drivers/misc/sgi-gru/grufault.c

   1 /*
   2  * SN Platform GRU Driver
   3  *
   4  *              FAULT HANDLER FOR GRU DETECTED TLB MISSES
   5  *
   6  * This file contains code that handles TLB misses within the GRU.
   7  * These misses are reported either via interrupts or user polling of
   8  * the user CB.
   9  *
  10  *  Copyright (c) 2008 Silicon Graphics, Inc.  All Rights Reserved.
  11  *
  12  *  This program is free software; you can redistribute it and/or modify
  13  *  it under the terms of the GNU General Public License as published by
  14  *  the Free Software Foundation; either version 2 of the License, or
  15  *  (at your option) any later version.
  16  *
  17  *  This program is distributed in the hope that it will be useful,
  18  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  19  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  20  *  GNU General Public License for more details.
  21  *
  22  *  You should have received a copy of the GNU General Public License
  23  *  along with this program; if not, write to the Free Software
  24  *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
  25  */
  26
  27 #include <linux/kernel.h>
  28 #include <linux/errno.h>
  29 #include <linux/spinlock.h>
  30 #include <linux/mm.h>
  31 #include <linux/hugetlb.h>
  32 #include <linux/device.h>
  33 #include <linux/io.h>
  34 #include <linux/uaccess.h>
  35 #include <asm/pgtable.h>
  36 #include "gru.h"
  37 #include "grutables.h"
  38 #include "grulib.h"
  39 #include "gru_instructions.h"
  40 #include <asm/uv/uv_hub.h>
  41
  42 /*
  43  * Test if a physical address is a valid GRU GSEG address
  44  */
  45 static inline int is_gru_paddr(unsigned long paddr)
  46 {
  47         return paddr >= gru_start_paddr && paddr < gru_end_paddr;
  48 }
  49
  50 /*
  51  * Find the vma of a GRU segment. Caller must hold mmap_sem.
  52  */
  53 struct vm_area_struct *gru_find_vma(unsigned long vaddr)
  54 {
  55         struct vm_area_struct *vma;
  56
  57         vma = find_vma(current->mm, vaddr);
  58         if (vma && vma->vm_start <= vaddr && vma->vm_ops == &gru_vm_ops)
  59                 return vma;
  60         return NULL;
  61 }
  62
  63 /*
  64  * Find and lock the gts that contains the specified user vaddr.
  65  *
  66  * Returns:
  67  *      - *gts with the mmap_sem locked for read and the GTS locked.
  68  *      - NULL if vaddr invalid OR is not a valid GSEG vaddr.
  69  */
  70
  71 static struct gru_thread_state *gru_find_lock_gts(unsigned long vaddr)
  72 {
  73         struct mm_struct *mm = current->mm;
  74         struct vm_area_struct *vma;
  75         struct gru_thread_state *gts = NULL;
  76
  77         down_read(&mm->mmap_sem);
  78         vma = gru_find_vma(vaddr);
  79         if (vma)
  80                 gts = gru_find_thread_state(vma, TSID(vaddr, vma));
  81         if (gts)
  82                 mutex_lock(&gts->ts_ctxlock);
  83         else
  84                 up_read(&mm->mmap_sem);
  85         return gts;
  86 }
  87
  88 static struct gru_thread_state *gru_alloc_locked_gts(unsigned long vaddr)
  89 {
  90         struct mm_struct *mm = current->mm;
  91         struct vm_area_struct *vma;
  92         struct gru_thread_state *gts = NULL;
  93
  94         down_write(&mm->mmap_sem);
  95         vma = gru_find_vma(vaddr);
  96         if (vma)
  97                 gts = gru_alloc_thread_state(vma, TSID(vaddr, vma));
  98         if (gts) {
  99                 mutex_lock(&gts->ts_ctxlock);
 100                 downgrade_write(&mm->mmap_sem);
 101         } else {
 102                 up_write(&mm->mmap_sem);
 103         }
 104
 105         return gts;
 106 }
 107
 108 /*
 109  * Unlock a GTS that was previously locked with gru_find_lock_gts().
 110  */
 111 static void gru_unlock_gts(struct gru_thread_state *gts)
 112 {
 113         mutex_unlock(&gts->ts_ctxlock);
 114         up_read(&current->mm->mmap_sem);
 115 }
 116
 117 /*
 118  * Set a CB.istatus to active using a user virtual address. This must be done
 119  * just prior to a TFH RESTART. The new cb.istatus is an in-cache status ONLY.
 120  * If the line is evicted, the status may be lost. The in-cache update
 121  * is necessary to prevent the user from seeing a stale cb.istatus that will
 122  * change as soon as the TFH restart is complete. Races may cause an
 123  * occasional failure to clear the cb.istatus, but that is ok.
 124  *
 125  * If the cb address is not valid (should not happen, but...), nothing
 126  * bad will happen.. The get_user()/put_user() will fail but there
 127  * are no bad side-effects.
 128  */
 129 static void gru_cb_set_istatus_active(unsigned long __user *cb)
 130 {
 131         union {
 132                 struct gru_instruction_bits bits;
 133                 unsigned long dw;
 134         } u;
 135
 136         if (cb) {
 137                 get_user(u.dw, cb);
 138                 u.bits.istatus = CBS_ACTIVE;
 139                 put_user(u.dw, cb);
 140         }
 141 }
 142
 143 /*
 144  * Convert a interrupt IRQ to a pointer to the GRU GTS that caused the
 145  * interrupt. Interrupts are always sent to a cpu on the blade that contains the
 146  * GRU (except for headless blades which are not currently supported). A blade
 147  * has N grus; a block of N consecutive IRQs is assigned to the GRUs. The IRQ
 148  * number uniquely identifies the GRU chiplet on the local blade that caused the
 149  * interrupt. Always called in interrupt context.
 150  */
 151 static inline struct gru_state *irq_to_gru(int irq)
 152 {
 153         return &gru_base[uv_numa_blade_id()]->bs_grus[irq - IRQ_GRU];
 154 }
 155
 156 /*
 157  * Read & clear a TFM
 158  *
 159  * The GRU has an array of fault maps. A map is private to a cpu
 160  * Only one cpu will be accessing a cpu's fault map.
 161  *
 162  * This function scans the cpu-private fault map & clears all bits that
 163  * are set. The function returns a bitmap that indicates the bits that
 164  * were cleared. Note that sense the maps may be updated asynchronously by
 165  * the GRU, atomic operations must be used to clear bits.
 166  */
 167 static void get_clear_fault_map(struct gru_state *gru,
 168                                 struct gru_tlb_fault_map *map)
 169 {
 170         unsigned long i, k;
 171         struct gru_tlb_fault_map *tfm;
 172
 173         tfm = get_tfm_for_cpu(gru, gru_cpu_fault_map_id());
 174         prefetchw(tfm);         /* Helps on hardware, required for emulator */
 175         for (i = 0; i < BITS_TO_LONGS(GRU_NUM_CBE); i++) {
 176                 k = tfm->fault_bits[i];
 177                 if (k)
 178                         k = xchg(&tfm->fault_bits[i], 0UL);
 179                 map->fault_bits[i] = k;
 180         }
 181
 182         /*
 183          * Not functionally required but helps performance. (Required
 184          * on emulator)
 185          */
 186         gru_flush_cache(tfm);
 187 }
 188
 189 /*
 190  * Atomic (interrupt context) & non-atomic (user context) functions to
 191  * convert a vaddr into a physical address. The size of the page
 192  * is returned in pageshift.
 193  *      returns:
 194  *                0 - successful
 195  *              < 0 - error code
 196  *                1 - (atomic only) try again in non-atomic context
 197  */
 198 static int non_atomic_pte_lookup(struct vm_area_struct *vma,
 199                                  unsigned long vaddr, int write,
 200                                  unsigned long *paddr, int *pageshift)
 201 {
 202         struct page *page;
 203
 204         /* ZZZ Need to handle HUGE pages */
 205         if (is_vm_hugetlb_page(vma))
 206                 return -EFAULT;
 207         *pageshift = PAGE_SHIFT;
 208         if (get_user_pages
 209             (current, current->mm, vaddr, 1, write, 0, &page, NULL) <= 0)
 210                 return -EFAULT;
 211         *paddr = page_to_phys(page);
 212         put_page(page);
 213         return 0;
 214 }
 215
 216 /*
 217  * atomic_pte_lookup
 218  *
 219  * Convert a user virtual address to a physical address
 220  * Only supports Intel large pages (2MB only) on x86_64.
 221  *      ZZZ - hugepage support is incomplete
 222  *
 223  * NOTE: mmap_sem is already held on entry to this function. This
 224  * guarantees existence of the page tables.
 225  */
 226 static int atomic_pte_lookup(struct vm_area_struct *vma, unsigned long vaddr,
 227         int write, unsigned long *paddr, int *pageshift)
 228 {
 229         pgd_t *pgdp;
 230         pmd_t *pmdp;
 231         pud_t *pudp;
 232         pte_t pte;
 233
 234         pgdp = pgd_offset(vma->vm_mm, vaddr);
 235         if (unlikely(pgd_none(*pgdp)))
 236                 goto err;
 237
 238         pudp = pud_offset(pgdp, vaddr);
 239         if (unlikely(pud_none(*pudp)))
 240                 goto err;
 241
 242         pmdp = pmd_offset(pudp, vaddr);
 243         if (unlikely(pmd_none(*pmdp)))
 244                 goto err;
 245 #ifdef CONFIG_X86_64
 246         if (unlikely(pmd_large(*pmdp)))
 247                 pte = *(pte_t *) pmdp;
 248         else
 249 #endif
 250                 pte = *pte_offset_kernel(pmdp, vaddr);
 251
 252         if (unlikely(!pte_present(pte) ||
 253                      (write && (!pte_write(pte) || !pte_dirty(pte)))))
 254                 return 1;
 255
 256         *paddr = pte_pfn(pte) << PAGE_SHIFT;
 257 #ifdef CONFIG_HUGETLB_PAGE
 258         *pageshift = is_vm_hugetlb_page(vma) ? HPAGE_SHIFT : PAGE_SHIFT;
 259 #else
 260         *pageshift = PAGE_SHIFT;
 261 #endif
 262         return 0;
 263
 264 err:
 265         local_irq_enable();
 266         return 1;
 267 }
 268
 269 /*
 270  * Drop a TLB entry into the GRU. The fault is described by info in an TFH.
 271  *      Input:
 272  *              cb    Address of user CBR. Null if not running in user context
 273  *      Return:
 274  *                0 = dropin, exception, or switch to UPM successful
 275  *                1 = range invalidate active
 276  *              < 0 = error code
 277  *
 278  */
 279 static int gru_try_dropin(struct gru_thread_state *gts,
 280                           struct gru_tlb_fault_handle *tfh,
 281                           unsigned long __user *cb)
 282 {
 283         struct mm_struct *mm = gts->ts_mm;
 284         struct vm_area_struct *vma;
 285         int pageshift, asid, write, ret;
 286         unsigned long paddr, gpa, vaddr;
 287
 288         /*
 289          * NOTE: The GRU contains magic hardware that eliminates races between
 290          * TLB invalidates and TLB dropins. If an invalidate occurs
 291          * in the window between reading the TFH and the subsequent TLB dropin,
 292          * the dropin is ignored. This eliminates the need for additional locks.
 293          */
 294
 295         /*
 296          * Error if TFH state is IDLE or FMM mode & the user issuing a UPM call.
 297          * Might be a hardware race OR a stupid user. Ignore FMM because FMM
 298          * is a transient state.
 299          */
 300         if (tfh->state == TFHSTATE_IDLE)
 301                 goto failidle;
 302         if (tfh->state == TFHSTATE_MISS_FMM && cb)
 303                 goto failfmm;
 304
 305         write = (tfh->cause & TFHCAUSE_TLB_MOD) != 0;
 306         vaddr = tfh->missvaddr;
 307         asid = tfh->missasid;
 308         if (asid == 0)
 309                 goto failnoasid;
 310
 311         rmb();  /* TFH must be cache resident before reading ms_range_active */
 312
 313         /*
 314          * TFH is cache resident - at least briefly. Fail the dropin
 315          * if a range invalidate is active.
 316          */
 317         if (atomic_read(&gts->ts_gms->ms_range_active))
 318                 goto failactive;
 319
 320         vma = find_vma(mm, vaddr);
 321         if (!vma)
 322                 goto failinval;
 323
 324         /*
 325          * Atomic lookup is faster & usually works even if called in non-atomic
 326          * context.
 327          */
 328         rmb();  /* Must/check ms_range_active before loading PTEs */
 329         ret = atomic_pte_lookup(vma, vaddr, write, &paddr, &pageshift);
 330         if (ret) {
 331                 if (!cb)
 332                         goto failupm;
 333                 if (non_atomic_pte_lookup(vma, vaddr, write, &paddr,
 334                                           &pageshift))
 335                         goto failinval;
 336         }
 337         if (is_gru_paddr(paddr))
 338                 goto failinval;
 339
 340         paddr = paddr & ~((1UL << pageshift) - 1);
 341         gpa = uv_soc_phys_ram_to_gpa(paddr);
 342         gru_cb_set_istatus_active(cb);
 343         tfh_write_restart(tfh, gpa, GAA_RAM, vaddr, asid, write,
 344                           GRU_PAGESIZE(pageshift));
 345         STAT(tlb_dropin);
 346         gru_dbg(grudev,
 347                 "%s: tfh 0x%p, vaddr 0x%lx, asid 0x%x, ps %d, gpa 0x%lx\n",
 348                 ret ? "non-atomic" : "atomic", tfh, vaddr, asid,
 349                 pageshift, gpa);
 350         return 0;
 351
 352 failnoasid:
 353         /* No asid (delayed unload). */
 354         STAT(tlb_dropin_fail_no_asid);
 355         gru_dbg(grudev, "FAILED no_asid tfh: 0x%p, vaddr 0x%lx\n", tfh, vaddr);
 356         if (!cb)
 357                 tfh_user_polling_mode(tfh);
 358         else
 359                 gru_flush_cache(tfh);
 360         return -EAGAIN;
 361
 362 failupm:
 363         /* Atomic failure switch CBR to UPM */
 364         tfh_user_polling_mode(tfh);
 365         STAT(tlb_dropin_fail_upm);
 366         gru_dbg(grudev, "FAILED upm tfh: 0x%p, vaddr 0x%lx\n", tfh, vaddr);
 367         return 1;
 368
 369 failfmm:
 370         /* FMM state on UPM call */
 371         STAT(tlb_dropin_fail_fmm);
 372         gru_dbg(grudev, "FAILED fmm tfh: 0x%p, state %d\n", tfh, tfh->state);
 373         return 0;
 374
 375 failidle:
 376         /* TFH was idle  - no miss pending */
 377         gru_flush_cache(tfh);
 378         if (cb)
 379                 gru_flush_cache(cb);
 380         STAT(tlb_dropin_fail_idle);
 381         gru_dbg(grudev, "FAILED idle tfh: 0x%p, state %d\n", tfh, tfh->state);
 382         return 0;
 383
 384 failinval:
 385         /* All errors (atomic & non-atomic) switch CBR to EXCEPTION state */
 386         tfh_exception(tfh);
 387         STAT(tlb_dropin_fail_invalid);
 388         gru_dbg(grudev, "FAILED inval tfh: 0x%p, vaddr 0x%lx\n", tfh, vaddr);
 389         return -EFAULT;
 390
 391 failactive:
 392         /* Range invalidate active. Switch to UPM iff atomic */
 393         if (!cb)
 394                 tfh_user_polling_mode(tfh);
 395         else
 396                 gru_flush_cache(tfh);
 397         STAT(tlb_dropin_fail_range_active);
 398         gru_dbg(grudev, "FAILED range active: tfh 0x%p, vaddr 0x%lx\n",
 399                 tfh, vaddr);
 400         return 1;
 401 }
 402
 403 /*
 404  * Process an external interrupt from the GRU. This interrupt is
 405  * caused by a TLB miss.
 406  * Note that this is the interrupt handler that is registered with linux
 407  * interrupt handlers.
 408  */
 409 irqreturn_t gru_intr(int irq, void *dev_id)
 410 {
 411         struct gru_state *gru;
 412         struct gru_tlb_fault_map map;
 413         struct gru_thread_state *gts;
 414         struct gru_tlb_fault_handle *tfh = NULL;
 415         int cbrnum, ctxnum;
 416
 417         STAT(intr);
 418
 419         gru = irq_to_gru(irq);
 420         if (!gru) {
 421                 dev_err(grudev, "GRU: invalid interrupt: cpu %d, irq %d\n",
 422                         raw_smp_processor_id(), irq);
 423                 return IRQ_NONE;
 424         }
 425         get_clear_fault_map(gru, &map);
 426         gru_dbg(grudev, "irq %d, gru %x, map 0x%lx\n", irq, gru->gs_gid,
 427                 map.fault_bits[0]);
 428
 429         for_each_cbr_in_tfm(cbrnum, map.fault_bits) {
 430                 tfh = get_tfh_by_index(gru, cbrnum);
 431                 prefetchw(tfh); /* Helps on hdw, required for emulator */
 432
 433                 /*
 434                  * When hardware sets a bit in the faultmap, it implicitly
 435                  * locks the GRU context so that it cannot be unloaded.
 436                  * The gts cannot change until a TFH start/writestart command
 437                  * is issued.
 438                  */
 439                 ctxnum = tfh->ctxnum;
 440                 gts = gru->gs_gts[ctxnum];
 441
 442                 /*
 443                  * This is running in interrupt context. Trylock the mmap_sem.
 444                  * If it fails, retry the fault in user context.
 445                  */
 446                 if (down_read_trylock(&gts->ts_mm->mmap_sem)) {
 447                         gru_try_dropin(gts, tfh, NULL);
 448                         up_read(&gts->ts_mm->mmap_sem);
 449                 } else {
 450                         tfh_user_polling_mode(tfh);
 451                 }
 452         }
 453         return IRQ_HANDLED;
 454 }
 455
 456
 457 static int gru_user_dropin(struct gru_thread_state *gts,
 458                            struct gru_tlb_fault_handle *tfh,
 459                            unsigned long __user *cb)
 460 {
 461         struct gru_mm_struct *gms = gts->ts_gms;
 462         int ret;
 463
 464         while (1) {
 465                 wait_event(gms->ms_wait_queue,
 466                            atomic_read(&gms->ms_range_active) == 0);
 467                 prefetchw(tfh); /* Helps on hdw, required for emulator */
 468                 ret = gru_try_dropin(gts, tfh, cb);
 469                 if (ret <= 0)
 470                         return ret;
 471                 STAT(call_os_wait_queue);
 472         }
 473 }
 474
 475 /*
 476  * This interface is called as a result of a user detecting a "call OS" bit
 477  * in a user CB. Normally means that a TLB fault has occurred.
 478  *      cb - user virtual address of the CB
 479  */
 480 int gru_handle_user_call_os(unsigned long cb)
 481 {
 482         struct gru_tlb_fault_handle *tfh;
 483         struct gru_thread_state *gts;
 484         unsigned long __user *cbp;
 485         int ucbnum, cbrnum, ret = -EINVAL;
 486
 487         STAT(call_os);
 488         gru_dbg(grudev, "address 0x%lx\n", cb);
 489
 490         /* sanity check the cb pointer */
 491         ucbnum = get_cb_number((void *)cb);
 492         if ((cb & (GRU_HANDLE_STRIDE - 1)) || ucbnum >= GRU_NUM_CB)
 493                 return -EINVAL;
 494         cbp = (unsigned long *)cb;
 495
 496         gts = gru_find_lock_gts(cb);
 497         if (!gts)
 498                 return -EINVAL;
 499
 500         if (ucbnum >= gts->ts_cbr_au_count * GRU_CBR_AU_SIZE) {
 501                 ret = -EINVAL;
 502                 goto exit;
 503         }
 504
 505         /*
 506          * If force_unload is set, the UPM TLB fault is phony. The task
 507          * has migrated to another node and the GSEG must be moved. Just
 508          * unload the context. The task will page fault and assign a new
 509          * context.
 510          */
 511         ret = -EAGAIN;
 512         cbrnum = thread_cbr_number(gts, ucbnum);
 513         if (gts->ts_force_unload) {
 514                 gru_unload_context(gts, 1);
 515         } else if (gts->ts_gru) {
 516                 tfh = get_tfh_by_index(gts->ts_gru, cbrnum);
 517                 ret = gru_user_dropin(gts, tfh, cbp);
 518         }
 519 exit:
 520         gru_unlock_gts(gts);
 521         return ret;
 522 }
 523
 524 /*
 525  * Fetch the exception detail information for a CB that terminated with
 526  * an exception.
 527  */
 528 int gru_get_exception_detail(unsigned long arg)
 529 {
 530         struct control_block_extended_exc_detail excdet;
 531         struct gru_control_block_extended *cbe;
 532         struct gru_thread_state *gts;
 533         int ucbnum, cbrnum, ret;
 534
 535         STAT(user_exception);
 536         if (copy_from_user(&excdet, (void __user *)arg, sizeof(excdet)))
 537                 return -EFAULT;
 538
 539         gru_dbg(grudev, "address 0x%lx\n", excdet.cb);
 540         gts = gru_find_lock_gts(excdet.cb);
 541         if (!gts)
 542                 return -EINVAL;
 543
 544         if (gts->ts_gru) {
 545                 ucbnum = get_cb_number((void *)excdet.cb);
 546                 cbrnum = thread_cbr_number(gts, ucbnum);
 547                 cbe = get_cbe_by_index(gts->ts_gru, cbrnum);
 548                 prefetchw(cbe);         /* Harmless on hardware, required for emulator */
 549                 excdet.opc = cbe->opccpy;
 550                 excdet.exopc = cbe->exopccpy;
 551                 excdet.ecause = cbe->ecause;
 552                 excdet.exceptdet0 = cbe->idef1upd;
 553                 excdet.exceptdet1 = cbe->idef3upd;
 554                 ret = 0;
 555         } else {
 556                 ret = -EAGAIN;
 557         }
 558         gru_unlock_gts(gts);
 559
 560         gru_dbg(grudev, "address 0x%lx, ecause 0x%x\n", excdet.cb,
 561                 excdet.ecause);
 562         if (!ret && copy_to_user((void __user *)arg, &excdet, sizeof(excdet)))
 563                 ret = -EFAULT;
 564         return ret;
 565 }
 566
 567 /*
 568  * User request to unload a context. Content is saved for possible reload.
 569  */
 570 int gru_user_unload_context(unsigned long arg)
 571 {
 572         struct gru_thread_state *gts;
 573         struct gru_unload_context_req req;
 574
 575         STAT(user_unload_context);
 576         if (copy_from_user(&req, (void __user *)arg, sizeof(req)))
 577                 return -EFAULT;
 578
 579         gru_dbg(grudev, "gseg 0x%lx\n", req.gseg);
 580
 581         gts = gru_find_lock_gts(req.gseg);
 582         if (!gts)
 583                 return -EINVAL;
 584
 585         if (gts->ts_gru)
 586                 gru_unload_context(gts, 1);
 587         gru_unlock_gts(gts);
 588
 589         return 0;
 590 }
 591
 592 /*
 593  * User request to flush a range of virtual addresses from the GRU TLB
 594  * (Mainly for testing).
 595  */
 596 int gru_user_flush_tlb(unsigned long arg)
 597 {
 598         struct gru_thread_state *gts;
 599         struct gru_flush_tlb_req req;
 600
 601         STAT(user_flush_tlb);
 602         if (copy_from_user(&req, (void __user *)arg, sizeof(req)))
 603                 return -EFAULT;
 604
 605         gru_dbg(grudev, "gseg 0x%lx, vaddr 0x%lx, len 0x%lx\n", req.gseg,
 606                 req.vaddr, req.len);
 607
 608         gts = gru_find_lock_gts(req.gseg);
 609         if (!gts)
 610                 return -EINVAL;
 611
 612         gru_flush_tlb_range(gts->ts_gms, req.vaddr, req.vaddr + req.len);
 613         gru_unlock_gts(gts);
 614
 615         return 0;
 616 }
 617
 618 /*
 619  * Register the current task as the user of the GSEG slice.
 620  * Needed for TLB fault interrupt targeting.
 621  */
 622 int gru_set_task_slice(long address)
 623 {
 624         struct gru_thread_state *gts;
 625
 626         STAT(set_task_slice);
 627         gru_dbg(grudev, "address 0x%lx\n", address);
 628         gts = gru_alloc_locked_gts(address);
 629         if (!gts)
 630                 return -EINVAL;
 631
 632         gts->ts_tgid_owner = current->tgid;
 633         gru_unlock_gts(gts);
 634
 635         return 0;
 636 }