source: mainline/kernel/arch/ia64/src/mm/tlb.c@ 38e5675b

/*
 * Copyright (c) 2006 Jakub Jermar
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * - Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 * - Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in the
 *   documentation and/or other materials provided with the distribution.
 * - The name of the author may not be used to endorse or promote products
 *   derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

/** @addtogroup ia64mm
 * @{
 */
/** @file
 */

/*
 * TLB management.
 */

#include <mm/tlb.h>
#include <mm/asid.h>
#include <mm/page.h>
#include <mm/as.h>
#include <arch/mm/tlb.h>
#include <arch/mm/page.h>
#include <arch/mm/vhpt.h>
#include <arch/barrier.h>
#include <arch/interrupt.h>
#include <arch/pal/pal.h>
#include <arch/asm.h>
#include <panic.h>
#include <print.h>
#include <arch.h>
#include <interrupt.h>

#define IO_FRAME_BASE 0xFFFFC000000

/** Invalidate all TLB entries. */
void tlb_invalidate_all(void)
{
        ipl_t ipl;
        uintptr_t adr;
        uint32_t count1, count2, stride1, stride2;
        
        unsigned int i, j;
        
        adr = PAL_PTCE_INFO_BASE();
        count1 = PAL_PTCE_INFO_COUNT1();
        count2 = PAL_PTCE_INFO_COUNT2();
        stride1 = PAL_PTCE_INFO_STRIDE1();
        stride2 = PAL_PTCE_INFO_STRIDE2();
        
        ipl = interrupts_disable();
        
        for (i = 0; i < count1; i++) {
                for (j = 0; j < count2; j++) {
                        asm volatile (
                                "ptc.e %[adr] ;;"
                                :: [adr] "r" (adr)
                        );
                        adr += stride2;
                }
                adr += stride1;
        }
        
        interrupts_restore(ipl);
        
        srlz_d();
        srlz_i();
        
#ifdef CONFIG_VHPT
        vhpt_invalidate_all();
#endif
}

/** Invalidate entries belonging to an address space.
 *
 * @param asid Address space identifier.
 *
 */
void tlb_invalidate_asid(asid_t asid)
{
        tlb_invalidate_all();
}


void tlb_invalidate_pages(asid_t asid, uintptr_t page, size_t cnt)
{
        region_register_t rr;
        bool restore_rr = false;
        int b = 0;
        int c = cnt;
        
        uintptr_t va;
        va = page;
        
        rr.word = rr_read(VA2VRN(va));
        if ((restore_rr = (rr.map.rid != ASID2RID(asid, VA2VRN(va))))) {
                /*
                 * The selected region register does not contain required RID.
                 * Save the old content of the register and replace the RID.
                 */
                region_register_t rr0;
                
                rr0 = rr;
                rr0.map.rid = ASID2RID(asid, VA2VRN(va));
                rr_write(VA2VRN(va), rr0.word);
                srlz_d();
                srlz_i();
        }
        
        while (c >>= 1)
                b++;
        b >>= 1;
        uint64_t ps;
        
        switch (b) {
        case 0: /* cnt 1 - 3 */
                ps = PAGE_WIDTH;
                break;
        case 1: /* cnt 4 - 15 */
                ps = PAGE_WIDTH + 2;
                va &= ~((1 << ps) - 1);
                break;
        case 2: /* cnt 16 - 63 */
                ps = PAGE_WIDTH + 4;
                va &= ~((1 << ps) - 1);
                break;
        case 3: /* cnt 64 - 255 */
                ps = PAGE_WIDTH + 6;
                va &= ~((1 << ps) - 1);
                break;
        case 4: /* cnt 256 - 1023 */
                ps = PAGE_WIDTH + 8;
                va &= ~((1 << ps) - 1);
                break;
        case 5: /* cnt 1024 - 4095 */
                ps = PAGE_WIDTH + 10;
                va &= ~((1 << ps) - 1);
                break;
        case 6: /* cnt 4096 - 16383 */
                ps = PAGE_WIDTH + 12;
                va &= ~((1 << ps) - 1);
                break;
        case 7: /* cnt 16384 - 65535 */
        case 8: /* cnt 65536 - (256K - 1) */
                ps = PAGE_WIDTH + 14;
                va &= ~((1 << ps) - 1);
                break;
        default:
                ps = PAGE_WIDTH + 18;
                va &= ~((1 << ps) - 1);
                break;
        }
        
        for (; va < (page + cnt * PAGE_SIZE); va += (1 << ps))
                asm volatile (
                        "ptc.l %[va], %[ps] ;;"
                        :: [va]"r" (va),
                           [ps] "r" (ps << 2)
                );
        
        srlz_d();
        srlz_i();
        
        if (restore_rr) {
                rr_write(VA2VRN(va), rr.word);
                srlz_d();
                srlz_i();
        }
}

/** Insert data into data translation cache.
 *
 * @param va    Virtual page address.
 * @param asid  Address space identifier.
 * @param entry The rest of TLB entry as required by TLB insertion
 *              format.
 *
 */
void dtc_mapping_insert(uintptr_t va, asid_t asid, tlb_entry_t entry)
{
        tc_mapping_insert(va, asid, entry, true);
}

/** Insert data into instruction translation cache.
 *
 * @param va    Virtual page address.
 * @param asid  Address space identifier.
 * @param entry The rest of TLB entry as required by TLB insertion
 *              format.
 */
void itc_mapping_insert(uintptr_t va, asid_t asid, tlb_entry_t entry)
{
        tc_mapping_insert(va, asid, entry, false);
}

/** Insert data into instruction or data translation cache.
 *
 * @param va    Virtual page address.
 * @param asid  Address space identifier.
 * @param entry The rest of TLB entry as required by TLB insertion
 *              format.
 * @param dtc   If true, insert into data translation cache, use
 *              instruction translation cache otherwise.
 *
 */
void tc_mapping_insert(uintptr_t va, asid_t asid, tlb_entry_t entry, bool dtc)
{
        region_register_t rr;
        bool restore_rr = false;
        
        rr.word = rr_read(VA2VRN(va));
        if ((restore_rr = (rr.map.rid != ASID2RID(asid, VA2VRN(va))))) {
                /*
                 * The selected region register does not contain required RID.
                 * Save the old content of the register and replace the RID.
                 */
                region_register_t rr0;
                
                rr0 = rr;
                rr0.map.rid = ASID2RID(asid, VA2VRN(va));
                rr_write(VA2VRN(va), rr0.word);
                srlz_d();
                srlz_i();
        }
        
        asm volatile (
                "mov r8 = psr ;;\n"
                "rsm %[mask] ;;\n"                 /* PSR_IC_MASK */
                "srlz.d ;;\n"
                "srlz.i ;;\n"
                "mov cr.ifa = %[va]\n"             /* va */
                "mov cr.itir = %[word1] ;;\n"      /* entry.word[1] */
                "cmp.eq p6, p7 = %[dtc], r0 ;;\n"  /* decide between itc and dtc */
                "(p6) itc.i %[word0] ;;\n"
                "(p7) itc.d %[word0] ;;\n"
                "mov psr.l = r8 ;;\n"
                "srlz.d ;;\n"
                :: [mask] "i" (PSR_IC_MASK),
                   [va] "r" (va),
                   [word0] "r" (entry.word[0]),
                   [word1] "r" (entry.word[1]),
                   [dtc] "r" (dtc)
                : "p6", "p7", "r8"
        );
        
        if (restore_rr) {
                rr_write(VA2VRN(va), rr.word);
                srlz_d();
                srlz_i();
        }
}

/** Insert data into instruction translation register.
 *
 * @param va    Virtual page address.
 * @param asid  Address space identifier.
 * @param entry The rest of TLB entry as required by TLB insertion
 *              format.
 * @param tr    Translation register.
 *
 */
void itr_mapping_insert(uintptr_t va, asid_t asid, tlb_entry_t entry, size_t tr)
{
        tr_mapping_insert(va, asid, entry, false, tr);
}

/** Insert data into data translation register.
 *
 * @param va    Virtual page address.
 * @param asid  Address space identifier.
 * @param entry The rest of TLB entry as required by TLB insertion
 *              format.
 * @param tr    Translation register.
 *
 */
void dtr_mapping_insert(uintptr_t va, asid_t asid, tlb_entry_t entry, size_t tr)
{
        tr_mapping_insert(va, asid, entry, true, tr);
}

/** Insert data into instruction or data translation register.
 *
 * @param va    Virtual page address.
 * @param asid  Address space identifier.
 * @param entry The rest of TLB entry as required by TLB insertion
 *              format.
 * @param dtr   If true, insert into data translation register, use
 *              instruction translation register otherwise.
 * @param tr    Translation register.
 *
 */
void tr_mapping_insert(uintptr_t va, asid_t asid, tlb_entry_t entry, bool dtr,
    size_t tr)
{
        region_register_t rr;
        bool restore_rr = false;
        
        rr.word = rr_read(VA2VRN(va));
        if ((restore_rr = (rr.map.rid != ASID2RID(asid, VA2VRN(va))))) {
                /*
                 * The selected region register does not contain required RID.
                 * Save the old content of the register and replace the RID.
                 */
                region_register_t rr0;
                
                rr0 = rr;
                rr0.map.rid = ASID2RID(asid, VA2VRN(va));
                rr_write(VA2VRN(va), rr0.word);
                srlz_d();
                srlz_i();
        }
        
        asm volatile (
                "mov r8 = psr ;;\n"
                "rsm %[mask] ;;\n"                       /* PSR_IC_MASK */
                "srlz.d ;;\n"
                "srlz.i ;;\n"
                "mov cr.ifa = %[va]\n"                   /* va */
                "mov cr.itir = %[word1] ;;\n"            /* entry.word[1] */
                "cmp.eq p6, p7 = %[dtr], r0 ;;\n"        /* decide between itr and dtr */
                "(p6) itr.i itr[%[tr]] = %[word0] ;;\n"
                "(p7) itr.d dtr[%[tr]] = %[word0] ;;\n"
                "mov psr.l = r8 ;;\n"
                "srlz.d ;;\n"
                :: [mask] "i" (PSR_IC_MASK),
                   [va] "r" (va),
                   [word1] "r" (entry.word[1]),
                   [word0] "r" (entry.word[0]),
                   [tr] "r" (tr),
                   [dtr] "r" (dtr)
                : "p6", "p7", "r8"
        );
        
        if (restore_rr) {
                rr_write(VA2VRN(va), rr.word);
                srlz_d();
                srlz_i();
        }
}

/** Insert data into DTLB.
 *
 * @param page  Virtual page address including VRN bits.
 * @param frame Physical frame address.
 * @param dtr   If true, insert into data translation register, use data
 *              translation cache otherwise.
 * @param tr    Translation register if dtr is true, ignored otherwise.
 *
 */
void dtlb_kernel_mapping_insert(uintptr_t page, uintptr_t frame, bool dtr,
    size_t tr)
{
        tlb_entry_t entry;
        
        entry.word[0] = 0;
        entry.word[1] = 0;
        
        entry.p = true;           /* present */
        entry.ma = MA_WRITEBACK;
        entry.a = true;           /* already accessed */
        entry.d = true;           /* already dirty */
        entry.pl = PL_KERNEL;
        entry.ar = AR_READ | AR_WRITE;
        entry.ppn = frame >> PPN_SHIFT;
        entry.ps = PAGE_WIDTH;
        
        if (dtr)
                dtr_mapping_insert(page, ASID_KERNEL, entry, tr);
        else
                dtc_mapping_insert(page, ASID_KERNEL, entry);
}

/** Purge kernel entries from DTR.
 *
 * Purge DTR entries used by the kernel.
 *
 * @param page  Virtual page address including VRN bits.
 * @param width Width of the purge in bits.
 *
 */
void dtr_purge(uintptr_t page, size_t width)
{
        asm volatile (
                "ptr.d %[page], %[width]\n"
                :: [page] "r" (page),
                   [width] "r" (width << 2)
        );
}


/** Copy content of PTE into data translation cache.
 *
 * @param t PTE.
 *
 */
void dtc_pte_copy(pte_t *t)
{
        tlb_entry_t entry;
        
        entry.word[0] = 0;
        entry.word[1] = 0;
        
        entry.p = t->p;
        entry.ma = t->c ? MA_WRITEBACK : MA_UNCACHEABLE;
        entry.a = t->a;
        entry.d = t->d;
        entry.pl = t->k ? PL_KERNEL : PL_USER;
        entry.ar = t->w ? AR_WRITE : AR_READ;
        entry.ppn = t->frame >> PPN_SHIFT;
        entry.ps = PAGE_WIDTH;
        
        dtc_mapping_insert(t->page, t->as->asid, entry);
        
#ifdef CONFIG_VHPT
        vhpt_mapping_insert(t->page, t->as->asid, entry);
#endif
}

/** Copy content of PTE into instruction translation cache.
 *
 * @param t PTE.
 *
 */
void itc_pte_copy(pte_t *t)
{
        tlb_entry_t entry;
        
        entry.word[0] = 0;
        entry.word[1] = 0;
        
        ASSERT(t->x);
        
        entry.p = t->p;
        entry.ma = t->c ? MA_WRITEBACK : MA_UNCACHEABLE;
        entry.a = t->a;
        entry.pl = t->k ? PL_KERNEL : PL_USER;
        entry.ar = t->x ? (AR_EXECUTE | AR_READ) : AR_READ;
        entry.ppn = t->frame >> PPN_SHIFT;
        entry.ps = PAGE_WIDTH;
        
        itc_mapping_insert(t->page, t->as->asid, entry);
        
#ifdef CONFIG_VHPT
        vhpt_mapping_insert(t->page, t->as->asid, entry);
#endif
}

/** Instruction TLB fault handler for faults with VHPT turned off.
 *
 * @param vector Interruption vector.
 * @param istate Structure with saved interruption state.
 *
 */
void alternate_instruction_tlb_fault(uint64_t vector, istate_t *istate)
{
        region_register_t rr;
        rid_t rid;
        uintptr_t va;
        pte_t *t;
        
        va = istate->cr_ifa; /* faulting address */
        rr.word = rr_read(VA2VRN(va));
        rid = rr.map.rid;
        
        page_table_lock(AS, true);
        t = page_mapping_find(AS, va);
        if (t) {
                /*
                 * The mapping was found in software page hash table.
                 * Insert it into data translation cache.
                 */
                itc_pte_copy(t);
                page_table_unlock(AS, true);
        } else {
                /*
                 * Forward the page fault to address space page fault handler.
                 */
                page_table_unlock(AS, true);
                if (as_page_fault(va, PF_ACCESS_EXEC, istate) == AS_PF_FAULT) {
                        fault_if_from_uspace(istate, "Page fault at %p.", va);
                        panic_memtrap(istate, PF_ACCESS_EXEC, va,
                            "Page fault.");
                }
        }
}

static int is_io_page_accessible(int page)
{
        if (TASK->arch.iomap)
                return bitmap_get(TASK->arch.iomap, page);
        else
                return 0;
}

/**
 * There is special handling of memory mapped legacy io, because of 4KB sized
 * access for userspace.
 *
 * @param va     Virtual address of page fault.
 * @param istate Structure with saved interruption state.
 *
 * @return One on success, zero on failure.
 *
 */
static int try_memmap_io_insertion(uintptr_t va, istate_t *istate)
{
        if ((va >= IO_OFFSET ) && (va < IO_OFFSET + (1 << IO_PAGE_WIDTH))) {
                if (TASK) {
                        uint64_t io_page = (va & ((1 << IO_PAGE_WIDTH) - 1)) >>
                            USPACE_IO_PAGE_WIDTH;
                        
                        if (is_io_page_accessible(io_page)) {
                                uint64_t page, frame;
                                
                                page = IO_OFFSET +
                                    (1 << USPACE_IO_PAGE_WIDTH) * io_page;
                                frame = IO_FRAME_BASE +
                                    (1 << USPACE_IO_PAGE_WIDTH) * io_page;
                                
                                tlb_entry_t entry;
                                
                                entry.word[0] = 0;
                                entry.word[1] = 0;
                                
                                entry.p = true;             /* present */
                                entry.ma = MA_UNCACHEABLE;
                                entry.a = true;             /* already accessed */
                                entry.d = true;             /* already dirty */
                                entry.pl = PL_USER;
                                entry.ar = AR_READ | AR_WRITE;
                                entry.ppn = frame >> PPN_SHIFT;
                                entry.ps = USPACE_IO_PAGE_WIDTH;
                                
                                dtc_mapping_insert(page, TASK->as->asid, entry);
                                return 1;
                        } else {
                                fault_if_from_uspace(istate,
                                    "IO access fault at %p.", va);
                        }
                }
        }
        
        return 0;
}

/** Data TLB fault handler for faults with VHPT turned off.
 *
 * @param vector Interruption vector.
 * @param istate Structure with saved interruption state.
 *
 */
void alternate_data_tlb_fault(uint64_t vector, istate_t *istate)
{
        if (istate->cr_isr.sp) {
                /* Speculative load. Deffer the exception
                   until a more clever approach can be used.
                   
                   Currently if we try to find the mapping
                   for the speculative load while in the kernel,
                   we might introduce a livelock because of
                   the possibly invalid values of the address. */
                istate->cr_ipsr.ed = true;
                return;
        }
        
        uintptr_t va = istate->cr_ifa;  /* faulting address */
        
        region_register_t rr;
        rr.word = rr_read(VA2VRN(va));
        rid_t rid = rr.map.rid;
        if (RID2ASID(rid) == ASID_KERNEL) {
                if (VA2VRN(va) == VRN_KERNEL) {
                        /*
                         * Provide KA2PA(identity) mapping for faulting piece of
                         * kernel address space.
                         */
                        dtlb_kernel_mapping_insert(va, KA2PA(va), false, 0);
                        return;
                }
        }
        
        
        page_table_lock(AS, true);
        pte_t *entry = page_mapping_find(AS, va);
        if (entry) {
                /*
                 * The mapping was found in the software page hash table.
                 * Insert it into data translation cache.
                 */
                dtc_pte_copy(entry);
                page_table_unlock(AS, true);
        } else {
                page_table_unlock(AS, true);
                if (try_memmap_io_insertion(va, istate))
                        return;
                
                /*
                 * Forward the page fault to the address space page fault
                 * handler.
                 */
                if (as_page_fault(va, PF_ACCESS_READ, istate) == AS_PF_FAULT) {
                        fault_if_from_uspace(istate, "Page fault at %p.", va);
                        panic_memtrap(istate, PF_ACCESS_READ, va,
                            "Page fault.");
                }
        }
}

/** Data nested TLB fault handler.
 *
 * This fault should not occur.
 *
 * @param vector Interruption vector.
 * @param istate Structure with saved interruption state.
 *
 */
void data_nested_tlb_fault(uint64_t vector, istate_t *istate)
{
        ASSERT(false);
}

/** Data Dirty bit fault handler.
 *
 * @param vector Interruption vector.
 * @param istate Structure with saved interruption state.
 *
 */
void data_dirty_bit_fault(uint64_t vector, istate_t *istate)
{
        region_register_t rr;
        rid_t rid;
        uintptr_t va;
        pte_t *t;
        
        va = istate->cr_ifa;  /* faulting address */
        rr.word = rr_read(VA2VRN(va));
        rid = rr.map.rid;
        
        page_table_lock(AS, true);
        t = page_mapping_find(AS, va);
        ASSERT((t) && (t->p));
        if ((t) && (t->p) && (t->w)) {
                /*
                 * Update the Dirty bit in page tables and reinsert
                 * the mapping into DTC.
                 */
                t->d = true;
                dtc_pte_copy(t);
        } else {
                if (as_page_fault(va, PF_ACCESS_WRITE, istate) == AS_PF_FAULT) {
                        fault_if_from_uspace(istate, "Page fault at %p.", va);
                        panic_memtrap(istate, PF_ACCESS_WRITE, va,
                            "Page fault.");
                }
        }
        page_table_unlock(AS, true);
}

/** Instruction access bit fault handler.
 *
 * @param vector Interruption vector.
 * @param istate Structure with saved interruption state.
 *
 */
void instruction_access_bit_fault(uint64_t vector, istate_t *istate)
{
        region_register_t rr;
        rid_t rid;
        uintptr_t va;
        pte_t *t;
        
        va = istate->cr_ifa;  /* faulting address */
        rr.word = rr_read(VA2VRN(va));
        rid = rr.map.rid;
        
        page_table_lock(AS, true);
        t = page_mapping_find(AS, va);
        ASSERT((t) && (t->p));
        if ((t) && (t->p) && (t->x)) {
                /*
                 * Update the Accessed bit in page tables and reinsert
                 * the mapping into ITC.
                 */
                t->a = true;
                itc_pte_copy(t);
        } else {
                if (as_page_fault(va, PF_ACCESS_EXEC, istate) == AS_PF_FAULT) {
                        fault_if_from_uspace(istate, "Page fault at %p.", va);
                        panic_memtrap(istate, PF_ACCESS_EXEC, va,
                            "Page fault.");
                }
        }
        page_table_unlock(AS, true);
}

/** Data access bit fault handler.
 *
 * @param vector Interruption vector.
 * @param istate Structure with saved interruption state.
 *
 */
void data_access_bit_fault(uint64_t vector, istate_t *istate)
{
        region_register_t rr;
        rid_t rid;
        uintptr_t va;
        pte_t *t;
        
        va = istate->cr_ifa;  /* faulting address */
        rr.word = rr_read(VA2VRN(va));
        rid = rr.map.rid;
        
        page_table_lock(AS, true);
        t = page_mapping_find(AS, va);
        ASSERT((t) && (t->p));
        if ((t) && (t->p)) {
                /*
                 * Update the Accessed bit in page tables and reinsert
                 * the mapping into DTC.
                 */
                t->a = true;
                dtc_pte_copy(t);
        } else {
                if (as_page_fault(va, PF_ACCESS_READ, istate) == AS_PF_FAULT) {
                        fault_if_from_uspace(istate, "Page fault at %p.", va);
                        panic_memtrap(istate, PF_ACCESS_READ, va,
                            "Page fault.");
                }
        }
        page_table_unlock(AS, true);
}

/** Data access rights fault handler.
 *
 * @param vector Interruption vector.
 * @param istate Structure with saved interruption state.
 *
 */
void data_access_rights_fault(uint64_t vector, istate_t *istate)
{
        region_register_t rr;
        rid_t rid;
        uintptr_t va;
        pte_t *t;
        
        va = istate->cr_ifa;  /* faulting address */
        rr.word = rr_read(VA2VRN(va));
        rid = rr.map.rid;
        
        /*
         * Assume a write to a read-only page.
         */
        page_table_lock(AS, true);
        t = page_mapping_find(AS, va);
        ASSERT((t) && (t->p));
        ASSERT(!t->w);
        if (as_page_fault(va, PF_ACCESS_WRITE, istate) == AS_PF_FAULT) {
                fault_if_from_uspace(istate, "Page fault at %p.", va);
                panic_memtrap(istate, PF_ACCESS_WRITE, va, "Page fault.");
        }
        page_table_unlock(AS, true);
}

/** Page not present fault handler.
 *
 * @param vector Interruption vector.
 * @param istate Structure with saved interruption state.
 *
 */
void page_not_present(uint64_t vector, istate_t *istate)
{
        region_register_t rr;
        rid_t rid;
        uintptr_t va;
        pte_t *t;
        
        va = istate->cr_ifa;  /* faulting address */
        rr.word = rr_read(VA2VRN(va));
        rid = rr.map.rid;
        
        page_table_lock(AS, true);
        t = page_mapping_find(AS, va);
        ASSERT(t);
        
        if (t->p) {
                /*
                 * If the Present bit is set in page hash table, just copy it
                 * and update ITC/DTC.
                 */
                if (t->x)
                        itc_pte_copy(t);
                else
                        dtc_pte_copy(t);
                page_table_unlock(AS, true);
        } else {
                page_table_unlock(AS, true);
                if (as_page_fault(va, PF_ACCESS_READ, istate) == AS_PF_FAULT) {
                        fault_if_from_uspace(istate, "Page fault at %p.", va);
                        panic_memtrap(istate, PF_ACCESS_READ, va,
                            "Page fault.");
                }
        }
}

void tlb_arch_init(void)
{
}

void tlb_print(void)
{
}

/** @}
 */