2 # Copyright 2018 ETH Zurich and University of Bologna.
3 # Copyright and related rights are licensed under the Solderpad Hardware
4 # License, Version 0.51 (the "License"); you may not use this file except in
5 # compliance with the License. You may obtain a copy of the License at
6 # http:#solderpad.org/licenses/SHL-0.51. Unless required by applicable law
7 # or agreed to in writing, software, hardware and materials distributed under
8 # this License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
9 # CONDITIONS OF ANY KIND, either express or implied. See the License for the
10 # specific language governing permissions and limitations under the License.
12 # Author: David Schaffenrath, TU Graz
13 # Author: Florian Zaruba, ETH Zurich
15 # Description: Translation Lookaside Buffer, SV39
16 # fully set-associative
19 from nmigen
import Signal
, Module
, Cat
, Const
, Array
20 from nmigen
.cli
import verilog
, rtlil
21 from nmigen
.lib
.coding
import Encoder
23 from ptw
import TLBUpdate
, PTE
, ASID_WIDTH
30 self
.asid
= Signal(ASID_WIDTH
)
31 # SV39 defines three levels of page tables
40 return Cat(*self
.ports())
43 return self
.flatten().eq(x
.flatten())
46 return [self
.asid
, self
.vpn0
, self
.vpn1
, self
.vpn2
,
47 self
.is_2M
, self
.is_1G
, self
.valid
]
51 def __init__(self
, pte_width
):
52 self
.pte_width
= pte_width
53 self
.flush_i
= Signal() # Flush signal
55 self
.update_i
= TLBUpdate()
59 self
.replace_en_i
= Signal() # replace the following entry,
60 # set by replacement strategy
62 self
.lu_asid_i
= Signal(ASID_WIDTH
)
63 self
.lu_content_o
= Signal(self
.pte_width
)
64 self
.lu_is_2M_o
= Signal()
65 self
.lu_is_1G_o
= Signal()
66 self
.lu_hit_o
= Signal()
68 def elaborate(self
, platform
):
72 content
= Signal(self
.pte_width
)
74 m
.d
.comb
+= [self
.lu_hit_o
.eq(0),
75 self
.lu_is_2M_o
.eq(0),
76 self
.lu_is_1G_o
.eq(0)]
78 # temporaries for 1st level match
79 asid_ok
= Signal(reset_less
=True)
80 vpn2_ok
= Signal(reset_less
=True)
81 tags_ok
= Signal(reset_less
=True)
82 vpn2_hit
= Signal(reset_less
=True)
83 m
.d
.comb
+= [tags_ok
.eq(tags
.valid
),
84 asid_ok
.eq(tags
.asid
== self
.lu_asid_i
),
85 vpn2_ok
.eq(tags
.vpn2
== self
.vpn2
),
86 vpn2_hit
.eq(tags_ok
& asid_ok
& vpn2_ok
)]
87 # temporaries for 2nd level match
88 vpn1_ok
= Signal(reset_less
=True)
89 tags_2M
= Signal(reset_less
=True)
90 vpn0_ok
= Signal(reset_less
=True)
91 vpn0_or_2M
= Signal(reset_less
=True)
92 m
.d
.comb
+= [vpn1_ok
.eq(self
.vpn1
== tags
.vpn1
),
93 tags_2M
.eq(tags
.is_2M
),
94 vpn0_ok
.eq(self
.vpn0
== tags
.vpn0
),
95 vpn0_or_2M
.eq(tags_2M | vpn0_ok
)]
96 # first level match, this may be a giga page,
97 # check the ASID flags as well
100 with m
.If (tags
.is_1G
):
101 m
.d
.sync
+= self
.lu_content_o
.eq(content
)
102 m
.d
.comb
+= [ self
.lu_is_1G_o
.eq(1),
105 # not a giga page hit so check further
106 with m
.Elif(vpn1_ok
):
107 # this could be a 2 mega page hit or a 4 kB hit
109 with m
.If(vpn0_or_2M
):
110 m
.d
.sync
+= self
.lu_content_o
.eq(content
)
111 m
.d
.comb
+= [ self
.lu_is_2M_o
.eq(tags
.is_2M
),
119 replace_valid
= Signal(reset_less
=True)
120 m
.d
.comb
+= replace_valid
.eq(self
.update_i
.valid
& self
.replace_en_i
)
121 with m
.If (self
.flush_i
):
122 # invalidate (flush) conditions: all if zero or just this ASID
123 with m
.If (self
.lu_asid_i
== Const(0, ASID_WIDTH
) |
124 (self
.lu_asid_i
== tags
.asid
)):
125 m
.d
.sync
+= tags
.valid
.eq(0)
128 with m
.Elif(replace_valid
):
129 m
.d
.sync
+= [ # update tag array
130 tags
.asid
.eq(self
.update_i
.asid
),
131 tags
.vpn2
.eq(self
.update_i
.vpn
[18:27]),
132 tags
.vpn1
.eq(self
.update_i
.vpn
[9:18]),
133 tags
.vpn0
.eq(self
.update_i
.vpn
[0:9]),
134 tags
.is_1G
.eq(self
.update_i
.is_1G
),
135 tags
.is_2M
.eq(self
.update_i
.is_2M
),
137 # and content as well
138 content
.eq(self
.update_i
.content
.flatten())
143 return [self
.flush_i
,
145 self
.lu_is_2M_o
, self
.lu_is_1G_o
, self
.lu_hit_o
,
146 ] + self
.update_i
.content
.ports() + self
.update_i
.ports()
151 self
.lu_hit
= Signal(TLB_ENTRIES
)
152 self
.replace_en_o
= Signal(TLB_ENTRIES
)
153 self
.lu_access_i
= Signal()
155 def elaborate(self
, platform
):
158 # -----------------------------------------------
159 # PLRU - Pseudo Least Recently Used Replacement
160 # -----------------------------------------------
162 TLBSZ
= 2*(TLB_ENTRIES
-1)
163 plru_tree
= Signal(TLBSZ
)
165 # The PLRU-tree indexing:
174 # Just predefine which nodes will be set/cleared
175 # E.g. for a TLB with 8 entries, the for-loop is semantically
176 # equivalent to the following pseudo-code:
178 # lu_hit[7]: plru_tree[0, 2, 6] = {1, 1, 1};
179 # lu_hit[6]: plru_tree[0, 2, 6] = {1, 1, 0};
180 # lu_hit[5]: plru_tree[0, 2, 5] = {1, 0, 1};
181 # lu_hit[4]: plru_tree[0, 2, 5] = {1, 0, 0};
182 # lu_hit[3]: plru_tree[0, 1, 4] = {0, 1, 1};
183 # lu_hit[2]: plru_tree[0, 1, 4] = {0, 1, 0};
184 # lu_hit[1]: plru_tree[0, 1, 3] = {0, 0, 1};
185 # lu_hit[0]: plru_tree[0, 1, 3] = {0, 0, 0};
186 # default: begin /* No hit */ end
188 LOG_TLB
= int(log2(TLB_ENTRIES
))
189 for i
in range(TLB_ENTRIES
):
190 # we got a hit so update the pointer as it was least recently used
191 hit
= Signal(reset_less
=True)
192 m
.d
.comb
+= hit
.eq(self
.lu_hit
[i
] & self
.lu_access_i
)
194 # Set the nodes to the values we would expect
195 for lvl
in range(LOG_TLB
):
196 idx_base
= (1<<lvl
)-1
197 # lvl0 <=> MSB, lvl1 <=> MSB-1, ...
198 shift
= LOG_TLB
- lvl
;
199 new_idx
= Const(~
((i
>> (shift
-1)) & 1), 1)
200 print ("plru", i
, lvl
, hex(idx_base
),
201 idx_base
+ (i
>> shift
), shift
, new_idx
)
202 m
.d
.sync
+= plru_tree
[idx_base
+ (i
>> shift
)].eq(new_idx
)
204 # Decode tree to write enable signals
205 # Next for-loop basically creates the following logic for e.g.
206 # an 8 entry TLB (note: pseudo-code obviously):
207 # replace_en[7] = &plru_tree[ 6, 2, 0]; #plru_tree[0,2,6]=={1,1,1}
208 # replace_en[6] = &plru_tree[~6, 2, 0]; #plru_tree[0,2,6]=={1,1,0}
209 # replace_en[5] = &plru_tree[ 5,~2, 0]; #plru_tree[0,2,5]=={1,0,1}
210 # replace_en[4] = &plru_tree[~5,~2, 0]; #plru_tree[0,2,5]=={1,0,0}
211 # replace_en[3] = &plru_tree[ 4, 1,~0]; #plru_tree[0,1,4]=={0,1,1}
212 # replace_en[2] = &plru_tree[~4, 1,~0]; #plru_tree[0,1,4]=={0,1,0}
213 # replace_en[1] = &plru_tree[ 3,~1,~0]; #plru_tree[0,1,3]=={0,0,1}
214 # replace_en[0] = &plru_tree[~3,~1,~0]; #plru_tree[0,1,3]=={0,0,0}
215 # For each entry traverse the tree. If every tree-node matches
216 # the corresponding bit of the entry's index, this is
217 # the next entry to replace.
218 for i
in range(TLB_ENTRIES
):
219 en
= Signal(LOG_TLB
, reset_less
=True)
220 for lvl
in range(LOG_TLB
):
221 idx_base
= (1<<lvl
)-1
222 # lvl0 <=> MSB, lvl1 <=> MSB-1, ...
223 shift
= LOG_TLB
- lvl
;
224 new_idx
= (i
>> (shift
-1)) & 1;
225 plru
= Signal(reset_less
=True)
226 m
.d
.comb
+= plru
.eq(plru_tree
[idx_base
+ (i
>>shift
)])
227 # en &= plru_tree_q[idx_base + (i>>shift)] == new_idx;
229 m
.d
.comb
+= en
[lvl
].eq(~plru
) # yes inverted (using bool())
231 m
.d
.comb
+= en
[lvl
].eq(plru
) # yes inverted (using bool())
232 print ("plru", i
, en
)
233 # boolean logic manipluation:
234 # plur0 & plru1 & plur2 == ~(~plru0 | ~plru1 | ~plru2)
235 m
.d
.comb
+= self
.replace_en_o
[i
].eq(~
Cat(*en
).bool())
242 self
.flush_i
= Signal() # Flush signal
244 self
.lu_access_i
= Signal()
245 self
.lu_asid_i
= Signal(ASID_WIDTH
)
246 self
.lu_vaddr_i
= Signal(64)
247 self
.lu_content_o
= PTE()
248 self
.lu_is_2M_o
= Signal()
249 self
.lu_is_1G_o
= Signal()
250 self
.lu_hit_o
= Signal()
252 self
.pte_width
= len(self
.lu_content_o
.flatten())
253 self
.update_i
= TLBUpdate()
255 def elaborate(self
, platform
):
265 m
.d
.comb
+= [ vpn0
.eq(self
.lu_vaddr_i
[12:21]),
266 vpn1
.eq(self
.lu_vaddr_i
[21:30]),
267 vpn2
.eq(self
.lu_vaddr_i
[30:39]),
270 # SV39 defines three levels of page tables
272 for i
in range(TLB_ENTRIES
):
273 tlc
= TLBContent(self
.pte_width
)
274 setattr(m
.submodules
, "tc%d" % i
, tlc
)
277 tlc
.update_i
= self
.update_i
# saves a lot of graphviz links
278 m
.d
.comb
+= [tlc
.vpn0
.eq(vpn0
),
281 tlc
.flush_i
.eq(self
.flush_i
),
282 #tlc.update_i.eq(self.update_i),
283 tlc
.lu_asid_i
.eq(self
.lu_asid_i
)]
290 # use Encoder to select hit index
291 # XXX TODO: assert that there's only one valid entry (one lu_hit)
292 hitsel
= Encoder(TLB_ENTRIES
)
293 m
.submodules
.hitsel
= hitsel
296 for i
in range(TLB_ENTRIES
):
297 hits
.append(tc
[i
].lu_hit_o
)
298 m
.d
.comb
+= hitsel
.i
.eq(Cat(*hits
))
301 active
= Signal(reset_less
=True)
302 m
.d
.comb
+= active
.eq(~hitsel
.n
)
304 # active hit, send selected as output
305 m
.d
.comb
+= [ self
.lu_is_1G_o
.eq(tc
[idx
].lu_is_1G_o
),
306 self
.lu_is_2M_o
.eq(tc
[idx
].lu_is_2M_o
),
308 self
.lu_content_o
.flatten().eq(tc
[idx
].lu_content_o
),
316 m
.submodules
.plru
= p
318 # connect PLRU inputs/outputs
319 # XXX TODO: assert that there's only one valid entry (one replace_en)
321 for i
in range(TLB_ENTRIES
):
322 en
.append(tc
[i
].replace_en_i
)
323 m
.d
.comb
+= [Cat(*en
).eq(p
.replace_en_o
), # output from PLRU into tags
324 p
.lu_hit
.eq(hitsel
.i
),
325 p
.lu_access_i
.eq(self
.lu_access_i
)]
331 assert (TLB_ENTRIES
% 2 == 0) and (TLB_ENTRIES
> 1), \
332 "TLB size must be a multiple of 2 and greater than 1"
333 assert (ASID_WIDTH
>= 1), \
334 "ASID width must be at least 1"
340 function int countSetBits(logic[TLB_ENTRIES-1:0] vector);
341 automatic int count = 0;
342 foreach (vector[idx]) begin
343 count += vector[idx];
348 assert property (@(posedge clk_i)(countSetBits(lu_hit) <= 1))
349 else $error("More then one hit in TLB!"); $stop(); end
350 assert property (@(posedge clk_i)(countSetBits(replace_en) <= 1))
351 else $error("More then one TLB entry selected for next replace!");
355 return [self
.flush_i
, self
.lu_access_i
,
356 self
.lu_asid_i
, self
.lu_vaddr_i
,
357 self
.lu_is_2M_o
, self
.lu_is_1G_o
, self
.lu_hit_o
,
358 ] + self
.lu_content_o
.ports() + self
.update_i
.ports()
360 if __name__
== '__main__':
362 vl
= rtlil
.convert(tlb
, ports
=tlb
.ports())
363 with
open("test_tlb.il", "w") as f
: