linux/arch/arc/mm/tlbex.S
Vineet Gupta dd7c7ab01a ARC: [plat-eznps]: Drop support for EZChip NPS platform
NPS customers are no longer doing active development, as evident from
rand config build failures reported in recent times, so drop support
for NPS platform.

Tested-by: kernel test robot <lkp@intel.com>
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
2020-10-05 21:02:29 -07:00

411 lines
12 KiB
ArmAsm

/* SPDX-License-Identifier: GPL-2.0-only */
/*
* TLB Exception Handling for ARC
*
* Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
*
* 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
*/
#include <linux/linkage.h>
#include <linux/pgtable.h>
#include <asm/entry.h>
#include <asm/mmu.h>
#include <asm/arcregs.h>
#include <asm/cache.h>
#include <asm/processor.h>
#include <asm/tlb-mmu1.h>
#ifdef CONFIG_ISA_ARCOMPACT
;-----------------------------------------------------------------
; 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,
asl 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
asl 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
#else /* ARCv2 */
.macro TLBMISS_FREEUP_REGS
#ifdef CONFIG_ARC_HAS_LL64
std r0, [sp, -16]
std r2, [sp, -8]
#else
PUSH r0
PUSH r1
PUSH r2
PUSH r3
#endif
.endm
.macro TLBMISS_RESTORE_REGS
#ifdef CONFIG_ARC_HAS_LL64
ldd r0, [sp, -16]
ldd r2, [sp, -8]
#else
POP r3
POP r2
POP r1
POP r0
#endif
.endm
#endif
;============================================================================
; 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]
#ifdef ARC_USE_SCRATCH_REG
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 r3, [r1, r0] ; PGD entry corresp to faulting addr
tst r3, r3
bz do_slow_path_pf ; if no Page Table, do page fault
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
and.f 0, r3, _PAGE_HW_SZ ; Is this Huge PMD (thp)
add2.nz r1, r1, r0
bnz.d 2f ; YES: PGD == PMD has THP PTE: stop pgd walk
mov.nz r0, r3
#endif
and r1, r3, PAGE_MASK
; 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 * 4)
#ifdef CONFIG_ARC_HAS_PAE40
#define PTE_SIZE_LOG 3 /* 8 == 2 ^ 3 */
#else
#define PTE_SIZE_LOG 2 /* 4 == 2 ^ 2 */
#endif
; multiply in step (3) above avoided by shifting lesser in step (1)
lsr r0, r2, ( PAGE_SHIFT - PTE_SIZE_LOG )
and r0, r0, ( (PTRS_PER_PTE - 1) << PTE_SIZE_LOG )
ld.aw r0, [r1, r0] ; r0: PTE (lower word only for PAE40)
; r1: PTE ptr
2:
.endm
;-----------------------------------------------------------------
; Convert Linux PTE entry into TLB entry
; A one-word PTE entry is programmed as two-word TLB Entry [PD0:PD1] in mmu
; (for PAE40, two-words PTE, while three-word TLB Entry [PD0:PD1:PD1HI])
; IN: r0 = PTE, r1 = ptr to PTE
.macro CONV_PTE_TO_TLB
and r3, r0, PTE_BITS_RWX ; r w x
asl r2, r3, 3 ; Kr Kw Kx 0 0 0 (GLOBAL, kernel only)
and.f 0, r0, _PAGE_GLOBAL
or.z r2, r2, r3 ; Kr Kw Kx Ur Uw Ux (!GLOBAL, user page)
and r3, r0, PTE_BITS_NON_RWX_IN_PD1 ; Extract PFN+cache bits from PTE
or r3, r3, r2
sr r3, [ARC_REG_TLBPD1] ; paddr[31..13] | Kr Kw Kx Ur Uw Ux | C
#ifdef CONFIG_ARC_HAS_PAE40
ld r3, [r1, 4] ; paddr[39..32]
sr r3, [ARC_REG_TLBPD1HI]
#endif
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
#if (CONFIG_ARC_MMU_VER < 4)
/* Get free TLB slot: Set = computed from vaddr, way = random */
sr TLBGetIndex, [ARC_REG_TLBCOMMAND]
/* Commit the Write */
sr TLBWriteNI, [ARC_REG_TLBCOMMAND]
#else
sr TLBInsertEntry, [ARC_REG_TLBCOMMAND]
#endif
88:
.endm
ARCFP_CODE ;Fast Path Code, candidate for ICCM
;-----------------------------------------------------------------------------
; I-TLB Miss Exception Handler
;-----------------------------------------------------------------------------
ENTRY(EV_TLBMissI)
TLBMISS_FREEUP_REGS
;----------------------------------------------------------------
; 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
EV_TLBMissI_fast_ret: ; additional label for VDK OS-kit instrumentation
rtie
END(EV_TLBMissI)
;-----------------------------------------------------------------------------
; D-TLB Miss Exception Handler
;-----------------------------------------------------------------------------
ENTRY(EV_TLBMissD)
TLBMISS_FREEUP_REGS
;----------------------------------------------------------------
; 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
or r0, r0, _PAGE_ACCESSED ; Accessed bit always
or.nz r0, r0, _PAGE_DIRTY ; 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
EV_TLBMissD_fast_ret: ; additional label for VDK OS-kit instrumentation
rtie
;-------- Common routine to call Linux Page Fault Handler -----------
do_slow_path_pf:
#ifdef CONFIG_ISA_ARCV2
; Set Z flag if exception in U mode. Hardware micro-ops do this on any
; taken interrupt/exception, and thus is already the case at the entry
; above, but ensuing code would have already clobbered.
; EXCEPTION_PROLOGUE called in slow path, relies on correct Z flag set
lr r2, [erstatus]
and r2, r2, STATUS_U_MASK
bxor.f 0, r2, STATUS_U_BIT
#endif
; 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).
b call_do_page_fault
END(EV_TLBMissD)