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linux/arch/arc/mm/tlb.c

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/*
* 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 <linux/module.h>
#include <asm/arcregs.h>
#include <asm/setup.h>
#include <asm/mmu_context.h>
#include <asm/tlb.h>
/* 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);
}
/*
* Called at the end of pagefault, for a userspace mapped page
* -pre-install the corresponding TLB entry into MMU
* -Finalize the delayed D-cache flush of kernel mapping of page due to
* flush_dcache_page(), copy_user_page()
*
* Note that flush (when done) involves both WBACK - so physical page is
* in sync as well as INV - so any non-congruent aliases don't remain
*/
void update_mmu_cache(struct vm_area_struct *vma, unsigned long vaddr_unaligned,
pte_t *ptep)
{
unsigned long vaddr = vaddr_unaligned & PAGE_MASK;
unsigned long paddr = pte_val(*ptep) & PAGE_MASK;
create_tlb(vma, vaddr, ptep);
/*
* Exec page : Independent of aliasing/page-color considerations,
* since icache doesn't snoop dcache on ARC, any dirty
* K-mapping of a code page needs to be wback+inv so that
* icache fetch by userspace sees code correctly.
* !EXEC page: If K-mapping is NOT congruent to U-mapping, flush it
* so userspace sees the right data.
* (Avoids the flush for Non-exec + congruent mapping case)
*/
if (vma->vm_flags & VM_EXEC || addr_not_cache_congruent(paddr, vaddr)) {
struct page *page = pfn_to_page(pte_pfn(*ptep));
int dirty = test_and_clear_bit(PG_arch_1, &page->flags);
if (dirty) {
/* wback + inv dcache lines */
__flush_dcache_page(paddr, paddr);
/* invalidate any existing icache lines */
if (vma->vm_flags & VM_EXEC)
__inv_icache_page(paddr, vaddr);
}
}
}
/* 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[cpu_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
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