[apple/xnu.git] / osfmk / x86_64 / pmap_pcid.c

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 * Please obtain a copy of the License at
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#include <i386/proc_reg.h>
#include <i386/cpuid.h>
#include <i386/tsc.h>
#include <vm/pmap.h>
#include <vm/vm_map.h>
#include <i386/pmap_internal.h>
#include <i386/pmap_pcid.h>
#include <mach/branch_predicates.h>

/*
 * PCID (Process context identifier) aka tagged TLB support.
 * On processors with this feature, unless disabled via the -pmap_pcid_disable
 * boot-arg, the following algorithm is in effect:
 * Each processor maintains an array of tag refcounts indexed by tag.
 * Each address space maintains an array of tags indexed by CPU number.
 * Each address space maintains a coherency vector, indexed by CPU
 * indicating that the TLB state for that address space has a pending
 * invalidation.
 * On a context switch, a refcounted tag is lazily assigned to the newly
 * dispatched (CPU, address space) tuple.
 * When an inactive address space is invalidated on a remote CPU, it is marked
 * for invalidation upon the next dispatch. Some invalidations are
 * also processed at the user/kernel boundary.
 * Provisions are made for the case where a CPU is overcommmitted, i.e.
 * more active address spaces exist than the number of logical tags
 * provided for by the processor architecture (currently 4096).
 * The algorithm assumes the processor remaps the logical tags
 * to physical TLB context IDs in an LRU fashion for efficiency. (DRK '10)
 */

uint32_t        pmap_pcid_ncpus;
boolean_t       pmap_pcid_disabled = FALSE;

void    pmap_pcid_configure(void) {
        int ccpu = cpu_number();
        uintptr_t cr4 = get_cr4();
        boolean_t pcid_present = FALSE;

        pmap_pcid_log("PCID configure invoked on CPU %d\n", ccpu);
        pmap_assert(ml_get_interrupts_enabled() == FALSE || get_preemption_level() !=0);
        pmap_assert(cpu_mode_is64bit());

        if (PE_parse_boot_argn("-pmap_pcid_disable", &pmap_pcid_disabled, sizeof (pmap_pcid_disabled))) {
                pmap_pcid_log("PMAP: PCID feature disabled\n");
                printf("PMAP: PCID feature disabled, %u\n", pmap_pcid_disabled);
                kprintf("PMAP: PCID feature disabled %u\n", pmap_pcid_disabled);
        }
         /* no_shared_cr3+PCID is currently unsupported */
#if     DEBUG
        if (pmap_pcid_disabled == FALSE)
                no_shared_cr3 = FALSE;
        else
                no_shared_cr3 = TRUE;
#else
        if (no_shared_cr3)
                pmap_pcid_disabled = TRUE;
#endif
        if (pmap_pcid_disabled || no_shared_cr3) {
                unsigned i;
                /* Reset PCID status, as we may have picked up
                 * strays if discovered prior to platform
                 * expert initialization.
                 */
                for (i = 0; i < real_ncpus; i++) {
                        if (cpu_datap(i)) {
                                cpu_datap(i)->cpu_pmap_pcid_enabled = FALSE;
                        }
                        pmap_pcid_ncpus = 0;
                }
                cpu_datap(ccpu)->cpu_pmap_pcid_enabled = FALSE;
                return;
        }
        /* DRKTODO: assert if features haven't been discovered yet. Redundant
         * invocation of cpu_mode_init and descendants masks this for now.
         */
        if ((cpuid_features() & CPUID_FEATURE_PCID))
                pcid_present = TRUE;
        else {
                cpu_datap(ccpu)->cpu_pmap_pcid_enabled = FALSE;
                pmap_pcid_log("PMAP: PCID not detected CPU %d\n", ccpu);
                return;
        }
        if ((cr4 & (CR4_PCIDE | CR4_PGE)) == (CR4_PCIDE|CR4_PGE)) {
                cpu_datap(ccpu)->cpu_pmap_pcid_enabled = TRUE;
                pmap_pcid_log("PMAP: PCID already enabled %d\n", ccpu);
                return;
        }
        if (pcid_present == TRUE) {
                pmap_pcid_log("Pre-PCID:CR0: 0x%lx, CR3: 0x%lx, CR4(CPU %d): 0x%lx\n", get_cr0(), get_cr3_raw(), ccpu, cr4);

                if (cpu_number() >= PMAP_PCID_MAX_CPUS) {
                        panic("PMAP_PCID_MAX_CPUS %d\n", cpu_number());
                }
                if ((get_cr4() & CR4_PGE) == 0) {
                        set_cr4(get_cr4() | CR4_PGE);
                        pmap_pcid_log("Toggled PGE ON (CPU: %d\n", ccpu);
                }
                set_cr4(get_cr4() | CR4_PCIDE);
                pmap_pcid_log("Post PCID: CR0: 0x%lx, CR3: 0x%lx, CR4(CPU %d): 0x%lx\n", get_cr0(), get_cr3_raw(), ccpu, get_cr4());
                tlb_flush_global();
                cpu_datap(ccpu)->cpu_pmap_pcid_enabled = TRUE;

                if (OSIncrementAtomic(&pmap_pcid_ncpus) == machine_info.max_cpus) {
                        pmap_pcid_log("All PCIDs enabled: real_ncpus: %d, pmap_pcid_ncpus: %d\n", real_ncpus, pmap_pcid_ncpus);
                }
                cpu_datap(ccpu)->cpu_pmap_pcid_coherentp =
                    cpu_datap(ccpu)->cpu_pmap_pcid_coherentp_kernel =
                    &(kernel_pmap->pmap_pcid_coherency_vector[ccpu]);
                cpu_datap(ccpu)->cpu_pcid_refcounts[0] = 1;
        }
}

void pmap_pcid_initialize(pmap_t p) {
        unsigned i;
        unsigned nc = sizeof(p->pmap_pcid_cpus)/sizeof(pcid_t);

        pmap_assert(nc >= real_ncpus);
        for (i = 0; i < nc; i++) {
                p->pmap_pcid_cpus[i] = PMAP_PCID_INVALID_PCID;
                /* We assume here that the coherency vector is zeroed by
                 * pmap_create
                 */
        }
}

void pmap_pcid_initialize_kernel(pmap_t p) {
        unsigned i;
        unsigned nc = sizeof(p->pmap_pcid_cpus)/sizeof(pcid_t);

        for (i = 0; i < nc; i++) {
                p->pmap_pcid_cpus[i] = 0;
                /* We assume here that the coherency vector is zeroed by
                 * pmap_create
                 */
        }
}

pcid_t  pmap_pcid_allocate_pcid(int ccpu) {
        int i;
        pcid_ref_t      cur_min = 0xFF;
        uint32_t        cur_min_index = ~1;
        pcid_ref_t      *cpu_pcid_refcounts = &cpu_datap(ccpu)->cpu_pcid_refcounts[0];
        pcid_ref_t      old_count;

        if ((i = cpu_datap(ccpu)->cpu_pcid_free_hint) != 0) {
                if (cpu_pcid_refcounts[i] == 0) {
                        (void)__sync_fetch_and_add(&cpu_pcid_refcounts[i], 1);
                        cpu_datap(ccpu)->cpu_pcid_free_hint = 0;
                        return i;
                }
        }
        /* Linear scan to discover free slot, with hint. Room for optimization
         * but with intelligent prefetchers this should be
         * adequately performant, as it is invoked
         * only on first dispatch of a new address space onto
         * a given processor. DRKTODO: use larger loads and
         * zero byte discovery -- any pattern != ~1 should
         * signify a free slot.
         */
        for (i = PMAP_PCID_MIN_PCID; i < PMAP_PCID_MAX_PCID; i++) {
                pcid_ref_t cur_refcount = cpu_pcid_refcounts[i];

                pmap_assert(cur_refcount < PMAP_PCID_MAX_REFCOUNT);

                if (cur_refcount == 0) {
                        (void)__sync_fetch_and_add(&cpu_pcid_refcounts[i], 1);
                        return i;
                }
                else {
                        if (cur_refcount < cur_min) {
                                cur_min_index = i;
                                cur_min = cur_refcount;
                        }
                }
        }
        pmap_assert(cur_min_index > 0 && cur_min_index < PMAP_PCID_MAX_PCID);
        /* Consider "rebalancing" tags actively in highly oversubscribed cases
         * perhaps selecting tags with lower activity.
         */

        old_count = __sync_fetch_and_add(&cpu_pcid_refcounts[cur_min_index], 1);
        pmap_assert(old_count < PMAP_PCID_MAX_REFCOUNT);
        return cur_min_index;
}

void    pmap_pcid_deallocate_pcid(int ccpu, pmap_t tpmap) {
        pcid_t pcid;
        pmap_t lp;
        pcid_ref_t prior_count;

        pcid = tpmap->pmap_pcid_cpus[ccpu];
        pmap_assert(pcid != PMAP_PCID_INVALID_PCID);
        if (pcid == PMAP_PCID_INVALID_PCID)
                return;

        lp = cpu_datap(ccpu)->cpu_pcid_last_pmap_dispatched[pcid];
        pmap_assert(pcid > 0 && pcid < PMAP_PCID_MAX_PCID);
        pmap_assert(cpu_datap(ccpu)->cpu_pcid_refcounts[pcid] >= 1);

        if (lp == tpmap)
                (void)__sync_bool_compare_and_swap(&cpu_datap(ccpu)->cpu_pcid_last_pmap_dispatched[pcid], tpmap, PMAP_INVALID);

        if ((prior_count = __sync_fetch_and_sub(&cpu_datap(ccpu)->cpu_pcid_refcounts[pcid], 1)) == 1) {
                    cpu_datap(ccpu)->cpu_pcid_free_hint = pcid;
        }
        pmap_assert(prior_count <= PMAP_PCID_MAX_REFCOUNT);
}

void    pmap_destroy_pcid_sync(pmap_t p) {
        int i;
        pmap_assert(ml_get_interrupts_enabled() == FALSE || get_preemption_level() !=0);
        for (i = 0; i < PMAP_PCID_MAX_CPUS; i++)
                if (p->pmap_pcid_cpus[i] != PMAP_PCID_INVALID_PCID)
                        pmap_pcid_deallocate_pcid(i, p);
}

pcid_t  pcid_for_pmap_cpu_tuple(pmap_t pmap, int ccpu) {
        return pmap->pmap_pcid_cpus[ccpu];
}
#if PMAP_ASSERT
#define PCID_RECORD_SIZE 128
uint64_t pcid_record_array[PCID_RECORD_SIZE];
#endif

void    pmap_pcid_activate(pmap_t tpmap, int ccpu) {
        pcid_t          new_pcid = tpmap->pmap_pcid_cpus[ccpu];
        pmap_t          last_pmap;
        boolean_t       pcid_conflict = FALSE, pending_flush = FALSE;

        pmap_assert(cpu_datap(ccpu)->cpu_pmap_pcid_enabled);
        if (__improbable(new_pcid == PMAP_PCID_INVALID_PCID)) {
                new_pcid = tpmap->pmap_pcid_cpus[ccpu] = pmap_pcid_allocate_pcid(ccpu);
        }
        pmap_assert(new_pcid != PMAP_PCID_INVALID_PCID);
#ifdef  PCID_ASSERT     
        cpu_datap(ccpu)->cpu_last_pcid = cpu_datap(ccpu)->cpu_active_pcid;
#endif
        cpu_datap(ccpu)->cpu_active_pcid = new_pcid;

        pending_flush = (tpmap->pmap_pcid_coherency_vector[ccpu] != 0);
        if (__probable(pending_flush == FALSE)) {
                last_pmap = cpu_datap(ccpu)->cpu_pcid_last_pmap_dispatched[new_pcid];
                pcid_conflict = ((last_pmap != NULL) &&(tpmap != last_pmap));
        }
        if (__improbable(pending_flush || pcid_conflict)) {
                pmap_pcid_validate_cpu(tpmap, ccpu);
        }
        /* Consider making this a unique id */
        cpu_datap(ccpu)->cpu_pcid_last_pmap_dispatched[new_pcid] = tpmap;

        pmap_assert(new_pcid < PMAP_PCID_MAX_PCID);
        pmap_assert(((tpmap ==  kernel_pmap) && new_pcid == 0) || ((new_pcid != PMAP_PCID_INVALID_PCID) && (new_pcid != 0)));
#if     PMAP_ASSERT
        pcid_record_array[ccpu % PCID_RECORD_SIZE] = tpmap->pm_cr3 | new_pcid | (((uint64_t)(!(pending_flush || pcid_conflict))) <<63);
        pml4_entry_t *pml4 = pmap64_pml4(tpmap, 0ULL);
        /* Diagnostic to detect pagetable anchor corruption */
        if (pml4[KERNEL_PML4_INDEX] != kernel_pmap->pm_pml4[KERNEL_PML4_INDEX])
                __asm__ volatile("int3");
#endif  /* PMAP_ASSERT */
        set_cr3_composed(tpmap->pm_cr3, new_pcid, !(pending_flush || pcid_conflict));

        if (!pending_flush) {
                /* We did not previously observe a pending invalidation for this
                 * ASID. However, the load from the coherency vector
                 * could've been reordered ahead of the store to the
                 * active_cr3 field (in the context switch path, our
                 * caller). Re-consult the pending invalidation vector
                 * after the CR3 write. We rely on MOV CR3's documented
                 * serializing property to avoid insertion of an expensive
                 * barrier. (DRK)
                 */
                pending_flush = (tpmap->pmap_pcid_coherency_vector[ccpu] != 0);
                if (__improbable(pending_flush != 0)) {
                        pmap_pcid_validate_cpu(tpmap, ccpu);
                        set_cr3_composed(tpmap->pm_cr3, new_pcid, FALSE);
                }
        }
        cpu_datap(ccpu)->cpu_pmap_pcid_coherentp = &(tpmap->pmap_pcid_coherency_vector[ccpu]);
#if     DEBUG   
        KERNEL_DEBUG_CONSTANT(0x9c1d0000, tpmap, new_pcid, pending_flush, pcid_conflict, 0);
#endif
}