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Subject[patch 06/13] GRU Driver V2 - page faults & exceptions
This file contains the functions that manage GRU page faults and exceptions. 


Signed-off-by: Jack Steiner <steiner@sgi.com>

---
drivers/misc/sgi-gru/grufault.c | 597 ++++++++++++++++++++++++++++++++++++++++
1 file changed, 597 insertions(+)
Index: linux/drivers/misc/sgi-gru/grufault.c
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ linux/drivers/misc/sgi-gru/grufault.c 2008-06-14 18:51:47.354808360 -0500
@@ -0,0 +1,597 @@
+/*
+ * SN Platform GRU Driver
+ *
+ * FAULT HANDLER FOR GRU DETECTED TLB MISSES
+ *
+ * This file contains code that handles TLB misses within the GRU.
+ * These misses are reported either via interrupts or user polling of
+ * the user CB.
+ *
+ * Copyright (c) 2008 Silicon Graphics, Inc. All Rights Reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ */
+
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/spinlock.h>
+#include <linux/mm.h>
+#include <linux/hugetlb.h>
+#include <linux/device.h>
+#include <linux/io.h>
+#include <linux/uaccess.h>
+#include <asm/pgtable.h>
+#include "gru.h"
+#include "grutables.h"
+#include "grulib.h"
+#include "gru_instructions.h"
+#include <asm/uv/uv_hub.h>
+
+/*
+ * Test if a physical address is a valid GRU GSEG address
+ */
+static inline int is_gru_paddr(unsigned long paddr)
+{
+ return paddr >= gru_start_paddr && paddr < gru_end_paddr;
+}
+
+/*
+ * Find the vma of a GRU segment. Caller must hold mmap_sem.
+ */
+struct vm_area_struct *gru_find_vma(unsigned long vaddr)
+{
+ struct vm_area_struct *vma;
+
+ vma = find_vma(current->mm, vaddr);
+ if (vma && vma->vm_start <= vaddr && vma->vm_ops == &gru_vm_ops)
+ return vma;
+ return NULL;
+}
+
+/*
+ * Find and lock the gts that contains the specified user vaddr.
+ *
+ * Returns:
+ * - *gts with the mmap_sem locked for read and the GTS locked.
+ * - NULL if vaddr invalid OR is not a valid GSEG vaddr.
+ */
+
+static struct gru_thread_state *gru_find_lock_gts(unsigned long vaddr)
+{
+ struct mm_struct *mm = current->mm;
+ struct vm_area_struct *vma;
+ struct gru_thread_state *gts = NULL;
+
+ down_read(&mm->mmap_sem);
+ vma = gru_find_vma(vaddr);
+ if (vma)
+ gts = gru_find_thread_state(vma, TSID(vaddr, vma));
+ if (gts)
+ mutex_lock(&gts->ts_ctxlock);
+ else
+ up_read(&mm->mmap_sem);
+ return gts;
+}
+
+static struct gru_thread_state *gru_alloc_locked_gts(unsigned long vaddr)
+{
+ struct mm_struct *mm = current->mm;
+ struct vm_area_struct *vma;
+ struct gru_thread_state *gts = NULL;
+
+ down_write(&mm->mmap_sem);
+ vma = gru_find_vma(vaddr);
+ if (vma)
+ gts = gru_alloc_thread_state(vma, TSID(vaddr, vma));
+ if (gts) {
+ mutex_lock(&gts->ts_ctxlock);
+ downgrade_write(&mm->mmap_sem);
+ } else {
+ up_write(&mm->mmap_sem);
+ }
+
+ return gts;
+}
+
+/*
+ * Unlock a GTS that was previously locked with gru_find_lock_gts().
+ */
+static void gru_unlock_gts(struct gru_thread_state *gts)
+{
+ mutex_unlock(&gts->ts_ctxlock);
+ up_read(&current->mm->mmap_sem);
+}
+
+/*
+ * Set a CB.istatus to active using a user virtual address. This must be done
+ * just prior to a TFH RESTART. The new cb.istatus is an in-cache status ONLY.
+ * If the line is evicted, the status may be lost. The in-cache update
+ * is necessary to prevent the user from seeing a stale cb.istatus that will
+ * change as soon as the TFH restart is complete. Races may cause an
+ * occasional failure to clear the cb.istatus, but that is ok.
+ *
+ * If the cb address is not valid (should not happen, but...), nothing
+ * bad will happen.. The get_user()/put_user() will fail but there
+ * are no bad side-effects.
+ */
+static void gru_cb_set_istatus_active(unsigned long __user *cb)
+{
+ union {
+ struct gru_instruction_bits bits;
+ unsigned long dw;
+ } u;
+
+ if (cb) {
+ get_user(u.dw, cb);
+ u.bits.istatus = CBS_ACTIVE;
+ put_user(u.dw, cb);
+ }
+}
+
+/*
+ * Convert a interrupt IRQ to a pointer to the GRU GTS that caused the
+ * interrupt. Interrupts are always sent to a cpu on the blade that contains the
+ * GRU (except for headless blades which are not currently supported). A blade
+ * has N grus; a block of N consecutive IRQs is assigned to the GRUs. The IRQ
+ * number uniquely identifies the GRU chiplet on the local blade that caused the
+ * interrupt. Always called in interrupt context.
+ */
+static inline struct gru_state *irq_to_gru(int irq)
+{
+ return &gru_base[uv_numa_blade_id()]->bs_grus[irq - IRQ_GRU];
+}
+
+/*
+ * Read & clear a TFM
+ *
+ * The GRU has an array of fault maps. A map is private to a cpu
+ * Only one cpu will be accessing a cpu's fault map.
+ *
+ * This function scans the cpu-private fault map & clears all bits that
+ * are set. The function returns a bitmap that indicates the bits that
+ * were cleared. Note that sense the maps may be updated asynchronously by
+ * the GRU, atomic operations must be used to clear bits.
+ */
+static void get_clear_fault_map(struct gru_state *gru,
+ struct gru_tlb_fault_map *map)
+{
+ unsigned long i, k;
+ struct gru_tlb_fault_map *tfm;
+
+ tfm = get_tfm_for_cpu(gru, gru_cpu_fault_map_id());
+ prefetchw(tfm); /* Helps on hardware, required for emulator */
+ for (i = 0; i < BITS_TO_LONGS(GRU_NUM_CBE); i++) {
+ k = tfm->fault_bits[i];
+ if (k)
+ k = xchg(&tfm->fault_bits[i], 0UL);
+ map->fault_bits[i] = k;
+ }
+
+ /*
+ * Not functionally required but helps performance. (Required
+ * on emulator)
+ */
+ gru_flush_cache(tfm);
+}
+
+/*
+ * Atomic (interrupt context) & non-atomic (user context) functions to
+ * convert a vaddr into a physical address. The sise of the page
+ * is returned in pageshift.
+ * returns:
+ * 0 - successful
+ * < 0 - error code
+ * 1 - (atomic only) try again in non-atomic context
+ */
+static int non_atomic_pte_lookup(struct vm_area_struct *vma,
+ unsigned long vaddr, int write,
+ unsigned long *paddr, int *pageshift)
+{
+ struct page *page;
+
+ /* ZZZ Need to handle HUGE pages */
+ if (is_vm_hugetlb_page(vma))
+ return -EFAULT;
+ *pageshift = PAGE_SHIFT;
+ if (get_user_pages
+ (current, current->mm, vaddr, 1, write, 1, &page, NULL) <= 0)
+ return -EFAULT;
+ *paddr = page_to_phys(page);
+ put_page(page);
+ return 0;
+}
+
+static int atomic_pte_lookup(struct vm_area_struct *vma, unsigned long vaddr,
+ int write, unsigned long *paddr, int *pageshift)
+{
+ struct page *page;
+
+ /* ZZZ Need to handle HUGE pages */
+ if (is_vm_hugetlb_page(vma))
+ return -EFAULT;
+ *pageshift = PAGE_SHIFT;
+ page = follow_page(vma, vaddr, (write ? FOLL_WRITE : 0));
+ if (!page)
+ return 1;
+ *paddr = page_to_phys(page);
+ return 0;
+}
+
+/*
+ * Drop a TLB entry into the GRU. The fault is described by info in an TFH.
+ * Input:
+ * cb Address of user CBR. Null if not running in user context
+ * Return:
+ * 0 = dropin, exception, or switch to UPM successful
+ * 1 = range invalidate active
+ * < 0 = error code
+ *
+ */
+static int gru_try_dropin(struct gru_thread_state *gts,
+ struct gru_tlb_fault_handle *tfh,
+ unsigned long __user *cb)
+{
+ struct mm_struct *mm = gts->ts_mm;
+ struct vm_area_struct *vma;
+ int pageshift, asid, write, ret;
+ unsigned long paddr, gpa, vaddr;
+
+ /*
+ * NOTE: The GRU contains magic hardware that eliminates races between
+ * TLB invalidates and TLB dropins. If an invalidate occurs
+ * in the window between reading the TFH and the subsequent TLB dropin,
+ * the dropin is ignored. This eliminates the need for additional locks.
+ */
+
+ /*
+ * Error if TFH state is IDLE or FMM mode & the user issuing a UPM call.
+ * Might be a hardware race OR a stupid user. Ignore FMM because FMM
+ * is a transient state.
+ */
+ if (tfh->state == TFHSTATE_IDLE)
+ goto failidle;
+ if (tfh->state == TFHSTATE_MISS_FMM && cb)
+ goto failfmm;
+
+ write = (tfh->cause & TFHCAUSE_TLB_MOD) != 0;
+ vaddr = tfh->missvaddr;
+ asid = tfh->missasid;
+ if (asid == 0)
+ goto failnoasid;
+
+ rmb(); /* TFH must be cache resident before reading ms_range_active */
+
+ /*
+ * TFH is cache resident - at least briefly. Fail the dropin
+ * if a range invalidate is active.
+ */
+ if (atomic_read(&gts->ts_gms->ms_range_active))
+ goto failactive;
+
+ vma = find_vma(mm, vaddr);
+ if (!vma)
+ goto failinval;
+
+ /*
+ * Atomic lookup is faster & usually works even if called in non-atomic
+ * context.
+ */
+ ret = atomic_pte_lookup(vma, vaddr, write, &paddr, &pageshift);
+ if (ret) {
+ if (!cb)
+ goto failupm;
+ if (non_atomic_pte_lookup(vma, vaddr, write, &paddr,
+ &pageshift))
+ goto failinval;
+ }
+ if (is_gru_paddr(paddr))
+ goto failinval;
+
+ paddr = paddr & ~((1UL << pageshift) - 1);
+ gpa = uv_soc_phys_ram_to_gpa(paddr);
+ gru_cb_set_istatus_active(cb);
+ tfh_write_restart(tfh, gpa, GAA_RAM, vaddr, asid, write,
+ GRU_PAGESIZE(pageshift));
+ STAT(tlb_dropin);
+ gru_dbg(grudev,
+ "%s: tfh 0x%p, vaddr 0x%lx, asid 0x%x, ps %d, gpa 0x%lx\n",
+ ret ? "non-atomic" : "atomic", tfh, vaddr, asid,
+ pageshift, gpa);
+ return 0;
+
+failnoasid:
+ /* No asid (delayed unload). */
+ STAT(tlb_dropin_fail_no_asid);
+ gru_dbg(grudev, "FAILED no_asid tfh: 0x%p, vaddr 0x%lx\n", tfh, vaddr);
+ if (!cb)
+ tfh_user_polling_mode(tfh);
+ else
+ gru_flush_cache(tfh);
+ return -EAGAIN;
+
+failupm:
+ /* Atomic failure switch CBR to UPM */
+ tfh_user_polling_mode(tfh);
+ STAT(tlb_dropin_fail_upm);
+ gru_dbg(grudev, "FAILED upm tfh: 0x%p, vaddr 0x%lx\n", tfh, vaddr);
+ return 1;
+
+failfmm:
+ /* FMM state on UPM call */
+ STAT(tlb_dropin_fail_fmm);
+ gru_dbg(grudev, "FAILED fmm tfh: 0x%p, state %d\n", tfh, tfh->state);
+ return 0;
+
+failidle:
+ /* TFH was idle - no miss pending */
+ gru_flush_cache(tfh);
+ if (cb)
+ gru_flush_cache(cb);
+ STAT(tlb_dropin_fail_idle);
+ gru_dbg(grudev, "FAILED idle tfh: 0x%p, state %d\n", tfh, tfh->state);
+ return 0;
+
+failinval:
+ /* All errors (atomic & non-atomic) switch CBR to EXCEPTION state */
+ tfh_exception(tfh);
+ STAT(tlb_dropin_fail_invalid);
+ gru_dbg(grudev, "FAILED inval tfh: 0x%p, vaddr 0x%lx\n", tfh, vaddr);
+ return -EFAULT;
+
+failactive:
+ /* Range invalidate active. Switch to UPM iff atomic */
+ if (!cb)
+ tfh_user_polling_mode(tfh);
+ else
+ gru_flush_cache(tfh);
+ STAT(tlb_dropin_fail_range_active);
+ gru_dbg(grudev, "FAILED range active: tfh 0x%p, vaddr 0x%lx\n",
+ tfh, vaddr);
+ return 1;
+}
+
+/*
+ * Process an external interrupt from the GRU. This interrupt is
+ * caused by a TLB miss.
+ * Note that this is the interrupt handler that is registered with linux
+ * interrupt handlers.
+ */
+irqreturn_t gru_intr(int irq, void *dev_id)
+{
+ struct gru_state *gru;
+ struct gru_tlb_fault_map map;
+ struct gru_thread_state *gts;
+ struct gru_tlb_fault_handle *tfh = NULL;
+ int cbrnum, ctxnum;
+
+ STAT(intr);
+
+ gru = irq_to_gru(irq);
+ if (!gru) {
+ dev_err(grudev, "GRU: invalid interrupt: cpu %d, irq %d\n",
+ raw_smp_processor_id(), irq);
+ return IRQ_NONE;
+ }
+ get_clear_fault_map(gru, &map);
+ gru_dbg(grudev, "irq %d, gru %x, map 0x%lx\n", irq, gru->gs_gid,
+ map.fault_bits[0]);
+
+ for_each_cbr_in_tfm(cbrnum, map.fault_bits) {
+ tfh = get_tfh_by_index(gru, cbrnum);
+ prefetchw(tfh); /* Helps on hdw, required for emulator */
+
+ /*
+ * When hardware sets a bit in the faultmap, it implicitly
+ * locks the GRU context so that it cannot be unloaded.
+ * The gts cannot change until a TFH start/writestart command
+ * is issued.
+ */
+ ctxnum = tfh->ctxnum;
+ gts = gru->gs_gts[ctxnum];
+
+ /*
+ * This is running in interrupt context. Trylock the mmap_sem.
+ * If it fails, retry the fault in user context.
+ */
+ if (down_read_trylock(&gts->ts_mm->mmap_sem)) {
+ gru_try_dropin(gts, tfh, NULL);
+ up_read(&gts->ts_mm->mmap_sem);
+ } else {
+ tfh_user_polling_mode(tfh);
+ }
+ }
+ return IRQ_HANDLED;
+}
+
+
+static int gru_user_dropin(struct gru_thread_state *gts,
+ struct gru_tlb_fault_handle *tfh,
+ unsigned long __user *cb)
+{
+ struct gru_mm_struct *gms = gts->ts_gms;
+ int ret;
+
+ while (1) {
+ wait_event(gms->ms_wait_queue,
+ atomic_read(&gms->ms_range_active) == 0);
+ prefetchw(tfh); /* Helps on hdw, required for emulator */
+ ret = gru_try_dropin(gts, tfh, cb);
+ if (ret <= 0)
+ return ret;
+ STAT(call_os_wait_queue);
+ }
+}
+
+/*
+ * This interface is called as a result of a user detecting a "call OS" bit
+ * in a user CB. Normally means that a TLB fault has occurred.
+ * cb - user virtual address of the CB
+ */
+int gru_handle_user_call_os(unsigned long cb)
+{
+ struct gru_tlb_fault_handle *tfh;
+ struct gru_thread_state *gts;
+ unsigned long __user *cbp;
+ int ucbnum, cbrnum, ret = -EINVAL;
+
+ STAT(call_os);
+ gru_dbg(grudev, "address 0x%lx\n", cb);
+
+ /* sanity check the cb pointer */
+ ucbnum = get_cb_number((void *)cb);
+ if ((cb & (GRU_HANDLE_STRIDE - 1)) || ucbnum >= GRU_NUM_CB)
+ return -EINVAL;
+ cbp = (unsigned long *)cb;
+
+ gts = gru_find_lock_gts(cb);
+ if (!gts)
+ return -EINVAL;
+
+ if (ucbnum >= gts->ts_cbr_au_count * GRU_CBR_AU_SIZE) {
+ ret = -EINVAL;
+ goto exit;
+ }
+
+ /*
+ * If force_unload is set, the UPM TLB fault is phony. The task
+ * has migrated to another node and the GSEG must be moved. Just
+ * unload the context. The task will page fault and assign a new
+ * context.
+ */
+ ret = -EAGAIN;
+ cbrnum = thread_cbr_number(gts, ucbnum);
+ if (gts->ts_force_unload) {
+ gru_unload_context(gts, 1);
+ } else if (gts->ts_gru) {
+ tfh = get_tfh_by_index(gts->ts_gru, cbrnum);
+ ret = gru_user_dropin(gts, tfh, cbp);
+ }
+exit:
+ gru_unlock_gts(gts);
+ return ret;
+}
+
+/*
+ * Fetch the exception detail information for a CB that terminated with
+ * an exception.
+ */
+int gru_get_exception_detail(unsigned long arg)
+{
+ struct control_block_extended_exc_detail excdet;
+ struct gru_control_block_extended *cbe;
+ struct gru_thread_state *gts;
+ int ucbnum, cbrnum, ret;
+
+ STAT(user_exception);
+ if (copy_from_user(&excdet, (void __user *)arg, sizeof(excdet)))
+ return -EFAULT;
+
+ gru_dbg(grudev, "address 0x%lx\n", excdet.cb);
+ gts = gru_find_lock_gts(excdet.cb);
+ if (!gts)
+ return -EINVAL;
+
+ if (gts->ts_gru) {
+ ucbnum = get_cb_number((void *)excdet.cb);
+ cbrnum = thread_cbr_number(gts, ucbnum);
+ cbe = get_cbe_by_index(gts->ts_gru, cbrnum);
+ excdet.opc = cbe->opccpy;
+ excdet.exopc = cbe->exopccpy;
+ excdet.ecause = cbe->ecause;
+ excdet.exceptdet0 = cbe->idef1upd;
+ excdet.exceptdet1 = cbe->idef3upd;
+ ret = 0;
+ } else {
+ ret = -EAGAIN;
+ }
+ gru_unlock_gts(gts);
+
+ gru_dbg(grudev, "address 0x%lx, ecause 0x%x\n", excdet.cb,
+ excdet.ecause);
+ if (!ret && copy_to_user((void __user *)arg, &excdet, sizeof(excdet)))
+ ret = -EFAULT;
+ return ret;
+}
+
+/*
+ * User request to unload a context. Content is saved for possible reload.
+ */
+int gru_user_unload_context(unsigned long arg)
+{
+ struct gru_thread_state *gts;
+ struct gru_unload_context_req req;
+
+ STAT(user_unload_context);
+ if (copy_from_user(&req, (void __user *)arg, sizeof(req)))
+ return -EFAULT;
+
+ gru_dbg(grudev, "gseg 0x%lx\n", req.gseg);
+
+ gts = gru_find_lock_gts(req.gseg);
+ if (!gts)
+ return -EINVAL;
+
+ if (gts->ts_gru)
+ gru_unload_context(gts, 1);
+ gru_unlock_gts(gts);
+
+ return 0;
+}
+
+/*
+ * User request to flush a range of virtual addresses from the GRU TLB
+ * (Mainly for testing).
+ */
+int gru_user_flush_tlb(unsigned long arg)
+{
+ struct gru_thread_state *gts;
+ struct gru_flush_tlb_req req;
+
+ STAT(user_flush_tlb);
+ if (copy_from_user(&req, (void __user *)arg, sizeof(req)))
+ return -EFAULT;
+
+ gru_dbg(grudev, "gseg 0x%lx, vaddr 0x%lx, len 0x%lx\n", req.gseg,
+ req.vaddr, req.len);
+
+ gts = gru_find_lock_gts(req.gseg);
+ if (!gts)
+ return -EINVAL;
+
+ gru_flush_tlb_range(gts->ts_gms, req.vaddr, req.vaddr + req.len);
+ gru_unlock_gts(gts);
+
+ return 0;
+}
+
+/*
+ * Register the current task as the user of the GSEG slice.
+ * Needed for TLB fault interrupt targeting.
+ */
+int gru_set_task_slice(long address)
+{
+ struct gru_thread_state *gts;
+
+ STAT(set_task_slice);
+ gru_dbg(grudev, "address 0x%lx\n", address);
+ gts = gru_alloc_locked_gts(address);
+ if (!gts)
+ return -EINVAL;
+
+ gts->ts_tgid_owner = current->tgid;
+ gru_unlock_gts(gts);
+
+ return 0;
+}
--


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