[RFC PATCH v1 20/31] ARC: MMU Exception Handling
From: Vineet Gupta
Date: Wed Nov 07 2012 - 04:57:30 EST
* MMU I-TLB / D-TLB Miss Exceptions
- Fast Path TLB Refill Handler
- slowpath TLB creation via do_page_fault() -> update_mmu_cache()
* Duplicate PD Exception Handler
Signed-off-by: Vineet Gupta <vgupta@xxxxxxxxxxxx>
---
arch/arc/include/asm/arcregs.h | 90 ++++++++++
arch/arc/include/asm/tlb-mmu1.h | 104 ++++++++++++
arch/arc/include/asm/tlb.h | 41 +++++
arch/arc/mm/tlb.c | 252 ++++++++++++++++++++++++++++
arch/arc/mm/tlbex.S | 351 +++++++++++++++++++++++++++++++++++++++
5 files changed, 838 insertions(+), 0 deletions(-)
create mode 100644 arch/arc/include/asm/tlb-mmu1.h
create mode 100644 arch/arc/include/asm/tlb.h
create mode 100644 arch/arc/mm/tlbex.S
diff --git a/arch/arc/include/asm/arcregs.h b/arch/arc/include/asm/arcregs.h
index c12eb9b..aedfbf1 100644
--- a/arch/arc/include/asm/arcregs.h
+++ b/arch/arc/include/asm/arcregs.h
@@ -13,6 +13,7 @@
/* Build Configuration Registers */
#define ARC_REG_VECBASE_BCR 0x68
+#define ARC_REG_MMU_BCR 0x6f
/* status32 Bits Positions */
#define STATUS_H_BIT 0 /* CPU Halted */
@@ -36,6 +37,34 @@
#define STATUS_U_MASK (1<<STATUS_U_BIT)
#define STATUS_L_MASK (1<<STATUS_L_BIT)
+/*
+ * ECR: Exception Cause Reg bits-n-pieces
+ * [23:16] = Exception Vector
+ * [15: 8] = Exception Cause Code
+ * [ 7: 0] = Exception Parameters (for certain types only)
+ */
+#define ECR_VEC_MASK 0xff0000
+#define ECR_CODE_MASK 0x00ff00
+#define ECR_PARAM_MASK 0x0000ff
+
+/* Exception Cause Vector Values */
+#define ECR_V_MACH_CHK 0x20
+#define ECR_V_ITLB_MISS 0x21
+#define ECR_V_DTLB_MISS 0x22
+#define ECR_V_PROTV 0x23
+
+/* Protection Violation Exception Cause Code Values */
+#define ECR_C_PROTV_INST_FETCH 0x00
+#define ECR_C_PROTV_LOAD 0x01
+#define ECR_C_PROTV_STORE 0x02
+#define ECR_C_PROTV_XCHG 0x03
+#define ECR_C_PROTV_MISALIG_DATA 0x04
+
+/* DTLB Miss Exception Cause Code Values */
+#define ECR_C_BIT_DTLB_LD_MISS 8
+#define ECR_C_BIT_DTLB_ST_MISS 9
+
+
/* Auxiliary registers */
#define AUX_IDENTITY 4
#define AUX_INTR_VEC_BASE 0x25
@@ -58,6 +87,44 @@
#define TIMER_CTRL_IE (1 << 0) /* Interupt when Count reachs limit */
#define TIMER_CTRL_NH (1 << 1) /* Count only when CPU NOT halted */
+#if defined(CONFIG_ARC_MMU_V1)
+#define CONFIG_ARC_MMU_VER 1
+#elif defined(CONFIG_ARC_MMU_V2)
+#define CONFIG_ARC_MMU_VER 2
+#elif defined(CONFIG_ARC_MMU_V3)
+#define CONFIG_ARC_MMU_VER 3
+#else
+#error "Error: MMU ver"
+#endif
+
+/* MMU Management regs */
+#define ARC_REG_TLBPD0 0x405
+#define ARC_REG_TLBPD1 0x406
+#define ARC_REG_TLBINDEX 0x407
+#define ARC_REG_TLBCOMMAND 0x408
+#define ARC_REG_PID 0x409
+#define ARC_REG_SCRATCH_DATA0 0x418
+
+/* Bits in MMU PID register */
+#define MMU_ENABLE (1 << 31) /* Enable MMU for process */
+
+/* Error code if probe fails */
+#define TLB_LKUP_ERR 0x80000000
+
+/* TLB Commands */
+#define TLBWrite 0x1
+#define TLBRead 0x2
+#define TLBGetIndex 0x3
+#define TLBProbe 0x4
+
+#if (CONFIG_ARC_MMU_VER >= 2)
+#define TLBWriteNI 0x5 /* write JTLB without inv uTLBs */
+#define TLBIVUTLB 0x6 /* explicitly inv uTLBs */
+#else
+#undef TLBWriteNI /* These cmds don't exist on older MMU */
+#undef TLBIVUTLB
+#endif
+
/* Instruction cache related Auxiliary registers */
#define ARC_REG_IC_BCR 0x77 /* Build Config reg */
#define ARC_REG_IC_IVIC 0x10
@@ -205,6 +272,24 @@ struct arc_fpu {
* Build Configuration Registers, with encoded hardware config
*/
+struct bcr_mmu_1_2 {
+#ifdef CONFIG_CPU_BIG_ENDIAN
+ unsigned int ver:8, ways:4, sets:4, u_itlb:8, u_dtlb:8;
+#else
+ unsigned int u_dtlb:8, u_itlb:8, sets:4, ways:4, ver:8;
+#endif
+};
+
+struct bcr_mmu_3 {
+#ifdef CONFIG_CPU_BIG_ENDIAN
+ unsigned int ver:8, ways:4, sets:4, osm:1, reserv:3, pg_sz:4,
+ u_itlb:4, u_dtlb:4;
+#else
+ unsigned int u_dtlb:4, u_itlb:4, pg_sz:4, reserv:3, osm:1, sets:4,
+ ways:4, ver:8;
+#endif
+};
+
struct bcr_cache {
#ifdef CONFIG_CPU_BIG_ENDIAN
unsigned int pad:12, line_len:4, sz:4, config:4, ver:8;
@@ -218,12 +303,17 @@ struct bcr_cache {
* Generic structures to hold build configuration used at runtime
*/
+struct cpuinfo_arc_mmu {
+ unsigned int ver, pg_sz, sets, ways, u_dtlb, u_itlb, num_tlb;
+};
+
struct cpuinfo_arc_cache {
unsigned int has_aliasing, sz, line_len, assoc, ver;
};
struct cpuinfo_arc {
struct cpuinfo_arc_cache icache, dcache;
+ struct cpuinfo_arc_mmu mmu;
};
extern struct cpuinfo_arc cpuinfo_arc700[];
diff --git a/arch/arc/include/asm/tlb-mmu1.h b/arch/arc/include/asm/tlb-mmu1.h
new file mode 100644
index 0000000..a5ff961
--- /dev/null
+++ b/arch/arc/include/asm/tlb-mmu1.h
@@ -0,0 +1,104 @@
+/*
+ * 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.
+ */
+
+#ifndef __ASM_TLB_MMU_V1_H__
+#define __ASM_TLB_MMU_V1_H__
+
+#if defined(__ASSEMBLY__) && defined(CONFIG_ARC_MMU_VER == 1)
+
+#include <asm/tlb.h>
+
+.macro TLB_WRITE_HEURISTICS
+
+#define JH_HACK1
+#undef JH_HACK2
+#undef JH_HACK3
+
+#ifdef JH_HACK3
+; Calculate set index for 2-way MMU
+; -avoiding use of GetIndex from MMU
+; and its unpleasant LFSR pseudo-random sequence
+;
+; r1 = TLBPD0 from TLB_RELOAD above
+;
+; -- jh_ex_way_set not cleared on startup
+; didn't want to change setup.c
+; hence extra instruction to clean
+;
+; -- should be in cache since in same line
+; as r0/r1 saves above
+;
+ld r0,[jh_ex_way_sel] ; victim pointer
+and r0,r0,1 ; clean
+xor.f r0,r0,1 ; flip
+st r0,[jh_ex_way_sel] ; store back
+asr r0,r1,12 ; get set # <<1, note bit 12=R=0
+or.nz r0,r0,1 ; set way bit
+and r0,r0,0xff ; clean
+sr r0,[ARC_REG_TLBINDEX]
+#endif
+
+#ifdef JH_HACK2
+; JH hack #2
+; Faster than hack #1 in non-thrash case, but hard-coded for 2-way MMU
+; Slower in thrash case (where it matters) because more code is executed
+; Inefficient due to two-register paradigm of this miss handler
+;
+/* r1 = data TLBPD0 at this point */
+lr r0,[eret] /* instruction address */
+xor r0,r0,r1 /* compare set # */
+and.f r0,r0,0x000fe000 /* 2-way MMU mask */
+bne 88f /* not in same set - no need to probe */
+
+lr r0,[eret] /* instruction address */
+and r0,r0,PAGE_MASK /* VPN of instruction address */
+; lr r1,[ARC_REG_TLBPD0] /* Data VPN+ASID - already in r1 from TLB_RELOAD*/
+and r1,r1,0xff /* Data ASID */
+or r0,r0,r1 /* Instruction address + Data ASID */
+
+lr r1,[ARC_REG_TLBPD0] /* save TLBPD0 containing data TLB*/
+sr r0,[ARC_REG_TLBPD0] /* write instruction address to TLBPD0 */
+sr TLBProbe, [ARC_REG_TLBCOMMAND] /* Look for instruction */
+lr r0,[ARC_REG_TLBINDEX] /* r0 = index where instruction is, if at all */
+sr r1,[ARC_REG_TLBPD0] /* restore TLBPD0 */
+
+xor r0,r0,1 /* flip bottom bit of data index */
+b.d 89f
+sr r0,[ARC_REG_TLBINDEX] /* and put it back */
+88:
+sr TLBGetIndex, [ARC_REG_TLBCOMMAND]
+89:
+#endif
+
+#ifdef JH_HACK1
+;
+; Always checks whether instruction will be kicked out by dtlb miss
+;
+mov_s r3, r1 ; save PD0 prepared by TLB_RELOAD in r3
+lr r0,[eret] /* instruction address */
+and r0,r0,PAGE_MASK /* VPN of instruction address */
+bmsk r1,r3,7 /* Data ASID, bits 7-0 */
+or_s r0,r0,r1 /* Instruction address + Data ASID */
+
+sr r0,[ARC_REG_TLBPD0] /* write instruction address to TLBPD0 */
+sr TLBProbe, [ARC_REG_TLBCOMMAND] /* Look for instruction */
+lr r0,[ARC_REG_TLBINDEX] /* r0 = index where instruction is, if at all */
+sr r3,[ARC_REG_TLBPD0] /* restore TLBPD0 */
+
+sr TLBGetIndex, [ARC_REG_TLBCOMMAND]
+lr r1,[ARC_REG_TLBINDEX] /* r1 = index where MMU wants to put data */
+cmp r0,r1 /* if no match on indices, go around */
+xor.eq r1,r1,1 /* flip bottom bit of data index */
+sr r1,[ARC_REG_TLBINDEX] /* and put it back */
+#endif
+
+.endm
+
+#endif
+
+#endif
diff --git a/arch/arc/include/asm/tlb.h b/arch/arc/include/asm/tlb.h
new file mode 100644
index 0000000..b571e12
--- /dev/null
+++ b/arch/arc/include/asm/tlb.h
@@ -0,0 +1,41 @@
+/*
+ * 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.
+ */
+
+#ifndef _ASM_ARC_TLB_H
+#define _ASM_ARC_TLB_H
+
+#ifdef __KERNEL__
+
+#include <asm/pgtable.h>
+
+/* Masks for actual TLB "PD"s */
+#define PTE_BITS_IN_PD0 (_PAGE_GLOBAL | _PAGE_PRESENT)
+#define PTE_BITS_IN_PD1 (PAGE_MASK | _PAGE_CACHEABLE | \
+ _PAGE_EXECUTE | _PAGE_WRITE | _PAGE_READ | \
+ _PAGE_K_EXECUTE | _PAGE_K_WRITE | _PAGE_K_READ)
+
+#ifndef __ASSEMBLY__
+
+#include <linux/pagemap.h>
+#include <asm-generic/tlb.h>
+
+#ifdef CONFIG_ARC_DBG_TLB_PARANOIA
+void tlb_paranoid_check(unsigned int pid_sw, unsigned long address);
+#else
+#define tlb_paranoid_check(a, b)
+#endif
+
+void arc_mmu_init(void);
+extern char *arc_mmu_mumbojumbo(int cpu_id, char *buf, int len);
+void __init read_decode_mmu_bcr(void);
+
+#endif /* __ASSEMBLY__ */
+
+#endif /* __KERNEL__ */
+
+#endif /* _ASM_ARC_TLB_H */
diff --git a/arch/arc/mm/tlb.c b/arch/arc/mm/tlb.c
index f1edae2..41afc84 100644
--- a/arch/arc/mm/tlb.c
+++ b/arch/arc/mm/tlb.c
@@ -21,3 +21,255 @@ int asid_cache = FIRST_ASID;
* see get_new_mmu_context (asm-arc/mmu_context.h)
*/
struct mm_struct *asid_mm_map[NUM_ASID + 1];
+
+
+/*
+ * Routine to create a TLB entry
+ */
+void create_tlb(struct vm_area_struct *vma, unsigned long address, pte_t *ptep)
+{
+ unsigned long flags;
+ unsigned int idx, asid_or_sasid;
+ unsigned long pd0_flags;
+
+ local_irq_save(flags);
+
+ tlb_paranoid_check(vma->vm_mm->context.asid, address);
+
+ address &= PAGE_MASK;
+
+ /* update this PTE credentials */
+ pte_val(*ptep) |= (_PAGE_PRESENT | _PAGE_ACCESSED);
+
+ /* Create HW TLB entry Flags (in PD0) from PTE Flags */
+#if (CONFIG_ARC_MMU_VER <= 2)
+ pd0_flags = ((pte_val(*ptep) & PTE_BITS_IN_PD0) >> 1);
+#else
+ pd0_flags = ((pte_val(*ptep) & PTE_BITS_IN_PD0));
+#endif
+
+ /* ASID for this task */
+ asid_or_sasid = read_aux_reg(ARC_REG_PID) & 0xff;
+
+ write_aux_reg(ARC_REG_TLBPD0, address | pd0_flags | asid_or_sasid);
+
+ /* Load remaining info in PD1 (Page Frame Addr and Kx/Kw/Kr Flags) */
+ write_aux_reg(ARC_REG_TLBPD1, (pte_val(*ptep) & PTE_BITS_IN_PD1));
+
+ /* First verify if entry for this vaddr+ASID already exists */
+ write_aux_reg(ARC_REG_TLBCOMMAND, TLBProbe);
+ idx = read_aux_reg(ARC_REG_TLBINDEX);
+
+ /*
+ * If Not already present get a free slot from MMU.
+ * Otherwise, Probe would have located the entry and set INDEX Reg
+ * with existing location. This will cause Write CMD to over-write
+ * existing entry with new PD0 and PD1
+ */
+ if (likely(idx & TLB_LKUP_ERR))
+ write_aux_reg(ARC_REG_TLBCOMMAND, TLBGetIndex);
+
+ /*
+ * Commit the Entry to MMU
+ * It doesnt sound safe to use the TLBWriteNI cmd here
+ * which doesn't flush uTLBs. I'd rather be safe than sorry.
+ */
+ write_aux_reg(ARC_REG_TLBCOMMAND, TLBWrite);
+
+ local_irq_restore(flags);
+}
+
+/* arch hook called by core VM at the end of handle_mm_fault( ),
+ * when a new PTE is entered in Page Tables or an existing one
+ * is modified. We aggresively pre-install a TLB entry
+ */
+
+void update_mmu_cache(struct vm_area_struct *vma, unsigned long vaddress,
+ pte_t *ptep)
+{
+ /* XXX: This definitely seems useless */
+#if 0
+ BUG_ON(!pfn_valid(pte_pfn(*ptep)));
+#endif
+
+ /* XXX: This is useful - but only once during execve - check why?
+ * handle_mm_fault()
+ * __get_user_pages
+ * copy_strings()
+ * do_execve()
+ */
+ if (current->active_mm != vma->vm_mm)
+ return;
+
+ create_tlb(vma, vaddress, ptep);
+}
+
+/* Read the Cache Build Confuration Registers, Decode them and save into
+ * the cpuinfo structure for later use.
+ * No Validation is done here, simply read/convert the BCRs
+ */
+void __init read_decode_mmu_bcr(void)
+{
+ unsigned int tmp;
+ struct bcr_mmu_1_2 *mmu2; /* encoded MMU2 attr */
+ struct bcr_mmu_3 *mmu3; /* encoded MMU3 attr */
+ struct cpuinfo_arc_mmu *mmu = &cpuinfo_arc700[smp_processor_id()].mmu;
+
+ tmp = read_aux_reg(ARC_REG_MMU_BCR);
+ mmu->ver = (tmp >> 24);
+
+ if (mmu->ver <= 2) {
+ mmu2 = (struct bcr_mmu_1_2 *)&tmp;
+ mmu->pg_sz = PAGE_SIZE;
+ mmu->sets = 1 << mmu2->sets;
+ mmu->ways = 1 << mmu2->ways;
+ mmu->u_dtlb = mmu2->u_dtlb;
+ mmu->u_itlb = mmu2->u_itlb;
+ } else {
+ mmu3 = (struct bcr_mmu_3 *)&tmp;
+ mmu->pg_sz = 512 << mmu3->pg_sz;
+ mmu->sets = 1 << mmu3->sets;
+ mmu->ways = 1 << mmu3->ways;
+ mmu->u_dtlb = mmu3->u_dtlb;
+ mmu->u_itlb = mmu3->u_itlb;
+ }
+
+ mmu->num_tlb = mmu->sets * mmu->ways;
+}
+
+void __init arc_mmu_init(void)
+{
+ /*
+ * ASID mgmt data structures are compile time init
+ * asid_cache = FIRST_ASID and asid_mm_map[] all zeroes
+ */
+
+ local_flush_tlb_all();
+
+ /* Enable the MMU */
+ write_aux_reg(ARC_REG_PID, MMU_ENABLE);
+}
+
+/*
+ * TLB Programmer's Model uses Linear Indexes: 0 to {255, 511} for 128 x {2,4}
+ * The mapping is Column-first.
+ * --------------------- -----------
+ * |way0|way1|way2|way3| |way0|way1|
+ * --------------------- -----------
+ * [set0] | 0 | 1 | 2 | 3 | | 0 | 1 |
+ * [set1] | 4 | 5 | 6 | 7 | | 2 | 3 |
+ * ~ ~ ~ ~
+ * [set127] | 508| 509| 510| 511| | 254| 255|
+ * --------------------- -----------
+ * For normal operations we don't(must not) care how above works since
+ * MMU cmd getIndex(vaddr) abstracts that out.
+ * However for walking WAYS of a SET, we need to know this
+ */
+#define SET_WAY_TO_IDX(mmu, set, way) ((set) * mmu->ways + (way))
+
+/* Handling of Duplicate PD (TLB entry) in MMU.
+ * -Could be due to buggy customer tapeouts or obscure kernel bugs
+ * -MMU complaints not at the time of duplicate PD installation, but at the
+ * time of lookup matching multiple ways.
+ * -Ideally these should never happen - but if they do - workaround by deleting
+ * the duplicate one.
+ * -Knob to be verbose abt it.(TODO: hook them up to debugfs)
+ */
+volatile int dup_pd_verbose = 1;/* Be slient abt it or complain (default) */
+
+void do_tlb_overlap_fault(unsigned long cause, unsigned long address,
+ struct pt_regs *regs)
+{
+ int set, way, n;
+ unsigned int pd0[4], pd1[4]; /* assume max 4 ways */
+ unsigned long flags, is_valid;
+ struct cpuinfo_arc_mmu *mmu = &cpuinfo_arc700[smp_processor_id()].mmu;
+
+ local_irq_save(flags);
+
+ /* re-enable the MMU */
+ write_aux_reg(ARC_REG_PID, MMU_ENABLE | read_aux_reg(ARC_REG_PID));
+
+ /* loop thru all sets of TLB */
+ for (set = 0; set < mmu->sets; set++) {
+
+ /* read out all the ways of current set */
+ for (way = 0, is_valid = 0; way < mmu->ways; way++) {
+ write_aux_reg(ARC_REG_TLBINDEX,
+ SET_WAY_TO_IDX(mmu, set, way));
+ write_aux_reg(ARC_REG_TLBCOMMAND, TLBRead);
+ pd0[way] = read_aux_reg(ARC_REG_TLBPD0);
+ pd1[way] = read_aux_reg(ARC_REG_TLBPD1);
+ is_valid |= pd0[way] & _PAGE_PRESENT;
+ }
+
+ /* If all the WAYS in SET are empty, skip to next SET */
+ if (!is_valid)
+ continue;
+
+ /* Scan the set for duplicate ways: needs a nested loop */
+ for (way = 0; way < mmu->ways; way++) {
+ if (!pd0[way])
+ continue;
+
+ for (n = way + 1; n < mmu->ways; n++) {
+ if ((pd0[way] & PAGE_MASK) ==
+ (pd0[n] & PAGE_MASK)) {
+
+ if (dup_pd_verbose) {
+ pr_info("Duplicate PD's @"
+ "[%d:%d]/[%d:%d]\n",
+ set, way, set, n);
+ pr_info("TLBPD0[%u]: %08x\n",
+ way, pd0[way]);
+ }
+
+ /*
+ * clear entry @way and not @n. This is
+ * critical to our optimised loop
+ */
+ pd0[way] = pd1[way] = 0;
+ write_aux_reg(ARC_REG_TLBINDEX,
+ SET_WAY_TO_IDX(mmu, set, way));
+ __tlb_entry_erase();
+ }
+ }
+ }
+ }
+
+ local_irq_restore(flags);
+}
+
+/***********************************************************************
+ * Diagnostic Routines
+ * -Called from Low Level TLB Hanlders if things don;t look good
+ **********************************************************************/
+
+#ifdef CONFIG_ARC_DBG_TLB_PARANOIA
+
+/*
+ * Low Level ASM TLB handler calls this if it finds that HW and SW ASIDS
+ * don't match
+ */
+void print_asid_mismatch(int is_fast_path)
+{
+ int pid_sw, pid_hw;
+ pid_sw = current->active_mm->context.asid;
+ pid_hw = read_aux_reg(ARC_REG_PID) & 0xff;
+
+ pr_emerg("ASID Mismatch in %s Path Handler: sw-pid=0x%x hw-pid=0x%x\n",
+ is_fast_path ? "Fast" : "Slow", pid_sw, pid_hw);
+
+ __asm__ __volatile__("flag 1");
+}
+
+void tlb_paranoid_check(unsigned int pid_sw, unsigned long addr)
+{
+ unsigned int pid_hw;
+
+ pid_hw = read_aux_reg(ARC_REG_PID) & 0xff;
+
+ if (addr < 0x70000000 && ((pid_hw != pid_sw) || (pid_sw == NO_ASID)))
+ print_asid_mismatch(0);
+}
+#endif
diff --git a/arch/arc/mm/tlbex.S b/arch/arc/mm/tlbex.S
new file mode 100644
index 0000000..fc5b971
--- /dev/null
+++ b/arch/arc/mm/tlbex.S
@@ -0,0 +1,351 @@
+/*
+ * 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/tlb.h>
+#include <asm/pgtable.h>
+#include <asm/arcregs.h>
+#include <asm/cache.h>
+#include <asm/processor.h>
+#if (CONFIG_ARC_MMU_VER == 1)
+#include <asm/tlb-mmu1.h>
+#endif
+
+;--------------------------------------------------------------------------
+; scratch memory to save the registers (r0-r3) used to code TLB refill Handler
+; For details refer to comments before TLBMISS_FREEUP_REGS below
+;--------------------------------------------------------------------------
+
+ .section .data
+ .global ex_saved_reg1
+ .align 1 << L1_CACHE_SHIFT ; IMP: Must be Cache Line aligned
+ .type ex_saved_reg1, @object
+ .size ex_saved_reg1, 16
+ex_saved_reg1:
+ .zero 16
+
+;============================================================================
+; 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 DBG_ASID_MISMATCH
+
+#ifdef CONFIG_ARC_DBG_TLB_PARANOIA
+
+ ; make sure h/w ASID is same as s/w ASID
+
+ GET_CURR_TASK_ON_CPU r3
+ ld r0, [r3, TASK_ACT_MM]
+ ld r0, [r0, MM_CTXT+MM_CTXT_ASID]
+
+ lr r1, [ARC_REG_PID]
+ and r1, r1, 0xFF
+ breq r1, r0, 5f
+
+ ; Error if H/w and S/w ASID don't match, but NOT if in kernel mode
+ lr r0, [erstatus]
+ bbit0 r0, 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 r0, 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]
+
+ lr r1, [ARC_REG_SCRATCH_DATA0] ; current pgd
+
+ 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
+
+.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_IN_PD1 ; Extract permission flags+PFN from PTE
+ sr r3, [ARC_REG_TLBPD1] ; these go in PD1
+
+ and r2, r0, PTE_BITS_IN_PD0 ; Extract other PTE flags: (V)alid, (G)lb
+#if (CONFIG_ARC_MMU_VER <= 2) /* Neednot be done with v3 onwards */
+ lsr r2, r2 ; shift PTE flags to match layout in PD0
+#endif
+
+ 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
+
+;-----------------------------------------------------------------
+; 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]
+
+; As simple as that....
+
+.macro TLBMISS_FREEUP_REGS
+ st r0, [@ex_saved_reg1]
+ mov_s r0, @ex_saved_reg1
+ 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
+
+ DBG_ASID_MISMATCH
+.endm
+
+;-----------------------------------------------------------------
+.macro TLBMISS_RESTORE_REGS
+ 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]
+.endm
+
+.section .text, "ax",@progbits ;Fast Path Code, candidate for ICCM
+
+;-----------------------------------------------------------------------------
+; I-TLB Miss Exception Handler
+;-----------------------------------------------------------------------------
+
+ARC_ENTRY EV_TLBMissI
+
+ TLBMISS_FREEUP_REGS
+
+ ;----------------------------------------------------------------
+ ; Get the PTE corresponding to V-addr accessed
+ LOAD_FAULT_PTE
+
+ ;----------------------------------------------------------------
+ ; VERIFY_PTE: Check if PTE permissions approp for executing code
+ cmp_s r2, VMALLOC_START
+ mov.lo r2, (_PAGE_PRESENT | _PAGE_READ | _PAGE_EXECUTE)
+ mov.hs r2, (_PAGE_PRESENT | _PAGE_K_READ | _PAGE_K_EXECUTE)
+
+ 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_PRESENT | _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
+
+ ;----------------------------------------------------------------
+ ; Get the PTE corresponding to V-addr accessed
+ ; If PTE exists, it will setup, r0 = PTE, r1 = Ptr to PTE
+ LOAD_FAULT_PTE
+
+ ;----------------------------------------------------------------
+ ; VERIFY_PTE: Chk if PTE permissions approp for data access (R/W/R+W)
+
+ mov_s r2, 0
+ 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
+ ; which is both Read and Write
+
+ ; If kernel mode access, ; make _PAGE_xx flags as _PAGE_K_xx
+ ; For copy_(to|from)_user, despite exception taken in kernel mode,
+ ; this code is not hit, because EFA would still be the user mode
+ ; address (EFA < 0x6000_0000).
+ ; This code is for legit kernel mode faults, vmalloc specifically
+ ; (EFA: 0x7000_0000 to 0x7FFF_FFFF)
+
+ lr r3, [efa]
+ cmp r3, VMALLOC_START - 1 ; If kernel mode access
+ asl.hi r2, r2, 3 ; make _PAGE_xx flags as _PAGE_K_xx
+ or r2, r2, _PAGE_PRESENT ; Common flag for K/U mode
+
+ ; 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_PRESENT | _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).
+ ; That requires freeing up r9
+ EXCPN_PROLOG_FREEUP_REG r9
+
+ lr r9, [erstatus]
+
+ SWITCH_TO_KERNEL_STK
+ SAVE_ALL_SYS
+
+ ; ------- setup args for Linux Page fault Hanlder ---------
+ mov_s r0, sp
+ lr r2, [efa]
+ lr r3, [ecr]
+
+ ; Both st and ex imply WRITE access of some sort, hence do_page_fault( )
+ ; invoked with write=1 for DTLB-st/ex Miss and write=0 for ITLB miss or
+ ; DTLB-ld Miss
+ ; DTLB Miss Cause code is ld = 0x01 , st = 0x02, ex = 0x03
+ ; Following code uses that fact that st/ex have one bit in common
+
+ btst_s r3, ECR_C_BIT_DTLB_ST_MISS
+ mov.z r1, 0
+ mov.nz r1, 1
+
+ ; 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
--
1.7.4.1
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