source: mainline/kernel/arch/ppc32/src/mm/pht.c

/*
 * Copyright (c) 2006 Martin Decky
 * 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 kernel_ppc32_mm
 * @{
 */
/** @file
 */

#include <arch/mm/pht.h>
#include <arch/mm/tlb.h>
#include <assert.h>
#include <interrupt.h>
#include <mm/as.h>
#include <mm/page.h>
#include <macros.h>
#include <typedefs.h>

static unsigned int seed = 42;

/** Try to find PTE for faulting address
 *
 * @param as       Address space.
 * @param badvaddr Faulting virtual address.
 * @param access   Access mode that caused the fault.
 * @param istate   Pointer to interrupted state.
 * @param[out] pte Structure that will receive a copy of the found PTE.
 *
 * @return True if the mapping was found, false otherwise.
 *
 */
static bool find_mapping_and_check(as_t *as, uintptr_t badvaddr, int access,
    istate_t *istate, pte_t *pte)
{
        /*
         * Check if the mapping exists in page tables.
         */
        bool found = page_mapping_find(as, badvaddr, true, pte);
        if (found && pte->present) {
                /*
                 * Mapping found in page tables.
                 * Immediately succeed.
                 */
                return true;
        }
        /*
         * Mapping not found in page tables.
         * Resort to higher-level page fault handler.
         */
        if (as_page_fault(badvaddr, access, istate) == AS_PF_OK) {
                /*
                 * The higher-level page fault handler succeeded,
                 * The mapping ought to be in place.
                 */
                found = page_mapping_find(as, badvaddr, true, pte);

                assert(found);
                assert(pte->present);

                return found;
        }

        return false;
}

static void pht_insert(const uintptr_t vaddr, const pte_t *pte)
{
        uint32_t page = (vaddr >> 12) & 0xffff;
        uint32_t api = (vaddr >> 22) & 0x3f;

        uint32_t vsid = sr_get(vaddr);
        uint32_t sdr1 = sdr1_get();

        // FIXME: compute size of PHT exactly
        phte_t *phte = (phte_t *) PA2KA(sdr1 & 0xffff0000);

        /* Primary hash (xor) */
        uint32_t h = 0;
        uint32_t hash = vsid ^ page;
        uint32_t base = (hash & 0x3ff) << 3;
        uint32_t i;
        bool found = false;

        /* Find colliding PTE in PTEG */
        for (i = 0; i < 8; i++) {
                if ((phte[base + i].v) &&
                    (phte[base + i].vsid == vsid) &&
                    (phte[base + i].api == api) &&
                    (phte[base + i].h == 0)) {
                        found = true;
                        break;
                }
        }

        if (!found) {
                /* Find unused PTE in PTEG */
                for (i = 0; i < 8; i++) {
                        if (!phte[base + i].v) {
                                found = true;
                                break;
                        }
                }
        }

        if (!found) {
                /* Secondary hash (not) */
                uint32_t base2 = (~hash & 0x3ff) << 3;

                /* Find colliding PTE in PTEG */
                for (i = 0; i < 8; i++) {
                        if ((phte[base2 + i].v) &&
                            (phte[base2 + i].vsid == vsid) &&
                            (phte[base2 + i].api == api) &&
                            (phte[base2 + i].h == 1)) {
                                found = true;
                                base = base2;
                                h = 1;
                                break;
                        }
                }

                if (!found) {
                        /* Find unused PTE in PTEG */
                        for (i = 0; i < 8; i++) {
                                if (!phte[base2 + i].v) {
                                        found = true;
                                        base = base2;
                                        h = 1;
                                        break;
                                }
                        }
                }

                if (!found)
                        i = RANDI(seed) % 8;
        }

        phte[base + i].v = 1;
        phte[base + i].vsid = vsid;
        phte[base + i].h = h;
        phte[base + i].api = api;
        phte[base + i].rpn = pte->pfn;
        phte[base + i].r = 0;
        phte[base + i].c = 0;
        phte[base + i].wimg = (pte->page_cache_disable ? WIMG_NO_CACHE : 0);
        phte[base + i].pp = 2; // FIXME
}

/** Process Instruction/Data Storage Exception
 *
 * @param n      Exception vector number.
 * @param istate Interrupted register context.
 *
 */
void pht_refill(unsigned int n, istate_t *istate)
{
        uintptr_t badvaddr;

        if (n == VECTOR_DATA_STORAGE)
                badvaddr = istate->dar;
        else
                badvaddr = istate->pc;

        pte_t pte;
        bool found = find_mapping_and_check(AS, badvaddr,
            PF_ACCESS_READ /* FIXME */, istate, &pte);

        if (found) {
                /* Record access to PTE */
                pte.accessed = 1;
                pht_insert(badvaddr, &pte);
        }
}

void pht_invalidate(as_t *as, uintptr_t page, size_t pages)
{
        uint32_t sdr1 = sdr1_get();

        // FIXME: compute size of PHT exactly
        phte_t *phte = (phte_t *) PA2KA(sdr1 & 0xffff0000);

        // FIXME: this invalidates all PHT entries,
        // which is an overkill, invalidate only
        // selectively
        for (size_t i = 0; i < 8192; i++) {
                phte[i].v = 0;
        }
}

/** @}
 */