summaryrefslogtreecommitdiffstats
path: root/arch/arc/mm/tlbex.S
blob: 3fcfdb38d242d47512a5aa9a174434d25d6e6450 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
/*
 * TLB Exception Handling for ARC
 *
 * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * Vineetg: April 2011 :
 *  -MMU v1: moved out legacy code into a seperate file
 *  -MMU v3: PD{0,1} bits layout changed: They don't overlap anymore,
 *      helps avoid a shift when preparing PD0 from PTE
 *
 * Vineetg: July 2009
 *  -For MMU V2, we need not do heuristics at the time of commiting a D-TLB
 *   entry, so that it doesn't knock out it's I-TLB entry
 *  -Some more fine tuning:
 *   bmsk instead of add, asl.cc instead of branch, delay slot utilise etc
 *
 * Vineetg: July 2009
 *  -Practically rewrote the I/D TLB Miss handlers
 *   Now 40 and 135 instructions a peice as compared to 131 and 449 resp.
 *   Hence Leaner by 1.5 K
 *   Used Conditional arithmetic to replace excessive branching
 *   Also used short instructions wherever possible
 *
 * Vineetg: Aug 13th 2008
 *  -Passing ECR (Exception Cause REG) to do_page_fault( ) for printing
 *   more information in case of a Fatality
 *
 * Vineetg: March 25th Bug #92690
 *  -Added Debug Code to check if sw-ASID == hw-ASID

 * Rahul Trivedi, Amit Bhor: Codito Technologies 2004
 */

	.cpu A7

#include <linux/linkage.h>
#include <asm/entry.h>
#include <asm/mmu.h>
#include <asm/pgtable.h>
#include <asm/arcregs.h>
#include <asm/cache.h>
#include <asm/processor.h>
#include <asm/tlb-mmu1.h>

;-----------------------------------------------------------------
; ARC700 Exception Handling doesn't auto-switch stack and it only provides
; ONE scratch AUX reg "ARC_REG_SCRATCH_DATA0"
;
; For Non-SMP, the scratch AUX reg is repurposed to cache task PGD, so a
; "global" is used to free-up FIRST core reg to be able to code the rest of
; exception prologue (IRQ auto-disabled on Exceptions, so it's IRQ-safe).
; Since the Fast Path TLB Miss handler is coded with 4 regs, the remaining 3
; need to be saved as well by extending the "global" to be 4 words. Hence
;	".size   ex_saved_reg1, 16"
; [All of this dance is to avoid stack switching for each TLB Miss, since we
; only need to save only a handful of regs, as opposed to complete reg file]
;
; For ARC700 SMP, the "global" obviously can't be used for free up the FIRST
; core reg as it will not be SMP safe.
; Thus scratch AUX reg is used (and no longer used to cache task PGD).
; To save the rest of 3 regs - per cpu, the global is made "per-cpu".
; Epilogue thus has to locate the "per-cpu" storage for regs.
; To avoid cache line bouncing the per-cpu global is aligned/sized per
; L1_CACHE_SHIFT, despite fundamentally needing to be 12 bytes only. Hence
;	".size   ex_saved_reg1, (CONFIG_NR_CPUS << L1_CACHE_SHIFT)"

; As simple as that....
;--------------------------------------------------------------------------

; scratch memory to save [r0-r3] used to code TLB refill Handler
ARCFP_DATA ex_saved_reg1
	.align 1 << L1_CACHE_SHIFT
	.type   ex_saved_reg1, @object
#ifdef CONFIG_SMP
	.size   ex_saved_reg1, (CONFIG_NR_CPUS << L1_CACHE_SHIFT)
ex_saved_reg1:
	.zero (CONFIG_NR_CPUS << L1_CACHE_SHIFT)
#else
	.size   ex_saved_reg1, 16
ex_saved_reg1:
	.zero 16
#endif

.macro TLBMISS_FREEUP_REGS
#ifdef CONFIG_SMP
	sr  r0, [ARC_REG_SCRATCH_DATA0]	; freeup r0 to code with
	GET_CPU_ID  r0			; get to per cpu scratch mem,
	lsl r0, r0, L1_CACHE_SHIFT	; cache line wide per cpu
	add r0, @ex_saved_reg1, r0
#else
	st    r0, [@ex_saved_reg1]
	mov_s r0, @ex_saved_reg1
#endif
	st_s  r1, [r0, 4]
	st_s  r2, [r0, 8]
	st_s  r3, [r0, 12]

	; VERIFY if the ASID in MMU-PID Reg is same as
	; one in Linux data structures

	tlb_paranoid_check_asm
.endm

.macro TLBMISS_RESTORE_REGS
#ifdef CONFIG_SMP
	GET_CPU_ID  r0			; get to per cpu scratch mem
	lsl r0, r0, L1_CACHE_SHIFT	; each is cache line wide
	add r0, @ex_saved_reg1, r0
	ld_s  r3, [r0,12]
	ld_s  r2, [r0, 8]
	ld_s  r1, [r0, 4]
	lr    r0, [ARC_REG_SCRATCH_DATA0]
#else
	mov_s r0, @ex_saved_reg1
	ld_s  r3, [r0,12]
	ld_s  r2, [r0, 8]
	ld_s  r1, [r0, 4]
	ld_s  r0, [r0]
#endif
.endm

;============================================================================
;  Troubleshooting Stuff
;============================================================================

; Linux keeps ASID (Address Space ID) in task->active_mm->context.asid
; When Creating TLB Entries, instead of doing 3 dependent loads from memory,
; we use the MMU PID Reg to get current ASID.
; In bizzare scenrios SW and HW ASID can get out-of-sync which is trouble.
; So we try to detect this in TLB Mis shandler

.macro tlb_paranoid_check_asm

#ifdef CONFIG_ARC_DBG_TLB_PARANOIA

	GET_CURR_TASK_ON_CPU  r3
	ld r0, [r3, TASK_ACT_MM]
	ld r0, [r0, MM_CTXT+MM_CTXT_ASID]
	breq r0, 0, 55f	; Error if no ASID allocated

	lr r1, [ARC_REG_PID]
	and r1, r1, 0xFF

	and r2, r0, 0xFF	; MMU PID bits only for comparison
	breq r1, r2, 5f

55:
	; Error if H/w and S/w ASID don't match, but NOT if in kernel mode
	lr  r2, [erstatus]
	bbit0 r2, STATUS_U_BIT, 5f

	; We sure are in troubled waters, Flag the error, but to do so
	; need to switch to kernel mode stack to call error routine
	GET_TSK_STACK_BASE   r3, sp

	; Call printk to shoutout aloud
	mov r2, 1
	j print_asid_mismatch

5:	; ASIDs match so proceed normally
	nop

#endif

.endm

;============================================================================
;TLB Miss handling Code
;============================================================================

;-----------------------------------------------------------------------------
; This macro does the page-table lookup for the faulting address.
; OUT: r0 = PTE faulted on, r1 = ptr to PTE, r2 = Faulting V-address
.macro LOAD_FAULT_PTE

	lr  r2, [efa]

#ifndef CONFIG_SMP
	lr  r1, [ARC_REG_SCRATCH_DATA0] ; current pgd
#else
	GET_CURR_TASK_ON_CPU  r1
	ld  r1, [r1, TASK_ACT_MM]
	ld  r1, [r1, MM_PGD]
#endif

	lsr     r0, r2, PGDIR_SHIFT     ; Bits for indexing into PGD
	ld.as   r1, [r1, r0]            ; PGD entry corresp to faulting addr
	and.f   r1, r1, PAGE_MASK       ; Ignoring protection and other flags
	;   contains Ptr to Page Table
	bz.d    do_slow_path_pf         ; if no Page Table, do page fault

	; Get the PTE entry: The idea is
	; (1) x = addr >> PAGE_SHIFT 	-> masks page-off bits from @fault-addr
	; (2) y = x & (PTRS_PER_PTE - 1) -> to get index
	; (3) z = pgtbl[y]
	; To avoid the multiply by in end, we do the -2, <<2 below

	lsr     r0, r2, (PAGE_SHIFT - 2)
	and     r0, r0, ( (PTRS_PER_PTE - 1) << 2)
	ld.aw   r0, [r1, r0]            ; get PTE and PTE ptr for fault addr
#ifdef CONFIG_ARC_DBG_TLB_MISS_COUNT
	and.f 0, r0, _PAGE_PRESENT
	bz   1f
	ld   r3, [num_pte_not_present]
	add  r3, r3, 1
	st   r3, [num_pte_not_present]
1:
#endif

.endm

;-----------------------------------------------------------------
; Convert Linux PTE entry into TLB entry
; A one-word PTE entry is programmed as two-word TLB Entry [PD0:PD1] in mmu
; IN: r0 = PTE, r1 = ptr to PTE

.macro CONV_PTE_TO_TLB
	and    r3, r0, PTE_BITS_RWX	;       r w x
	lsl    r2, r3, 3		; r w x 0 0 0
	and.f  0,  r0, _PAGE_GLOBAL
	or.z   r2, r2, r3		; r w x r w x

	and r3, r0, PTE_BITS_NON_RWX_IN_PD1 ; Extract PFN+cache bits from PTE
	or  r3, r3, r2

	sr  r3, [ARC_REG_TLBPD1]    	; these go in PD1

	and r2, r0, PTE_BITS_IN_PD0 ; Extract other PTE flags: (V)alid, (G)lb

	lr  r3,[ARC_REG_TLBPD0]     ; MMU prepares PD0 with vaddr and asid

	or  r3, r3, r2              ; S | vaddr | {sasid|asid}
	sr  r3,[ARC_REG_TLBPD0]     ; rewrite PD0
.endm

;-----------------------------------------------------------------
; Commit the TLB entry into MMU

.macro COMMIT_ENTRY_TO_MMU

	/* Get free TLB slot: Set = computed from vaddr, way = random */
	sr  TLBGetIndex, [ARC_REG_TLBCOMMAND]

	/* Commit the Write */
#if (CONFIG_ARC_MMU_VER >= 2)   /* introduced in v2 */
	sr TLBWriteNI, [ARC_REG_TLBCOMMAND]
#else
	sr TLBWrite, [ARC_REG_TLBCOMMAND]
#endif
.endm


ARCFP_CODE	;Fast Path Code, candidate for ICCM

;-----------------------------------------------------------------------------
; I-TLB Miss Exception Handler
;-----------------------------------------------------------------------------

ARC_ENTRY EV_TLBMissI

	TLBMISS_FREEUP_REGS

#ifdef CONFIG_ARC_DBG_TLB_MISS_COUNT
	ld  r0, [@numitlb]
	add r0, r0, 1
	st  r0, [@numitlb]
#endif

	;----------------------------------------------------------------
	; Get the PTE corresponding to V-addr accessed, r2 is setup with EFA
	LOAD_FAULT_PTE

	;----------------------------------------------------------------
	; VERIFY_PTE: Check if PTE permissions approp for executing code
	cmp_s   r2, VMALLOC_START
	mov_s   r2, (_PAGE_PRESENT | _PAGE_EXECUTE)
	or.hs   r2, r2, _PAGE_GLOBAL

	and     r3, r0, r2  ; Mask out NON Flag bits from PTE
	xor.f   r3, r3, r2  ; check ( ( pte & flags_test ) == flags_test )
	bnz     do_slow_path_pf

	; Let Linux VM know that the page was accessed
	or      r0, r0, _PAGE_ACCESSED  ; set Accessed Bit
	st_s    r0, [r1]                ; Write back PTE

	CONV_PTE_TO_TLB
	COMMIT_ENTRY_TO_MMU
	TLBMISS_RESTORE_REGS
	rtie

ARC_EXIT EV_TLBMissI

;-----------------------------------------------------------------------------
; D-TLB Miss Exception Handler
;-----------------------------------------------------------------------------

ARC_ENTRY EV_TLBMissD

	TLBMISS_FREEUP_REGS

#ifdef CONFIG_ARC_DBG_TLB_MISS_COUNT
	ld  r0, [@numdtlb]
	add r0, r0, 1
	st  r0, [@numdtlb]
#endif

	;----------------------------------------------------------------
	; Get the PTE corresponding to V-addr accessed
	; If PTE exists, it will setup, r0 = PTE, r1 = Ptr to PTE, r2 = EFA
	LOAD_FAULT_PTE

	;----------------------------------------------------------------
	; VERIFY_PTE: Chk if PTE permissions approp for data access (R/W/R+W)

	cmp_s	r2, VMALLOC_START
	mov_s   r2, _PAGE_PRESENT	; common bit for K/U PTE
	or.hs	r2, r2, _PAGE_GLOBAL	; kernel PTE only

	; Linux PTE [RWX] bits are semantically overloaded:
	; -If PAGE_GLOBAL set, they refer to kernel-only flags (vmalloc)
	; -Otherwise they are user-mode permissions, and those are exactly
	;  same for kernel mode as well (e.g. copy_(to|from)_user)

	lr      r3, [ecr]
	btst_s  r3, ECR_C_BIT_DTLB_LD_MISS	; Read Access
	or.nz   r2, r2, _PAGE_READ      	; chk for Read flag in PTE
	btst_s  r3, ECR_C_BIT_DTLB_ST_MISS	; Write Access
	or.nz   r2, r2, _PAGE_WRITE     	; chk for Write flag in PTE
	; Above laddering takes care of XCHG access (both R and W)

	; By now, r2 setup with all the Flags we need to check in PTE
	and     r3, r0, r2              ; Mask out NON Flag bits from PTE
	brne.d  r3, r2, do_slow_path_pf ; is ((pte & flags_test) == flags_test)

	;----------------------------------------------------------------
	; UPDATE_PTE: Let Linux VM know that page was accessed/dirty
	lr      r3, [ecr]
	or      r0, r0, _PAGE_ACCESSED        ; Accessed bit always
	btst_s  r3,  ECR_C_BIT_DTLB_ST_MISS   ; See if it was a Write Access ?
	or.nz   r0, r0, _PAGE_MODIFIED        ; if Write, set Dirty bit as well
	st_s    r0, [r1]                      ; Write back PTE

	CONV_PTE_TO_TLB

#if (CONFIG_ARC_MMU_VER == 1)
	; MMU with 2 way set assoc J-TLB, needs some help in pathetic case of
	; memcpy where 3 parties contend for 2 ways, ensuing a livelock.
	; But only for old MMU or one with Metal Fix
	TLB_WRITE_HEURISTICS
#endif

	COMMIT_ENTRY_TO_MMU
	TLBMISS_RESTORE_REGS
	rtie

;-------- Common routine to call Linux Page Fault Handler -----------
do_slow_path_pf:

	; Restore the 4-scratch regs saved by fast path miss handler
	TLBMISS_RESTORE_REGS

	; Slow path TLB Miss handled as a regular ARC Exception
	; (stack switching / save the complete reg-file).
	EXCEPTION_PROLOGUE

	; ------- setup args for Linux Page fault Hanlder ---------
	mov_s r1, sp
	lr    r0, [efa]

	; We don't want exceptions to be disabled while the fault is handled.
	; Now that we have saved the context we return from exception hence
	; exceptions get re-enable

	FAKE_RET_FROM_EXCPN  r9

	bl  do_page_fault
	b   ret_from_exception

ARC_EXIT EV_TLBMissD

ARC_ENTRY EV_TLBMissB   ; Bogus entry to measure sz of DTLBMiss hdlr