * property including but not limited to intellectual property relating
8 * to a hardware implementation of the functionality of the software
9 * licensed hereunder. You may use the software subject to the license
10 * terms below provided that you ensure that this notice is replicated
11 * unmodified and in its entirety in all distributions of the software,
12 * modified or unmodified, in source code or in binary form.
13 *
14 * Redistribution and use in source and binary forms, with or without
15 * modification, are permitted provided that the following conditions are
16 * met: redistributions of source code must retain the above copyright
17 * notice, this list of conditions and the following disclaimer;
18 * redistributions in binary form must reproduce the above copyright
19 * notice, this list of conditions and the following disclaimer in the
20 * documentation and/or other materials provided with the distribution;
21 * neither the name of the copyright holders nor the names of its
22 * contributors may be used to endorse or promote products derived from
23 * this software without specific prior written permission.
24 *
25 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
26 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
27 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
28 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
29 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
30 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
31 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
32 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
33 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
34 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
35 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
36 *
37 * Authors: Stephan Diestelhorst <stephan.diestelhorst@arm.com>
38 */
39
40/**
41 * @file
42 * Definition of a snoop filter.
43 */
44
45#ifndef __MEM_SNOOP_FILTER_HH__
46#define __MEM_SNOOP_FILTER_HH__
47
48#include <utility>
49
50#include "base/hashmap.hh"
51#include "mem/packet.hh"
52#include "mem/port.hh"
53#include "params/SnoopFilter.hh"
54#include "sim/sim_object.hh"
55#include "sim/system.hh"
56
57/**
58 * This snoop filter keeps track of which connected port has a
59 * particular line of data. It can be queried (through lookup*) on
60 * memory requests from above (reads / writes / ...); and also from
61 * below (snoops). The snoop filter precisely knows about the location
62 * of lines "above" it through a map from cache line address to
63 * sharers/ports. The snoop filter ties into the flows of requests
64 * (when they succeed at the lower interface), regular responses from
65 * below and also responses from sideway's caches (in update*). This
66 * allows the snoop filter to model cache-line residency by snooping
67 * the messages.
68 *
69 * The tracking happens in two fields to be able to distinguish
70 * between in-flight requests (in requested) and already pulled in
71 * lines (in holder). This distinction is used for producing tighter
72 * assertions and tracking request completion. For safety, (requested
73 * | holder) should be notified and the requesting MSHRs will take
74 * care of ordering.
75 *
76 * Overall, some trickery is required because:
77 * (1) snoops are not followed by an ACK, but only evoke a response if
78 * they need to (hit dirty)
79 * (2) side-channel information is funnelled through direct modifications of
80 * pkt, instead of proper messages through the bus
81 * (3) there are no clean evict messages telling the snoop filter that a local,
82 * upper cache dropped a line, making the snoop filter pessimistic for now
83 * (4) ordering: there is no single point of order in the system. Instead,
84 * requesting MSHRs track order between local requests and remote snoops
85 */
86class SnoopFilter : public SimObject {
87 public:
88 typedef std::vector<SlavePort*> SnoopList;
89
90 SnoopFilter (const SnoopFilterParams *p) : SimObject(p),
91 linesize(p->system->cacheLineSize()), lookupLatency(p->lookup_latency)
92 {
93 }
94
95 /**
96 * Init a new snoop filter and tell it about all the slave ports of the
97 * enclosing bus.
98 *
99 * @param bus_slave_ports Vector of slave ports that the bus is attached to.
100 */
101 void setSlavePorts(const std::vector<SlavePort*>& bus_slave_ports) {
102 slavePorts = bus_slave_ports;
103 }
104
105 /**
106 * Lookup a request (from a slave port) in the snoop filter and return a
107 * list of other slave ports that need forwarding of the resulting snoops.
108 * Additionally, update the tracking structures with new request
109 * information.
110 *
111 * @param cpkt Pointer to the request packet. Not changed.
112 * @param slave_port Slave port where the request came from.
113 * @return Pair of a vector of snoop target ports and lookup latency.
114 */
115 std::pair<SnoopList, Cycles> lookupRequest(const Packet* cpkt,
116 const SlavePort& slave_port);
117
118 /**
119 * For a successful request, update all data structures in the snoop filter
120 * reflecting the changes caused by that request
121 *
122 * @param cpkt Pointer to the request packet. Not changed.
123 * @param slave_port Slave port where the request came from.
124 * @param will_retry This request will retry on this bus / snoop filter
125 */
126 void updateRequest(const Packet* cpkt, const SlavePort& slave_port,
127 bool will_retry);
128
129 /**
130 * Handle an incoming snoop from below (the master port). These can upgrade the
131 * tracking logic and may also benefit from additional steering thanks to the
132 * snoop filter.
133 * @param cpkt Pointer to const Packet containing the snoop.
134 * @return Pair with a vector of SlavePorts that need snooping and a lookup
135 * latency.
136 */
137 std::pair<SnoopList, Cycles> lookupSnoop(const Packet* cpkt);
138
139 /**
140 * Let the snoop filter see any snoop responses that turn into request responses
141 * and indicate cache to cache transfers. These will update the corresponding
142 * state in the filter.
143 *
144 * @param cpkt Pointer to const Packet holding the snoop response.
145 * @param rsp_port SlavePort that sends the response.
146 * @param req_port SlavePort that made the original request and is the
147 * destination of the snoop response.
148 */
149 void updateSnoopResponse(const Packet *cpkt, const SlavePort& rsp_port,
150 const SlavePort& req_port);
151
152 /**
153 * Pass snoop responses that travel downward through the snoop filter and let
154 * them update the snoop filter state. No additional routing happens.
155 *
156 * @param cpkt Pointer to const Packet holding the snoop response.
157 * @param rsp_port SlavePort that sends the response.
158 * @param req_port MasterPort through which the response leaves this cluster.
159 */
160 void updateSnoopForward(const Packet *cpkt, const SlavePort& rsp_port,
161 const MasterPort& req_port);
162
163 /**
164 * Update the snoop filter with a response from below (outer / other cache,
165 * or memory) and update the tracking information in the snoop filter.
166 *
167 * @param cpkt Pointer to const Packet holding the snoop response.
168 * @param slave_port SlavePort that made the original request and is the target
169 * of this response.
170 */
171 void updateResponse(const Packet *cpkt, const SlavePort& slave_port);
172
173 /**
174 * Simple factory methods for standard return values for lookupRequest
175 */
176 std::pair<SnoopList, Cycles> snoopAll(Cycles latency) const
177 {
178 return std::make_pair(slavePorts, latency);
179 }
180 std::pair<SnoopList, Cycles> snoopSelected(const SnoopList& slave_ports,
181 Cycles latency) const
182 {
183 return std::make_pair(slave_ports, latency);
184 }
185 std::pair<SnoopList, Cycles> snoopDown(Cycles latency) const
186 {
187 SnoopList empty;
188 return std::make_pair(empty , latency);
189 }
190
| 1/*
2 * Copyright (c) 2013 ARM Limited
3 * All rights reserved
4 *
5 * The license below extends only to copyright in the software and shall
6 * not be construed as granting a license to any other intellectual
7 * property including but not limited to intellectual property relating
8 * to a hardware implementation of the functionality of the software
9 * licensed hereunder. You may use the software subject to the license
10 * terms below provided that you ensure that this notice is replicated
11 * unmodified and in its entirety in all distributions of the software,
12 * modified or unmodified, in source code or in binary form.
13 *
14 * Redistribution and use in source and binary forms, with or without
15 * modification, are permitted provided that the following conditions are
16 * met: redistributions of source code must retain the above copyright
17 * notice, this list of conditions and the following disclaimer;
18 * redistributions in binary form must reproduce the above copyright
19 * notice, this list of conditions and the following disclaimer in the
20 * documentation and/or other materials provided with the distribution;
21 * neither the name of the copyright holders nor the names of its
22 * contributors may be used to endorse or promote products derived from
23 * this software without specific prior written permission.
24 *
25 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
26 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
27 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
28 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
29 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
30 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
31 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
32 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
33 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
34 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
35 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
36 *
37 * Authors: Stephan Diestelhorst <stephan.diestelhorst@arm.com>
38 */
39
40/**
41 * @file
42 * Definition of a snoop filter.
43 */
44
45#ifndef __MEM_SNOOP_FILTER_HH__
46#define __MEM_SNOOP_FILTER_HH__
47
48#include <utility>
49
50#include "base/hashmap.hh"
51#include "mem/packet.hh"
52#include "mem/port.hh"
53#include "params/SnoopFilter.hh"
54#include "sim/sim_object.hh"
55#include "sim/system.hh"
56
57/**
58 * This snoop filter keeps track of which connected port has a
59 * particular line of data. It can be queried (through lookup*) on
60 * memory requests from above (reads / writes / ...); and also from
61 * below (snoops). The snoop filter precisely knows about the location
62 * of lines "above" it through a map from cache line address to
63 * sharers/ports. The snoop filter ties into the flows of requests
64 * (when they succeed at the lower interface), regular responses from
65 * below and also responses from sideway's caches (in update*). This
66 * allows the snoop filter to model cache-line residency by snooping
67 * the messages.
68 *
69 * The tracking happens in two fields to be able to distinguish
70 * between in-flight requests (in requested) and already pulled in
71 * lines (in holder). This distinction is used for producing tighter
72 * assertions and tracking request completion. For safety, (requested
73 * | holder) should be notified and the requesting MSHRs will take
74 * care of ordering.
75 *
76 * Overall, some trickery is required because:
77 * (1) snoops are not followed by an ACK, but only evoke a response if
78 * they need to (hit dirty)
79 * (2) side-channel information is funnelled through direct modifications of
80 * pkt, instead of proper messages through the bus
81 * (3) there are no clean evict messages telling the snoop filter that a local,
82 * upper cache dropped a line, making the snoop filter pessimistic for now
83 * (4) ordering: there is no single point of order in the system. Instead,
84 * requesting MSHRs track order between local requests and remote snoops
85 */
86class SnoopFilter : public SimObject {
87 public:
88 typedef std::vector<SlavePort*> SnoopList;
89
90 SnoopFilter (const SnoopFilterParams *p) : SimObject(p),
91 linesize(p->system->cacheLineSize()), lookupLatency(p->lookup_latency)
92 {
93 }
94
95 /**
96 * Init a new snoop filter and tell it about all the slave ports of the
97 * enclosing bus.
98 *
99 * @param bus_slave_ports Vector of slave ports that the bus is attached to.
100 */
101 void setSlavePorts(const std::vector<SlavePort*>& bus_slave_ports) {
102 slavePorts = bus_slave_ports;
103 }
104
105 /**
106 * Lookup a request (from a slave port) in the snoop filter and return a
107 * list of other slave ports that need forwarding of the resulting snoops.
108 * Additionally, update the tracking structures with new request
109 * information.
110 *
111 * @param cpkt Pointer to the request packet. Not changed.
112 * @param slave_port Slave port where the request came from.
113 * @return Pair of a vector of snoop target ports and lookup latency.
114 */
115 std::pair<SnoopList, Cycles> lookupRequest(const Packet* cpkt,
116 const SlavePort& slave_port);
117
118 /**
119 * For a successful request, update all data structures in the snoop filter
120 * reflecting the changes caused by that request
121 *
122 * @param cpkt Pointer to the request packet. Not changed.
123 * @param slave_port Slave port where the request came from.
124 * @param will_retry This request will retry on this bus / snoop filter
125 */
126 void updateRequest(const Packet* cpkt, const SlavePort& slave_port,
127 bool will_retry);
128
129 /**
130 * Handle an incoming snoop from below (the master port). These can upgrade the
131 * tracking logic and may also benefit from additional steering thanks to the
132 * snoop filter.
133 * @param cpkt Pointer to const Packet containing the snoop.
134 * @return Pair with a vector of SlavePorts that need snooping and a lookup
135 * latency.
136 */
137 std::pair<SnoopList, Cycles> lookupSnoop(const Packet* cpkt);
138
139 /**
140 * Let the snoop filter see any snoop responses that turn into request responses
141 * and indicate cache to cache transfers. These will update the corresponding
142 * state in the filter.
143 *
144 * @param cpkt Pointer to const Packet holding the snoop response.
145 * @param rsp_port SlavePort that sends the response.
146 * @param req_port SlavePort that made the original request and is the
147 * destination of the snoop response.
148 */
149 void updateSnoopResponse(const Packet *cpkt, const SlavePort& rsp_port,
150 const SlavePort& req_port);
151
152 /**
153 * Pass snoop responses that travel downward through the snoop filter and let
154 * them update the snoop filter state. No additional routing happens.
155 *
156 * @param cpkt Pointer to const Packet holding the snoop response.
157 * @param rsp_port SlavePort that sends the response.
158 * @param req_port MasterPort through which the response leaves this cluster.
159 */
160 void updateSnoopForward(const Packet *cpkt, const SlavePort& rsp_port,
161 const MasterPort& req_port);
162
163 /**
164 * Update the snoop filter with a response from below (outer / other cache,
165 * or memory) and update the tracking information in the snoop filter.
166 *
167 * @param cpkt Pointer to const Packet holding the snoop response.
168 * @param slave_port SlavePort that made the original request and is the target
169 * of this response.
170 */
171 void updateResponse(const Packet *cpkt, const SlavePort& slave_port);
172
173 /**
174 * Simple factory methods for standard return values for lookupRequest
175 */
176 std::pair<SnoopList, Cycles> snoopAll(Cycles latency) const
177 {
178 return std::make_pair(slavePorts, latency);
179 }
180 std::pair<SnoopList, Cycles> snoopSelected(const SnoopList& slave_ports,
181 Cycles latency) const
182 {
183 return std::make_pair(slave_ports, latency);
184 }
185 std::pair<SnoopList, Cycles> snoopDown(Cycles latency) const
186 {
187 SnoopList empty;
188 return std::make_pair(empty , latency);
189 }
190
|