// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * SN Platform GRU Driver
 *
 *              KERNEL SERVICES THAT USE THE GRU
 *
 *  Copyright (c) 2008 Silicon Graphics, Inc.  All Rights Reserved.
 */

#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/slab.h>
#include <linux/mm.h>
#include <linux/spinlock.h>
#include <linux/device.h>
#include <linux/miscdevice.h>
#include <linux/proc_fs.h>
#include <linux/interrupt.h>
#include <linux/sync_core.h>
#include <linux/uaccess.h>
#include <linux/delay.h>
#include <linux/export.h>
#include <asm/io_apic.h>
#include "gru.h"
#include "grulib.h"
#include "grutables.h"
#include "grukservices.h"
#include "gru_instructions.h"
#include <asm/uv/uv_hub.h>

/*
 * Kernel GRU Usage
 *
 * The following is an interim algorithm for management of kernel GRU
 * resources. This will likely be replaced when we better understand the
 * kernel/user requirements.
 *
 * Blade percpu resources reserved for kernel use. These resources are
 * reserved whenever the kernel context for the blade is loaded. Note
 * that the kernel context is not guaranteed to be always available. It is
 * loaded on demand & can be stolen by a user if the user demand exceeds the
 * kernel demand. The kernel can always reload the kernel context but
 * a SLEEP may be required!!!.
 *
 * Async Overview:
 *
 *      Each blade has one "kernel context" that owns GRU kernel resources
 *      located on the blade. Kernel drivers use GRU resources in this context
 *      for sending messages, zeroing memory, etc.
 *
 *      The kernel context is dynamically loaded on demand. If it is not in
 *      use by the kernel, the kernel context can be unloaded & given to a user.
 *      The kernel context will be reloaded when needed. This may require that
 *      a context be stolen from a user.
 *              NOTE: frequent unloading/reloading of the kernel context is
 *              expensive. We are depending on batch schedulers, cpusets, sane
 *              drivers or some other mechanism to prevent the need for frequent
 *              stealing/reloading.
 *
 *      The kernel context consists of two parts:
 *              - 1 CB & a few DSRs that are reserved for each cpu on the blade.
 *                Each cpu has it's own private resources & does not share them
 *                with other cpus. These resources are used serially, ie,
 *                locked, used & unlocked  on each call to a function in
 *                grukservices.
 *                      (Now that we have dynamic loading of kernel contexts, I
 *                       may rethink this & allow sharing between cpus....)
 *
 *              - Additional resources can be reserved long term & used directly
 *                by UV drivers located in the kernel. Drivers using these GRU
 *                resources can use asynchronous GRU instructions that send
 *                interrupts on completion.
 *                      - these resources must be explicitly locked/unlocked
 *                      - locked resources prevent (obviously) the kernel
 *                        context from being unloaded.
 *                      - drivers using these resource directly issue their own
 *                        GRU instruction and must wait/check completion.
 *
 *                When these resources are reserved, the caller can optionally
 *                associate a wait_queue with the resources and use asynchronous
 *                GRU instructions. When an async GRU instruction completes, the
 *                driver will do a wakeup on the event.
 *
 */


#define ASYNC_HAN_TO_BID(h)     ((h) - 1)
#define ASYNC_BID_TO_HAN(b)     ((b) + 1)
#define ASYNC_HAN_TO_BS(h)      gru_base[ASYNC_HAN_TO_BID(h)]

#define GRU_NUM_KERNEL_CBR      1
#define GRU_NUM_KERNEL_DSR_BYTES 256
#define GRU_NUM_KERNEL_DSR_CL   (GRU_NUM_KERNEL_DSR_BYTES /             \
                                        GRU_CACHE_LINE_BYTES)

/* GRU instruction attributes for all instructions */
#define IMA                     IMA_CB_DELAY

/* GRU cacheline size is always 64 bytes - even on arches with 128 byte lines */
#define __gru_cacheline_aligned__                               \
        __attribute__((__aligned__(GRU_CACHE_LINE_BYTES)))

#define MAGIC   0x1234567887654321UL

/* Default retry count for GRU errors on kernel instructions */
#define EXCEPTION_RETRY_LIMIT   3

/* Status of message queue sections */
#define MQS_EMPTY               0
#define MQS_FULL                1
#define MQS_NOOP                2

/*----------------- RESOURCE MANAGEMENT -------------------------------------*/
/* optimized for x86_64 */
struct message_queue {
        union gru_mesqhead      head __gru_cacheline_aligned__; /* CL 0 */
        int                     qlines;                         /* DW 1 */
        long                    hstatus[2];
        void                    *next __gru_cacheline_aligned__;/* CL 1 */
        void                    *limit;
        void                    *start;
        void                    *start2;
        char                    data ____cacheline_aligned;     /* CL 2 */
};

/* First word in every message - used by mesq interface */
struct message_header {
        char    present;
        char    present2;
        char    lines;
        char    fill;
};

#define HSTATUS(mq, h)  ((mq) + offsetof(struct message_queue, hstatus[h]))

/*
 * Reload the blade's kernel context into a GRU chiplet. Called holding
 * the bs_kgts_sema for READ. Will steal user contexts if necessary.
 */
static void gru_load_kernel_context(struct gru_blade_state *bs, int blade_id)
{
        struct gru_state *gru;
        struct gru_thread_state *kgts;
        void *vaddr;
        int ctxnum, ncpus;

        up_read(&bs->bs_kgts_sema);
        down_write(&bs->bs_kgts_sema);

        if (!bs->bs_kgts) {
                do {
                        bs->bs_kgts = gru_alloc_gts(NULL, 0, 0, 0, 0, 0);
                        if (!IS_ERR(bs->bs_kgts))
                                break;
                        msleep(1);
                } while (true);
                bs->bs_kgts->ts_user_blade_id = blade_id;
        }
        kgts = bs->bs_kgts;

        if (!kgts->ts_gru) {
                STAT(load_kernel_context);
                ncpus = uv_blade_nr_possible_cpus(blade_id);
                kgts->ts_cbr_au_count = GRU_CB_COUNT_TO_AU(
                        GRU_NUM_KERNEL_CBR * ncpus + bs->bs_async_cbrs);
                kgts->ts_dsr_au_count = GRU_DS_BYTES_TO_AU(
                        GRU_NUM_KERNEL_DSR_BYTES * ncpus +
                                bs->bs_async_dsr_bytes);
                while (!gru_assign_gru_context(kgts)) {
                        msleep(1);
                        gru_steal_context(kgts);
                }
                gru_load_context(kgts);
                gru = bs->bs_kgts->ts_gru;
                vaddr = gru->gs_gru_base_vaddr;
                ctxnum = kgts->ts_ctxnum;
                bs->kernel_cb = get_gseg_base_address_cb(vaddr, ctxnum, 0);
                bs->kernel_dsr = get_gseg_base_address_ds(vaddr, ctxnum, 0);
        }
        downgrade_write(&bs->bs_kgts_sema);
}

/*
 * Free all kernel contexts that are not currently in use.
 *   Returns 0 if all freed, else number of inuse context.
 */
static int gru_free_kernel_contexts(void)
{
        struct gru_blade_state *bs;
        struct gru_thread_state *kgts;
        int bid, ret = 0;

        for (bid = 0; bid < GRU_MAX_BLADES; bid++) {
                bs = gru_base[bid];
                if (!bs)
                        continue;

                /* Ignore busy contexts. Don't want to block here.  */
                if (down_write_trylock(&bs->bs_kgts_sema)) {
                        kgts = bs->bs_kgts;
                        if (kgts && kgts->ts_gru)
                                gru_unload_context(kgts, 0);
                        bs->bs_kgts = NULL;
                        up_write(&bs->bs_kgts_sema);
                        kfree(kgts);
                } else {
                        ret++;
                }
        }
        return ret;
}

/*
 * Lock & load the kernel context for the specified blade.
 */
static struct gru_blade_state *gru_lock_kernel_context(int blade_id)
{
        struct gru_blade_state *bs;
        int bid;

        STAT(lock_kernel_context);
again:
        bid = blade_id < 0 ? uv_numa_blade_id() : blade_id;
        bs = gru_base[bid];

        /* Handle the case where migration occurred while waiting for the sema */
        down_read(&bs->bs_kgts_sema);
        if (blade_id < 0 && bid != uv_numa_blade_id()) {
                up_read(&bs->bs_kgts_sema);
                goto again;
        }
        if (!bs->bs_kgts || !bs->bs_kgts->ts_gru)
                gru_load_kernel_context(bs, bid);
        return bs;

}

/*
 * Unlock the kernel context for the specified blade. Context is not
 * unloaded but may be stolen before next use.
 */
static void gru_unlock_kernel_context(int blade_id)
{
        struct gru_blade_state *bs;

        bs = gru_base[blade_id];
        up_read(&bs->bs_kgts_sema);
        STAT(unlock_kernel_context);
}

/*
 * Reserve & get pointers to the DSR/CBRs reserved for the current cpu.
 *      - returns with preemption disabled
 */
static int gru_get_cpu_resources(int dsr_bytes, void **cb, void **dsr)
{
        struct gru_blade_state *bs;
        int lcpu;

        BUG_ON(dsr_bytes > GRU_NUM_KERNEL_DSR_BYTES);
        bs = gru_lock_kernel_context(-1);
        lcpu = uv_blade_processor_id();
        *cb = bs->kernel_cb + lcpu * GRU_HANDLE_STRIDE;
        *dsr = bs->kernel_dsr + lcpu * GRU_NUM_KERNEL_DSR_BYTES;
        return 0;
}

/*
 * Free the current cpus reserved DSR/CBR resources.
 */
static void gru_free_cpu_resources(void *cb, void *dsr)
{
        gru_unlock_kernel_context(uv_numa_blade_id());
}

/*
 * Reserve GRU resources to be used asynchronously.
 *   Note: currently supports only 1 reservation per blade.
 *
 *      input:
 *              blade_id  - blade on which resources should be reserved
 *              cbrs      - number of CBRs
 *              dsr_bytes - number of DSR bytes needed
 *      output:
 *              handle to identify resource
 *              (0 = async resources already reserved)
 */
unsigned long gru_reserve_async_resources(int blade_id, int cbrs, int dsr_bytes,
                        struct completion *cmp)
{
        struct gru_blade_state *bs;
        struct gru_thread_state *kgts;
        int ret = 0;

        bs = gru_base[blade_id];

        down_write(&bs->bs_kgts_sema);

        /* Verify no resources already reserved */
        if (bs->bs_async_dsr_bytes + bs->bs_async_cbrs)
                goto done;
        bs->bs_async_dsr_bytes = dsr_bytes;
        bs->bs_async_cbrs = cbrs;
        bs->bs_async_wq = cmp;
        kgts = bs->bs_kgts;

        /* Resources changed. Unload context if already loaded */
        if (kgts && kgts->ts_gru)
                gru_unload_context(kgts, 0);
        ret = ASYNC_BID_TO_HAN(blade_id);

done:
        up_write(&bs->bs_kgts_sema);
        return ret;
}

/*
 * Release async resources previously reserved.
 *
 *      input:
 *              han - handle to identify resources
 */
void gru_release_async_resources(unsigned long han)
{
        struct gru_blade_state *bs = ASYNC_HAN_TO_BS(han);

        down_write(&bs->bs_kgts_sema);
        bs->bs_async_dsr_bytes = 0;
        bs->bs_async_cbrs = 0;
        bs->bs_async_wq = NULL;
        up_write(&bs->bs_kgts_sema);
}

/*
 * Wait for async GRU instructions to complete.
 *
 *      input:
 *              han - handle to identify resources
 */
void gru_wait_async_cbr(unsigned long han)
{
        struct gru_blade_state *bs = ASYNC_HAN_TO_BS(han);

        wait_for_completion(bs->bs_async_wq);
        mb();
}

/*
 * Lock previous reserved async GRU resources
 *
 *      input:
 *              han - handle to identify resources
 *      output:
 *              cb  - pointer to first CBR
 *              dsr - pointer to first DSR
 */
void gru_lock_async_resource(unsigned long han,  void **cb, void **dsr)
{
        struct gru_blade_state *bs = ASYNC_HAN_TO_BS(han);
        int blade_id = ASYNC_HAN_TO_BID(han);
        int ncpus;

        gru_lock_kernel_context(blade_id);
        ncpus = uv_blade_nr_possible_cpus(blade_id);
        if (cb)
                *cb = bs->kernel_cb + ncpus * GRU_HANDLE_STRIDE;
        if (dsr)
                *dsr = bs->kernel_dsr + ncpus * GRU_NUM_KERNEL_DSR_BYTES;
}

/*
 * Unlock previous reserved async GRU resources
 *
 *      input:
 *              han - handle to identify resources
 */
void gru_unlock_async_resource(unsigned long han)
{
        int blade_id = ASYNC_HAN_TO_BID(han);

        gru_unlock_kernel_context(blade_id);
}

/*----------------------------------------------------------------------*/
int gru_get_cb_exception_detail(void *cb,
                struct control_block_extended_exc_detail *excdet)
{
        struct gru_control_block_extended *cbe;
        struct gru_thread_state *kgts = NULL;
        unsigned long off;
        int cbrnum, bid;

        /*
         * Locate kgts for cb. This algorithm is SLOW but
         * this function is rarely called (ie., almost never).
         * Performance does not matter.
         */
        for_each_possible_blade(bid) {
                if (!gru_base[bid])
                        break;
                kgts = gru_base[bid]->bs_kgts;
                if (!kgts || !kgts->ts_gru)
                        continue;
                off = cb - kgts->ts_gru->gs_gru_base_vaddr;
                if (off < GRU_SIZE)
                        break;
                kgts = NULL;
        }
        BUG_ON(!kgts);
        cbrnum = thread_cbr_number(kgts, get_cb_number(cb));
        cbe = get_cbe(GRUBASE(cb), cbrnum);
        gru_flush_cache(cbe);   /* CBE not coherent */
        sync_core();
        excdet->opc = cbe->opccpy;
        excdet->exopc = cbe->exopccpy;
        excdet->ecause = cbe->ecause;
        excdet->exceptdet0 = cbe->idef1upd;
        excdet->exceptdet1 = cbe->idef3upd;
        gru_flush_cache(cbe);
        return 0;
}

static char *gru_get_cb_exception_detail_str(int ret, void *cb,
                                             char *buf, int size)
{
        struct gru_control_block_status *gen = cb;
        struct control_block_extended_exc_detail excdet;

        if (ret > 0 && gen->istatus == CBS_EXCEPTION) {
                gru_get_cb_exception_detail(cb, &excdet);
                snprintf(buf, size,
                        "GRU:%d exception: cb %p, opc %d, exopc %d, ecause 0x%x,"
                        "excdet0 0x%lx, excdet1 0x%x", smp_processor_id(),
                        gen, excdet.opc, excdet.exopc, excdet.ecause,
                        excdet.exceptdet0, excdet.exceptdet1);
        } else {
                snprintf(buf, size, "No exception");
        }
        return buf;
}

static int gru_wait_idle_or_exception(struct gru_control_block_status *gen)
{
        while (gen->istatus >= CBS_ACTIVE) {
                cpu_relax();
                barrier();
        }
        return gen->istatus;
}

static int gru_retry_exception(void *cb)
{
        struct gru_control_block_status *gen = cb;
        struct control_block_extended_exc_detail excdet;
        int retry = EXCEPTION_RETRY_LIMIT;

        while (1)  {
                if (gru_wait_idle_or_exception(gen) == CBS_IDLE)
                        return CBS_IDLE;
                if (gru_get_cb_message_queue_substatus(cb))
                        return CBS_EXCEPTION;
                gru_get_cb_exception_detail(cb, &excdet);
                if ((excdet.ecause & ~EXCEPTION_RETRY_BITS) ||
                                (excdet.cbrexecstatus & CBR_EXS_ABORT_OCC))
                        break;
                if (retry-- == 0)
                        break;
                gen->icmd = 1;
                gru_flush_cache(gen);
        }
        return CBS_EXCEPTION;
}

int gru_check_status_proc(void *cb)
{
        struct gru_control_block_status *gen = cb;
        int ret;

        ret = gen->istatus;
        if (ret == CBS_EXCEPTION)
                ret = gru_retry_exception(cb);
        rmb();
        return ret;

}

int gru_wait_proc(void *cb)
{
        struct gru_control_block_status *gen = cb;
        int ret;

        ret = gru_wait_idle_or_exception(gen);
        if (ret == CBS_EXCEPTION)
                ret = gru_retry_exception(cb);
        rmb();
        return ret;
}

static void gru_abort(int ret, void *cb, char *str)
{
        char buf[GRU_EXC_STR_SIZE];

        panic("GRU FATAL ERROR: %s - %s\n", str,
              gru_get_cb_exception_detail_str(ret, cb, buf, sizeof(buf)));
}

void gru_wait_abort_proc(void *cb)
{
        int ret;

        ret = gru_wait_proc(cb);
        if (ret)
                gru_abort(ret, cb, "gru_wait_abort");
}


/*------------------------------ MESSAGE QUEUES -----------------------------*/

/* Internal status . These are NOT returned to the user. */
#define MQIE_AGAIN              -1      /* try again */


/*
 * Save/restore the "present" flag that is in the second line of 2-line
 * messages
 */
static inline int get_present2(void *p)
{
        struct message_header *mhdr = p + GRU_CACHE_LINE_BYTES;
        return mhdr->present;
}

static inline void restore_present2(void *p, int val)
{
        struct message_header *mhdr = p + GRU_CACHE_LINE_BYTES;
        mhdr->present = val;
}

/*
 * Create a message queue.
 *      qlines - message queue size in cache lines. Includes 2-line header.
 */
int gru_create_message_queue(struct gru_message_queue_desc *mqd,
                void *p, unsigned int bytes, int nasid, int vector, int apicid)
{
        struct message_queue *mq = p;
        unsigned int qlines;

        qlines = bytes / GRU_CACHE_LINE_BYTES - 2;
        memset(mq, 0, bytes);
        mq->start = &mq->data;
        mq->start2 = &mq->data + (qlines / 2 - 1) * GRU_CACHE_LINE_BYTES;
        mq->next = &mq->data;
        mq->limit = &mq->data + (qlines - 2) * GRU_CACHE_LINE_BYTES;
        mq->qlines = qlines;
        mq->hstatus[0] = 0;
        mq->hstatus[1] = 1;
        mq->head = gru_mesq_head(2, qlines / 2 + 1);
        mqd->mq = mq;
        mqd->mq_gpa = uv_gpa(mq);
        mqd->qlines = qlines;
        mqd->interrupt_pnode = nasid >> 1;
        mqd->interrupt_vector = vector;
        mqd->interrupt_apicid = apicid;
        return 0;
}
EXPORT_SYMBOL_GPL(gru_create_message_queue);

/*
 * Send a NOOP message to a message queue
 *      Returns:
 *               0 - if queue is full after the send. This is the normal case
 *                   but various races can change this.
 *              -1 - if mesq sent successfully but queue not full
 *              >0 - unexpected error. MQE_xxx returned
 */
static int send_noop_message(void *cb, struct gru_message_queue_desc *mqd,
                                void *mesg)
{
        const struct message_header noop_header = {
                                        .present = MQS_NOOP, .lines = 1};
        unsigned long m;
        int substatus, ret;
        struct message_header save_mhdr, *mhdr = mesg;

        STAT(mesq_noop);
        save_mhdr = *mhdr;
        *mhdr = noop_header;
        gru_mesq(cb, mqd->mq_gpa, gru_get_tri(mhdr), 1, IMA);
        ret = gru_wait(cb);

        if (ret) {
                substatus = gru_get_cb_message_queue_substatus(cb);
                switch (substatus) {
                case CBSS_NO_ERROR:
                        STAT(mesq_noop_unexpected_error);
                        ret = MQE_UNEXPECTED_CB_ERR;
                        break;
                case CBSS_LB_OVERFLOWED:
                        STAT(mesq_noop_lb_overflow);
                        ret = MQE_CONGESTION;
                        break;
                case CBSS_QLIMIT_REACHED:
                        STAT(mesq_noop_qlimit_reached);
                        ret = 0;
                        break;
                case CBSS_AMO_NACKED:
                        STAT(mesq_noop_amo_nacked);
                        ret = MQE_CONGESTION;
                        break;
                case CBSS_PUT_NACKED:
                        STAT(mesq_noop_put_nacked);
                        m = mqd->mq_gpa + (gru_get_amo_value_head(cb) << 6);
                        gru_vstore(cb, m, gru_get_tri(mesg), XTYPE_CL, 1, 1,
                                                IMA);
                        if (gru_wait(cb) == CBS_IDLE)
                                ret = MQIE_AGAIN;
                        else
                                ret = MQE_UNEXPECTED_CB_ERR;
                        break;
                case CBSS_PAGE_OVERFLOW:
                        STAT(mesq_noop_page_overflow);
                        fallthrough;
                default:
                        BUG();
                }
        }
        *mhdr = save_mhdr;
        return ret;
}

/*
 * Handle a gru_mesq full.
 */
static int send_message_queue_full(void *cb, struct gru_message_queue_desc *mqd,
                                void *mesg, int lines)
{
        union gru_mesqhead mqh;
        unsigned int limit, head;
        unsigned long avalue;
        int half, qlines;

        /* Determine if switching to first/second half of q */
        avalue = gru_get_amo_value(cb);
        head = gru_get_amo_value_head(cb);
        limit = gru_get_amo_value_limit(cb);

        qlines = mqd->qlines;
        half = (limit != qlines);

        if (half)
                mqh = gru_mesq_head(qlines / 2 + 1, qlines);
        else
                mqh = gru_mesq_head(2, qlines / 2 + 1);

        /* Try to get lock for switching head pointer */
        gru_gamir(cb, EOP_IR_CLR, HSTATUS(mqd->mq_gpa, half), XTYPE_DW, IMA);
        if (gru_wait(cb) != CBS_IDLE)
                goto cberr;
        if (!gru_get_amo_value(cb)) {
                STAT(mesq_qf_locked);
                return MQE_QUEUE_FULL;
        }

        /* Got the lock. Send optional NOP if queue not full, */
        if (head != limit) {
                if (send_noop_message(cb, mqd, mesg)) {
                        gru_gamir(cb, EOP_IR_INC, HSTATUS(mqd->mq_gpa, half),
                                        XTYPE_DW, IMA);
                        if (gru_wait(cb) != CBS_IDLE)
                                goto cberr;
                        STAT(mesq_qf_noop_not_full);
                        return MQIE_AGAIN;
                }
                avalue++;
        }

        /* Then flip queuehead to other half of queue. */
        gru_gamer(cb, EOP_ERR_CSWAP, mqd->mq_gpa, XTYPE_DW, mqh.val, avalue,
                                                        IMA);
        if (gru_wait(cb) != CBS_IDLE)
                goto cberr;

        /* If not successfully in swapping queue head, clear the hstatus lock */
        if (gru_get_amo_value(cb) != avalue) {
                STAT(mesq_qf_switch_head_failed);
                gru_gamir(cb, EOP_IR_INC, HSTATUS(mqd->mq_gpa, half), XTYPE_DW,
                                                        IMA);
                if (gru_wait(cb) != CBS_IDLE)
                        goto cberr;
        }
        return MQIE_AGAIN;
cberr:
        STAT(mesq_qf_unexpected_error);
        return MQE_UNEXPECTED_CB_ERR;
}

/*
 * Handle a PUT failure. Note: if message was a 2-line message, one of the
 * lines might have successfully have been written. Before sending the
 * message, "present" must be cleared in BOTH lines to prevent the receiver
 * from prematurely seeing the full message.
 */
static int send_message_put_nacked(void *cb, struct gru_message_queue_desc *mqd,
                        void *mesg, int lines)
{
        unsigned long m;
        int ret, loops = 200;   /* experimentally determined */

        m = mqd->mq_gpa + (gru_get_amo_value_head(cb) << 6);
        if (lines == 2) {
                gru_vset(cb, m, 0, XTYPE_CL, lines, 1, IMA);
                if (gru_wait(cb) != CBS_IDLE)
                        return MQE_UNEXPECTED_CB_ERR;
        }
        gru_vstore(cb, m, gru_get_tri(mesg), XTYPE_CL, lines, 1, IMA);
        if (gru_wait(cb) != CBS_IDLE)
                return MQE_UNEXPECTED_CB_ERR;

        if (!mqd->interrupt_vector)
                return MQE_OK;

        /*
         * Send a noop message in order to deliver a cross-partition interrupt
         * to the SSI that contains the target message queue. Normally, the
         * interrupt is automatically delivered by hardware following mesq
         * operations, but some error conditions require explicit delivery.
         * The noop message will trigger delivery. Otherwise partition failures
         * could cause unrecovered errors.
         */
        do {
                ret = send_noop_message(cb, mqd, mesg);
        } while ((ret == MQIE_AGAIN || ret == MQE_CONGESTION) && (loops-- > 0));

        if (ret == MQIE_AGAIN || ret == MQE_CONGESTION) {
                /*
                 * Don't indicate to the app to resend the message, as it's
                 * already been successfully sent.  We simply send an OK
                 * (rather than fail the send with MQE_UNEXPECTED_CB_ERR),
                 * assuming that the other side is receiving enough
                 * interrupts to get this message processed anyway.
                 */
                ret = MQE_OK;
        }
        return ret;
}

/*
 * Handle a gru_mesq failure. Some of these failures are software recoverable
 * or retryable.
 */
static int send_message_failure(void *cb, struct gru_message_queue_desc *mqd,
                                void *mesg, int lines)
{
        int substatus, ret = 0;

        substatus = gru_get_cb_message_queue_substatus(cb);
        switch (substatus) {
        case CBSS_NO_ERROR:
                STAT(mesq_send_unexpected_error);
                ret = MQE_UNEXPECTED_CB_ERR;
                break;
        case CBSS_LB_OVERFLOWED:
                STAT(mesq_send_lb_overflow);
                ret = MQE_CONGESTION;
                break;
        case CBSS_QLIMIT_REACHED:
                STAT(mesq_send_qlimit_reached);
                ret = send_message_queue_full(cb, mqd, mesg, lines);
                break;
        case CBSS_AMO_NACKED:
                STAT(mesq_send_amo_nacked);
                ret = MQE_CONGESTION;
                break;
        case CBSS_PUT_NACKED:
                STAT(mesq_send_put_nacked);
                ret = send_message_put_nacked(cb, mqd, mesg, lines);
                break;
        case CBSS_PAGE_OVERFLOW:
                STAT(mesq_page_overflow);
                fallthrough;
        default:
                BUG();
        }
        return ret;
}

/*
 * Send a message to a message queue
 *      mqd     message queue descriptor
 *      mesg    message. ust be vaddr within a GSEG
 *      bytes   message size (<= 2 CL)
 */
int gru_send_message_gpa(struct gru_message_queue_desc *mqd, void *mesg,
                                unsigned int bytes)
{
        struct message_header *mhdr;
        void *cb;
        void *dsr;
        int istatus, clines, ret;

        STAT(mesq_send);
        BUG_ON(bytes < sizeof(int) || bytes > 2 * GRU_CACHE_LINE_BYTES);

        clines = DIV_ROUND_UP(bytes, GRU_CACHE_LINE_BYTES);
        if (gru_get_cpu_resources(bytes, &cb, &dsr))
                return MQE_BUG_NO_RESOURCES;
        memcpy(dsr, mesg, bytes);
        mhdr = dsr;
        mhdr->present = MQS_FULL;
        mhdr->lines = clines;
        if (clines == 2) {
                mhdr->present2 = get_present2(mhdr);
                restore_present2(mhdr, MQS_FULL);
        }

        do {
                ret = MQE_OK;
                gru_mesq(cb, mqd->mq_gpa, gru_get_tri(mhdr), clines, IMA);
                istatus = gru_wait(cb);
                if (istatus != CBS_IDLE)
                        ret = send_message_failure(cb, mqd, dsr, clines);
        } while (ret == MQIE_AGAIN);
        gru_free_cpu_resources(cb, dsr);

        if (ret)
                STAT(mesq_send_failed);
        return ret;
}
EXPORT_SYMBOL_GPL(gru_send_message_gpa);

/*
 * Advance the receive pointer for the queue to the next message.
 */
void gru_free_message(struct gru_message_queue_desc *mqd, void *mesg)
{
        struct message_queue *mq = mqd->mq;
        struct message_header *mhdr = mq->next;
        void *next, *pnext;
        int half = -1;
        int lines = mhdr->lines;

        if (lines == 2)
                restore_present2(mhdr, MQS_EMPTY);
        mhdr->present = MQS_EMPTY;

        pnext = mq->next;
        next = pnext + GRU_CACHE_LINE_BYTES * lines;
        if (next == mq->limit) {
                next = mq->start;
                half = 1;
        } else if (pnext < mq->start2 && next >= mq->start2) {
                half = 0;
        }

        if (half >= 0)
                mq->hstatus[half] = 1;
        mq->next = next;
}
EXPORT_SYMBOL_GPL(gru_free_message);

/*
 * Get next message from message queue. Return NULL if no message
 * present. User must call next_message() to move to next message.
 *      rmq     message queue
 */
void *gru_get_next_message(struct gru_message_queue_desc *mqd)
{
        struct message_queue *mq = mqd->mq;
        struct message_header *mhdr = mq->next;
        int present = mhdr->present;

        /* skip NOOP messages */
        while (present == MQS_NOOP) {
                gru_free_message(mqd, mhdr);
                mhdr = mq->next;
                present = mhdr->present;
        }

        /* Wait for both halves of 2 line messages */
        if (present == MQS_FULL && mhdr->lines == 2 &&
                                get_present2(mhdr) == MQS_EMPTY)
                present = MQS_EMPTY;

        if (!present) {
                STAT(mesq_receive_none);
                return NULL;
        }

        if (mhdr->lines == 2)
                restore_present2(mhdr, mhdr->present2);

        STAT(mesq_receive);
        return mhdr;
}
EXPORT_SYMBOL_GPL(gru_get_next_message);

/* ---------------------- GRU DATA COPY FUNCTIONS ---------------------------*/

/*
 * Load a DW from a global GPA. The GPA can be a memory or MMR address.
 */
int gru_read_gpa(unsigned long *value, unsigned long gpa)
{
        void *cb;
        void *dsr;
        int ret, iaa;

        STAT(read_gpa);
        if (gru_get_cpu_resources(GRU_NUM_KERNEL_DSR_BYTES, &cb, &dsr))
                return MQE_BUG_NO_RESOURCES;
        iaa = gpa >> 62;
        gru_vload_phys(cb, gpa, gru_get_tri(dsr), iaa, IMA);
        ret = gru_wait(cb);
        if (ret == CBS_IDLE)
                *value = *(unsigned long *)dsr;
        gru_free_cpu_resources(cb, dsr);
        return ret;
}
EXPORT_SYMBOL_GPL(gru_read_gpa);


/*
 * Copy a block of data using the GRU resources
 */
int gru_copy_gpa(unsigned long dest_gpa, unsigned long src_gpa,
                                unsigned int bytes)
{
        void *cb;
        void *dsr;
        int ret;

        STAT(copy_gpa);
        if (gru_get_cpu_resources(GRU_NUM_KERNEL_DSR_BYTES, &cb, &dsr))
                return MQE_BUG_NO_RESOURCES;
        gru_bcopy(cb, src_gpa, dest_gpa, gru_get_tri(dsr),
                  XTYPE_B, bytes, GRU_NUM_KERNEL_DSR_CL, IMA);
        ret = gru_wait(cb);
        gru_free_cpu_resources(cb, dsr);
        return ret;
}
EXPORT_SYMBOL_GPL(gru_copy_gpa);

/* ------------------- KERNEL QUICKTESTS RUN AT STARTUP ----------------*/
/*      Temp - will delete after we gain confidence in the GRU          */

static int quicktest0(unsigned long arg)
{
        unsigned long word0;
        unsigned long word1;
        void *cb;
        void *dsr;
        unsigned long *p;
        int ret = -EIO;

        if (gru_get_cpu_resources(GRU_CACHE_LINE_BYTES, &cb, &dsr))
                return MQE_BUG_NO_RESOURCES;
        p = dsr;
        word0 = MAGIC;
        word1 = 0;

        gru_vload(cb, uv_gpa(&word0), gru_get_tri(dsr), XTYPE_DW, 1, 1, IMA);
        if (gru_wait(cb) != CBS_IDLE) {
                printk(KERN_DEBUG "GRU:%d quicktest0: CBR failure 1\n", smp_processor_id());
                goto done;
        }

        if (*p != MAGIC) {
                printk(KERN_DEBUG "GRU:%d quicktest0 bad magic 0x%lx\n", smp_processor_id(), *p);
                goto done;
        }
        gru_vstore(cb, uv_gpa(&word1), gru_get_tri(dsr), XTYPE_DW, 1, 1, IMA);
        if (gru_wait(cb) != CBS_IDLE) {
                printk(KERN_DEBUG "GRU:%d quicktest0: CBR failure 2\n", smp_processor_id());
                goto done;
        }

        if (word0 != word1 || word1 != MAGIC) {
                printk(KERN_DEBUG
                       "GRU:%d quicktest0 err: found 0x%lx, expected 0x%lx\n",
                     smp_processor_id(), word1, MAGIC);
                goto done;
        }
        ret = 0;

done:
        gru_free_cpu_resources(cb, dsr);
        return ret;
}

#define ALIGNUP(p, q)   ((void *)(((unsigned long)(p) + (q) - 1) & ~(q - 1)))

static int quicktest1(unsigned long arg)
{
        struct gru_message_queue_desc mqd;
        void *p, *mq;
        int i, ret = -EIO;
        char mes[GRU_CACHE_LINE_BYTES], *m;

        /* Need  1K cacheline aligned that does not cross page boundary */
        p = kmalloc(4096, 0);
        if (p == NULL)
                return -ENOMEM;
        mq = ALIGNUP(p, 1024);
        memset(mes, 0xee, sizeof(mes));

        gru_create_message_queue(&mqd, mq, 8 * GRU_CACHE_LINE_BYTES, 0, 0, 0);
        for (i = 0; i < 6; i++) {
                mes[8] = i;
                do {
                        ret = gru_send_message_gpa(&mqd, mes, sizeof(mes));
                } while (ret == MQE_CONGESTION);
                if (ret)
                        break;
        }
        if (ret != MQE_QUEUE_FULL || i != 4) {
                printk(KERN_DEBUG "GRU:%d quicktest1: unexpected status %d, i %d\n",
                       smp_processor_id(), ret, i);
                goto done;
        }

        for (i = 0; i < 6; i++) {
                m = gru_get_next_message(&mqd);
                if (!m || m[8] != i)
                        break;
                gru_free_message(&mqd, m);
        }
        if (i != 4) {
                printk(KERN_DEBUG "GRU:%d quicktest2: bad message, i %d, m %p, m8 %d\n",
                        smp_processor_id(), i, m, m ? m[8] : -1);
                goto done;
        }
        ret = 0;

done:
        kfree(p);
        return ret;
}

static int quicktest2(unsigned long arg)
{
        static DECLARE_COMPLETION(cmp);
        unsigned long han;
        int blade_id = 0;
        int numcb = 4;
        int ret = 0;
        unsigned long *buf;
        void *cb0, *cb;
        struct gru_control_block_status *gen;
        int i, k, istatus, bytes;

        bytes = numcb * 4 * 8;
        buf = kmalloc(bytes, GFP_KERNEL);
        if (!buf)
                return -ENOMEM;

        ret = -EBUSY;
        han = gru_reserve_async_resources(blade_id, numcb, 0, &cmp);
        if (!han)
                goto done;

        gru_lock_async_resource(han, &cb0, NULL);
        memset(buf, 0xee, bytes);
        for (i = 0; i < numcb; i++)
                gru_vset(cb0 + i * GRU_HANDLE_STRIDE, uv_gpa(&buf[i * 4]), 0,
                                XTYPE_DW, 4, 1, IMA_INTERRUPT);

        ret = 0;
        k = numcb;
        do {
                gru_wait_async_cbr(han);
                for (i = 0; i < numcb; i++) {
                        cb = cb0 + i * GRU_HANDLE_STRIDE;
                        istatus = gru_check_status(cb);
                        if (istatus != CBS_ACTIVE && istatus != CBS_CALL_OS)
                                break;
                }
                if (i == numcb)
                        continue;
                if (istatus != CBS_IDLE) {
                        printk(KERN_DEBUG "GRU:%d quicktest2: cb %d, exception\n", smp_processor_id(), i);
                        ret = -EFAULT;
                } else if (buf[4 * i] || buf[4 * i + 1] || buf[4 * i + 2] ||
                                buf[4 * i + 3]) {
                        printk(KERN_DEBUG "GRU:%d quicktest2:cb %d,  buf 0x%lx, 0x%lx, 0x%lx, 0x%lx\n",
                               smp_processor_id(), i, buf[4 * i], buf[4 * i + 1], buf[4 * i + 2], buf[4 * i + 3]);
                        ret = -EIO;
                }
                k--;
                gen = cb;
                gen->istatus = CBS_CALL_OS; /* don't handle this CBR again */
        } while (k);
        BUG_ON(cmp.done);

        gru_unlock_async_resource(han);
        gru_release_async_resources(han);
done:
        kfree(buf);
        return ret;
}

#define BUFSIZE 200
static int quicktest3(unsigned long arg)
{
        char buf1[BUFSIZE], buf2[BUFSIZE];
        int ret = 0;

        memset(buf2, 0, sizeof(buf2));
        memset(buf1, get_cycles() & 255, sizeof(buf1));
        gru_copy_gpa(uv_gpa(buf2), uv_gpa(buf1), BUFSIZE);
        if (memcmp(buf1, buf2, BUFSIZE)) {
                printk(KERN_DEBUG "GRU:%d quicktest3 error\n", smp_processor_id());
                ret = -EIO;
        }
        return ret;
}

/*
 * Debugging only. User hook for various kernel tests
 * of driver & gru.
 */
int gru_ktest(unsigned long arg)
{
        int ret = -EINVAL;

        switch (arg & 0xff) {
        case 0:
                ret = quicktest0(arg);
                break;
        case 1:
                ret = quicktest1(arg);
                break;
        case 2:
                ret = quicktest2(arg);
                break;
        case 3:
                ret = quicktest3(arg);
                break;
        case 99:
                ret = gru_free_kernel_contexts();
                break;
        }
        return ret;

}

int gru_kservices_init(void)
{
        return 0;
}

void gru_kservices_exit(void)
{
        if (gru_free_kernel_contexts())
                BUG();
}