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 "mem/qport.hh"
54#include "params/SnoopFilter.hh"
55#include "sim/sim_object.hh"
56#include "sim/system.hh"
57
58/**
59 * This snoop filter keeps track of which connected port has a
60 * particular line of data. It can be queried (through lookup*) on
61 * memory requests from above (reads / writes / ...); and also from
62 * below (snoops). The snoop filter precisely knows about the location
63 * of lines "above" it through a map from cache line address to
64 * sharers/ports. The snoop filter ties into the flows of requests
65 * (when they succeed at the lower interface), regular responses from
66 * below and also responses from sideway's caches (in update*). This
67 * allows the snoop filter to model cache-line residency by snooping
68 * the messages.
69 *
70 * The tracking happens in two fields to be able to distinguish
71 * between in-flight requests (in requested) and already pulled in
72 * lines (in holder). This distinction is used for producing tighter
73 * assertions and tracking request completion. For safety, (requested
74 * | holder) should be notified and the requesting MSHRs will take
75 * care of ordering.
76 *
77 * Overall, some trickery is required because:
78 * (1) snoops are not followed by an ACK, but only evoke a response if
79 * they need to (hit dirty)
80 * (2) side-channel information is funnelled through direct modifications of
81 * pkt, instead of proper messages through the bus
82 * (3) there are no clean evict messages telling the snoop filter that a local,
83 * upper cache dropped a line, making the snoop filter pessimistic for now
84 * (4) ordering: there is no single point of order in the system. Instead,
85 * requesting MSHRs track order between local requests and remote snoops
86 */
87class SnoopFilter : public SimObject {
88 public:
89 typedef std::vector<QueuedSlavePort*> SnoopList;
90
91 SnoopFilter (const SnoopFilterParams *p) : SimObject(p),
92 linesize(p->system->cacheLineSize()), lookupLatency(p->lookup_latency)
93 {
94 }
95
96 /**
97 * Init a new snoop filter and tell it about all the slave ports of the
98 * enclosing bus.
99 *
100 * @param bus_slave_ports Vector of slave ports that the bus is attached to.
101 */
102 void setSlavePorts(const SnoopList& bus_slave_ports) {
103 slavePorts = bus_slave_ports;
104 }
105
106 /**
107 * Lookup a request (from a slave port) in the snoop filter and return a
108 * list of other slave ports that need forwarding of the resulting snoops.
109 * Additionally, update the tracking structures with new request
110 * information.
111 *
112 * @param cpkt Pointer to the request packet. Not changed.
113 * @param slave_port Slave port where the request came from.
114 * @return Pair of a vector of snoop target ports and lookup latency.
115 */
116 std::pair<SnoopList, Cycles> lookupRequest(const Packet* cpkt,
117 const SlavePort& slave_port);
118
119 /**
120 * For a successful request, update all data structures in the snoop filter
121 * reflecting the changes caused by that request
122 *
123 * @param cpkt Pointer to the request packet. Not changed.
124 * @param slave_port Slave port where the request came from.
125 * @param will_retry This request will retry on this bus / snoop filter
126 */
127 void updateRequest(const Packet* cpkt, const SlavePort& slave_port,
128 bool will_retry);
129
130 /**
131 * Handle an incoming snoop from below (the master port). These can upgrade the
132 * tracking logic and may also benefit from additional steering thanks to the
133 * snoop filter.
134 * @param cpkt Pointer to const Packet containing the snoop.
135 * @return Pair with a vector of SlavePorts that need snooping and a lookup
136 * latency.
137 */
138 std::pair<SnoopList, Cycles> lookupSnoop(const Packet* cpkt);
139
140 /**
141 * Let the snoop filter see any snoop responses that turn into request responses
142 * and indicate cache to cache transfers. These will update the corresponding
143 * state in the filter.
144 *
145 * @param cpkt Pointer to const Packet holding the snoop response.
146 * @param rsp_port SlavePort that sends the response.
147 * @param req_port SlavePort that made the original request and is the
148 * destination of the snoop response.
149 */
150 void updateSnoopResponse(const Packet *cpkt, const SlavePort& rsp_port,
151 const SlavePort& req_port);
152
153 /**
154 * Pass snoop responses that travel downward through the snoop filter and let
155 * them update the snoop filter state. No additional routing happens.
156 *
157 * @param cpkt Pointer to const Packet holding the snoop response.
158 * @param rsp_port SlavePort that sends the response.
159 * @param req_port MasterPort through which the response leaves this cluster.
160 */
161 void updateSnoopForward(const Packet *cpkt, const SlavePort& rsp_port,
162 const MasterPort& req_port);
163
164 /**
165 * Update the snoop filter with a response from below (outer / other cache,
166 * or memory) and update the tracking information in the snoop filter.
167 *
168 * @param cpkt Pointer to const Packet holding the snoop response.
169 * @param slave_port SlavePort that made the original request and is the target
170 * of this response.
171 */
172 void updateResponse(const Packet *cpkt, const SlavePort& slave_port);
173
174 /**
175 * Simple factory methods for standard return values for lookupRequest
176 */
177 std::pair<SnoopList, Cycles> snoopAll(Cycles latency) const
178 {
179 return std::make_pair(slavePorts, latency);
180 }
181 std::pair<SnoopList, Cycles> snoopSelected(const SnoopList& slave_ports,
182 Cycles latency) const
183 {
184 return std::make_pair(slave_ports, latency);
185 }
186 std::pair<SnoopList, Cycles> snoopDown(Cycles latency) const
187 {
188 SnoopList empty;
189 return std::make_pair(empty , latency);
190 }
191
192 virtual void regStats();
193
194 protected:
195 typedef uint64_t SnoopMask;
196 /**
197 * Per cache line item tracking a bitmask of SlavePorts who have an
198 * outstanding request to this line (requested) or already share a cache line
199 * with this address (holder).
200 */
201 struct SnoopItem {
202 SnoopMask requested;
203 SnoopMask holder;
204 };
205 /**
| 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 "mem/qport.hh"
54#include "params/SnoopFilter.hh"
55#include "sim/sim_object.hh"
56#include "sim/system.hh"
57
58/**
59 * This snoop filter keeps track of which connected port has a
60 * particular line of data. It can be queried (through lookup*) on
61 * memory requests from above (reads / writes / ...); and also from
62 * below (snoops). The snoop filter precisely knows about the location
63 * of lines "above" it through a map from cache line address to
64 * sharers/ports. The snoop filter ties into the flows of requests
65 * (when they succeed at the lower interface), regular responses from
66 * below and also responses from sideway's caches (in update*). This
67 * allows the snoop filter to model cache-line residency by snooping
68 * the messages.
69 *
70 * The tracking happens in two fields to be able to distinguish
71 * between in-flight requests (in requested) and already pulled in
72 * lines (in holder). This distinction is used for producing tighter
73 * assertions and tracking request completion. For safety, (requested
74 * | holder) should be notified and the requesting MSHRs will take
75 * care of ordering.
76 *
77 * Overall, some trickery is required because:
78 * (1) snoops are not followed by an ACK, but only evoke a response if
79 * they need to (hit dirty)
80 * (2) side-channel information is funnelled through direct modifications of
81 * pkt, instead of proper messages through the bus
82 * (3) there are no clean evict messages telling the snoop filter that a local,
83 * upper cache dropped a line, making the snoop filter pessimistic for now
84 * (4) ordering: there is no single point of order in the system. Instead,
85 * requesting MSHRs track order between local requests and remote snoops
86 */
87class SnoopFilter : public SimObject {
88 public:
89 typedef std::vector<QueuedSlavePort*> SnoopList;
90
91 SnoopFilter (const SnoopFilterParams *p) : SimObject(p),
92 linesize(p->system->cacheLineSize()), lookupLatency(p->lookup_latency)
93 {
94 }
95
96 /**
97 * Init a new snoop filter and tell it about all the slave ports of the
98 * enclosing bus.
99 *
100 * @param bus_slave_ports Vector of slave ports that the bus is attached to.
101 */
102 void setSlavePorts(const SnoopList& bus_slave_ports) {
103 slavePorts = bus_slave_ports;
104 }
105
106 /**
107 * Lookup a request (from a slave port) in the snoop filter and return a
108 * list of other slave ports that need forwarding of the resulting snoops.
109 * Additionally, update the tracking structures with new request
110 * information.
111 *
112 * @param cpkt Pointer to the request packet. Not changed.
113 * @param slave_port Slave port where the request came from.
114 * @return Pair of a vector of snoop target ports and lookup latency.
115 */
116 std::pair<SnoopList, Cycles> lookupRequest(const Packet* cpkt,
117 const SlavePort& slave_port);
118
119 /**
120 * For a successful request, update all data structures in the snoop filter
121 * reflecting the changes caused by that request
122 *
123 * @param cpkt Pointer to the request packet. Not changed.
124 * @param slave_port Slave port where the request came from.
125 * @param will_retry This request will retry on this bus / snoop filter
126 */
127 void updateRequest(const Packet* cpkt, const SlavePort& slave_port,
128 bool will_retry);
129
130 /**
131 * Handle an incoming snoop from below (the master port). These can upgrade the
132 * tracking logic and may also benefit from additional steering thanks to the
133 * snoop filter.
134 * @param cpkt Pointer to const Packet containing the snoop.
135 * @return Pair with a vector of SlavePorts that need snooping and a lookup
136 * latency.
137 */
138 std::pair<SnoopList, Cycles> lookupSnoop(const Packet* cpkt);
139
140 /**
141 * Let the snoop filter see any snoop responses that turn into request responses
142 * and indicate cache to cache transfers. These will update the corresponding
143 * state in the filter.
144 *
145 * @param cpkt Pointer to const Packet holding the snoop response.
146 * @param rsp_port SlavePort that sends the response.
147 * @param req_port SlavePort that made the original request and is the
148 * destination of the snoop response.
149 */
150 void updateSnoopResponse(const Packet *cpkt, const SlavePort& rsp_port,
151 const SlavePort& req_port);
152
153 /**
154 * Pass snoop responses that travel downward through the snoop filter and let
155 * them update the snoop filter state. No additional routing happens.
156 *
157 * @param cpkt Pointer to const Packet holding the snoop response.
158 * @param rsp_port SlavePort that sends the response.
159 * @param req_port MasterPort through which the response leaves this cluster.
160 */
161 void updateSnoopForward(const Packet *cpkt, const SlavePort& rsp_port,
162 const MasterPort& req_port);
163
164 /**
165 * Update the snoop filter with a response from below (outer / other cache,
166 * or memory) and update the tracking information in the snoop filter.
167 *
168 * @param cpkt Pointer to const Packet holding the snoop response.
169 * @param slave_port SlavePort that made the original request and is the target
170 * of this response.
171 */
172 void updateResponse(const Packet *cpkt, const SlavePort& slave_port);
173
174 /**
175 * Simple factory methods for standard return values for lookupRequest
176 */
177 std::pair<SnoopList, Cycles> snoopAll(Cycles latency) const
178 {
179 return std::make_pair(slavePorts, latency);
180 }
181 std::pair<SnoopList, Cycles> snoopSelected(const SnoopList& slave_ports,
182 Cycles latency) const
183 {
184 return std::make_pair(slave_ports, latency);
185 }
186 std::pair<SnoopList, Cycles> snoopDown(Cycles latency) const
187 {
188 SnoopList empty;
189 return std::make_pair(empty , latency);
190 }
191
192 virtual void regStats();
193
194 protected:
195 typedef uint64_t SnoopMask;
196 /**
197 * Per cache line item tracking a bitmask of SlavePorts who have an
198 * outstanding request to this line (requested) or already share a cache line
199 * with this address (holder).
200 */
201 struct SnoopItem {
202 SnoopMask requested;
203 SnoopMask holder;
204 };
205 /**
|