/* * TLB Management (flush/create/diagnostics) for ARC700 * * 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: Aug 2011 * -Reintroduce duplicate PD fixup - some customer chips still have the issue * * vineetg: May 2011 * -No need to flush_cache_page( ) for each call to update_mmu_cache() * some of the LMBench tests improved amazingly * = page-fault thrice as fast (75 usec to 28 usec) * = mmap twice as fast (9.6 msec to 4.6 msec), * = fork (5.3 msec to 3.7 msec) * * vineetg: April 2011 : * -MMU v3: PD{0,1} bits layout changed: They don't overlap anymore, * helps avoid a shift when preparing PD0 from PTE * * vineetg: April 2011 : Preparing for MMU V3 * -MMU v2/v3 BCRs decoded differently * -Remove TLB_SIZE hardcoding as it's variable now: 256 or 512 * -tlb_entry_erase( ) can be void * -local_flush_tlb_range( ): * = need not "ceil" @end * = walks MMU only if range spans < 32 entries, as opposed to 256 * * Vineetg: Sept 10th 2008 * -Changes related to MMU v2 (Rel 4.8) * * Vineetg: Aug 29th 2008 * -In TLB Flush operations (Metal Fix MMU) there is a explict command to * flush Micro-TLBS. If TLB Index Reg is invalid prior to TLBIVUTLB cmd, * it fails. Thus need to load it with ANY valid value before invoking * TLBIVUTLB cmd * * Vineetg: Aug 21th 2008: * -Reduced the duration of IRQ lockouts in TLB Flush routines * -Multiple copies of TLB erase code seperated into a "single" function * -In TLB Flush routines, interrupt disabling moved UP to retrieve ASID * in interrupt-safe region. * * Vineetg: April 23rd Bug #93131 * Problem: tlb_flush_kernel_range() doesnt do anything if the range to * flush is more than the size of TLB itself. * * Rahul Trivedi : Codito Technologies 2004 */ #include #include #include #include #include /* Need for ARC MMU v2 * * ARC700 MMU-v1 had a Joint-TLB for Code and Data and is 2 way set-assoc. * For a memcpy operation with 3 players (src/dst/code) such that all 3 pages * map into same set, there would be contention for the 2 ways causing severe * Thrashing. * * Although J-TLB is 2 way set assoc, ARC700 caches J-TLB into uTLBS which has * much higher associativity. u-D-TLB is 8 ways, u-I-TLB is 4 ways. * Given this, the thrasing problem should never happen because once the 3 * J-TLB entries are created (even though 3rd will knock out one of the prev * two), the u-D-TLB and u-I-TLB will have what is required to accomplish memcpy * * Yet we still see the Thrashing because a J-TLB Write cause flush of u-TLBs. * This is a simple design for keeping them in sync. So what do we do? * The solution which James came up was pretty neat. It utilised the assoc * of uTLBs by not invalidating always but only when absolutely necessary. * * - Existing TLB commands work as before * - New command (TLBWriteNI) for TLB write without clearing uTLBs * - New command (TLBIVUTLB) to invalidate uTLBs. * * The uTLBs need only be invalidated when pages are being removed from the * OS page table. If a 'victim' TLB entry is being overwritten in the main TLB * as a result of a miss, the removed entry is still allowed to exist in the * uTLBs as it is still valid and present in the OS page table. This allows the * full associativity of the uTLBs to hide the limited associativity of the main * TLB. * * During a miss handler, the new "TLBWriteNI" command is used to load * entries without clearing the uTLBs. * * When the OS page table is updated, TLB entries that may be associated with a * removed page are removed (flushed) from the TLB using TLBWrite. In this * circumstance, the uTLBs must also be cleared. This is done by using the * existing TLBWrite command. An explicit IVUTLB is also required for those * corner cases when TLBWrite was not executed at all because the corresp * J-TLB entry got evicted/replaced. */ /* A copy of the ASID from the PID reg is kept in asid_cache */ int asid_cache = FIRST_ASID; /* ASID to mm struct mapping. We have one extra entry corresponding to * NO_ASID to save us a compare when clearing the mm entry for old asid * see get_new_mmu_context (asm-arc/mmu_context.h) */ struct mm_struct *asid_mm_map[NUM_ASID + 1]; /* * Utility Routine to erase a J-TLB entry * The procedure is to look it up in the MMU. If found, ERASE it by * issuing a TlbWrite CMD with PD0 = PD1 = 0 */ static void __tlb_entry_erase(void) { write_aux_reg(ARC_REG_TLBPD1, 0); write_aux_reg(ARC_REG_TLBPD0, 0); write_aux_reg(ARC_REG_TLBCOMMAND, TLBWrite); } static void tlb_entry_erase(unsigned int vaddr_n_asid) { unsigned int idx; /* Locate the TLB entry for this vaddr + ASID */ write_aux_reg(ARC_REG_TLBPD0, vaddr_n_asid); write_aux_reg(ARC_REG_TLBCOMMAND, TLBProbe); idx = read_aux_reg(ARC_REG_TLBINDEX); /* No error means entry found, zero it out */ if (likely(!(idx & TLB_LKUP_ERR))) { __tlb_entry_erase(); } else { /* Some sort of Error */ /* Duplicate entry error */ if (idx & 0x1) { /* TODO we need to handle this case too */ pr_emerg("unhandled Duplicate flush for %x\n", vaddr_n_asid); } /* else entry not found so nothing to do */ } } /**************************************************************************** * ARC700 MMU caches recently used J-TLB entries (RAM) as uTLBs (FLOPs) * * New IVUTLB cmd in MMU v2 explictly invalidates the uTLB * * utlb_invalidate ( ) * -For v2 MMU calls Flush uTLB Cmd * -For v1 MMU does nothing (except for Metal Fix v1 MMU) * This is because in v1 TLBWrite itself invalidate uTLBs ***************************************************************************/ static void utlb_invalidate(void) { #if (CONFIG_ARC_MMU_VER >= 2) #if (CONFIG_ARC_MMU_VER < 3) /* MMU v2 introduced the uTLB Flush command. * There was however an obscure hardware bug, where uTLB flush would * fail when a prior probe for J-TLB (both totally unrelated) would * return lkup err - because the entry didnt exist in MMU. * The Workround was to set Index reg with some valid value, prior to * flush. This was fixed in MMU v3 hence not needed any more */ unsigned int idx; /* make sure INDEX Reg is valid */ idx = read_aux_reg(ARC_REG_TLBINDEX); /* If not write some dummy val */ if (unlikely(idx & TLB_LKUP_ERR)) write_aux_reg(ARC_REG_TLBINDEX, 0xa); #endif write_aux_reg(ARC_REG_TLBCOMMAND, TLBIVUTLB); #endif } /* * Un-conditionally (without lookup) erase the entire MMU contents */ noinline void local_flush_tlb_all(void) { unsigned long flags; unsigned int entry; struct cpuinfo_arc_mmu *mmu = &cpuinfo_arc700[smp_processor_id()].mmu; local_irq_save(flags); /* Load PD0 and PD1 with template for a Blank Entry */ write_aux_reg(ARC_REG_TLBPD1, 0); write_aux_reg(ARC_REG_TLBPD0, 0); for (entry = 0; entry < mmu->num_tlb; entry++) { /* write this entry to the TLB */ write_aux_reg(ARC_REG_TLBINDEX, entry); write_aux_reg(ARC_REG_TLBCOMMAND, TLBWrite); } utlb_invalidate(); local_irq_restore(flags); } /* * Flush the entrie MM for userland. The fastest way is to move to Next ASID */ noinline void local_flush_tlb_mm(struct mm_struct *mm) { /* * Small optimisation courtesy IA64 * flush_mm called during fork,exit,munmap etc, multiple times as well. * Only for fork( ) do we need to move parent to a new MMU ctxt, * all other cases are NOPs, hence this check. */ if (atomic_read(&mm->mm_users) == 0) return; /* * Workaround for Android weirdism: * A binder VMA could end up in a task such that vma->mm != tsk->mm * old code would cause h/w - s/w ASID to get out of sync */ if (current->mm != mm) destroy_context(mm); else get_new_mmu_context(mm); } /* * Flush a Range of TLB entries for userland. * @start is inclusive, while @end is exclusive * Difference between this and Kernel Range Flush is * -Here the fastest way (if range is too large) is to move to next ASID * without doing any explicit Shootdown * -In case of kernel Flush, entry has to be shot down explictly */ void local_flush_tlb_range(struct vm_area_struct *vma, unsigned long start, unsigned long end) { unsigned long flags; unsigned int asid; /* If range @start to @end is more than 32 TLB entries deep, * its better to move to a new ASID rather than searching for * individual entries and then shooting them down * * The calc above is rough, doesn't account for unaligned parts, * since this is heuristics based anyways */ if (unlikely((end - start) >= PAGE_SIZE * 32)) { local_flush_tlb_mm(vma->vm_mm); return; } /* * @start moved to page start: this alone suffices for checking * loop end condition below, w/o need for aligning @end to end * e.g. 2000 to 4001 will anyhow loop twice */ start &= PAGE_MASK; local_irq_save(flags); asid = vma->vm_mm->context.asid; if (asid != NO_ASID) { while (start < end) { tlb_entry_erase(start | (asid & 0xff)); start += PAGE_SIZE; } } utlb_invalidate(); local_irq_restore(flags); } /* Flush the kernel TLB entries - vmalloc/modules (Global from MMU perspective) * @start, @end interpreted as kvaddr * Interestingly, shared TLB entries can also be flushed using just * @start,@end alone (interpreted as user vaddr), although technically SASID * is also needed. However our smart TLbProbe lookup takes care of that. */ void local_flush_tlb_kernel_range(unsigned long start, unsigned long end) { unsigned long flags; /* exactly same as above, except for TLB entry not taking ASID */ if (unlikely((end - start) >= PAGE_SIZE * 32)) { local_flush_tlb_all(); return; } start &= PAGE_MASK; local_irq_save(flags); while (start < end) { tlb_entry_erase(start); start += PAGE_SIZE; } utlb_invalidate(); local_irq_restore(flags); } /* * Delete TLB entry in MMU for a given page (??? address) * NOTE One TLB entry contains translation for single PAGE */ void local_flush_tlb_page(struct vm_area_struct *vma, unsigned long page) { unsigned long flags; /* Note that it is critical that interrupts are DISABLED between * checking the ASID and using it flush the TLB entry */ local_irq_save(flags); if (vma->vm_mm->context.asid != NO_ASID) { tlb_entry_erase((page & PAGE_MASK) | (vma->vm_mm->context.asid & 0xff)); utlb_invalidate(); } local_irq_restore(flags); } /* * 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; /* * create_tlb() assumes that current->mm == vma->mm, since * -it ASID for TLB entry is fetched from MMU ASID reg (valid for curr) * -completes the lazy write to SASID reg (again valid for curr tsk) * * Removing the assumption involves * -Using vma->mm->context{ASID,SASID}, as opposed to MMU reg. * -Fix the TLB paranoid debug code to not trigger false negatives. * -More importantly it makes this handler inconsistent with fast-path * TLB Refill handler which always deals with "current" * * Lets see the use cases when current->mm != vma->mm and we land here * 1. execve->copy_strings()->__get_user_pages->handle_mm_fault * Here VM wants to pre-install a TLB entry for user stack while * current->mm still points to pre-execve mm (hence the condition). * However the stack vaddr is soon relocated (randomization) and * move_page_tables() tries to undo that TLB entry. * Thus not creating TLB entry is not any worse. * * 2. ptrace(POKETEXT) causes a CoW - debugger(current) inserting a * breakpoint in debugged task. Not creating a TLB now is not * performance critical. * * Both the cases above are not good enough for code churn. */ if (current->active_mm != vma->vm_mm) return; 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) { 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 __cpuinit 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; } char *arc_mmu_mumbojumbo(int cpu_id, char *buf, int len) { int n = 0; struct cpuinfo_arc_mmu *p_mmu = &cpuinfo_arc700[smp_processor_id()].mmu; n += scnprintf(buf + n, len - n, "ARC700 MMU [v%x]\t: %dk PAGE, ", p_mmu->ver, TO_KB(p_mmu->pg_sz)); n += scnprintf(buf + n, len - n, "J-TLB %d (%dx%d), uDTLB %d, uITLB %d, %s\n", p_mmu->num_tlb, p_mmu->sets, p_mmu->ways, p_mmu->u_dtlb, p_mmu->u_itlb, __CONFIG_ARC_MMU_SASID_VAL ? "SASID" : ""); return buf; } void __cpuinit arc_mmu_init(void) { char str[256]; struct cpuinfo_arc_mmu *mmu = &cpuinfo_arc700[smp_processor_id()].mmu; printk(arc_mmu_mumbojumbo(0, str, sizeof(str))); /* For efficiency sake, kernel is compile time built for a MMU ver * This must match the hardware it is running on. * Linux built for MMU V2, if run on MMU V1 will break down because V1 * hardware doesn't understand cmds such as WriteNI, or IVUTLB * On the other hand, Linux built for V1 if run on MMU V2 will do * un-needed workarounds to prevent memcpy thrashing. * Similarly MMU V3 has new features which won't work on older MMU */ if (mmu->ver != CONFIG_ARC_MMU_VER) { panic("MMU ver %d doesn't match kernel built for %d...\n", mmu->ver, CONFIG_ARC_MMU_VER); } if (mmu->pg_sz != PAGE_SIZE) panic("MMU pg size != PAGE_SIZE (%luk)\n", TO_KB(PAGE_SIZE)); /* * 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); /* In smp we use this reg for interrupt 1 scratch */ #ifndef CONFIG_SMP /* swapper_pg_dir is the pgd for the kernel, used by vmalloc */ write_aux_reg(ARC_REG_SCRATCH_DATA0, swapper_pg_dir); #endif } /* * 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