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Subject[patch 10/13] GRU Driver V2 - TLB flushing, MMUOPS callouts
This file contains the functions for handlinf GRU TLB flushing, This includes
functions to handle the MMUOPS callouts.


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

---
drivers/misc/sgi-gru/grutlbpurge.c | 370 +++++++++++++++++++++++++++++++++++++
1 file changed, 370 insertions(+)

Index: linux/drivers/misc/sgi-gru/grutlbpurge.c
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ linux/drivers/misc/sgi-gru/grutlbpurge.c 2008-06-14 18:51:47.534830739 -0500
@@ -0,0 +1,370 @@
+/*
+ * SN Platform GRU Driver
+ *
+ * MMUOPS callbacks + TLB flushing
+ *
+ * This file handles emu notifier callbacks from the core kernel. The callbacks
+ * are used to update the TLB in the GRU as a result of changes in the
+ * state of a process address space. This file also handles TLB invalidates
+ * from the GRU driver.
+ *
+ * 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/list.h>
+#include <linux/spinlock.h>
+#include <linux/mm.h>
+#include <linux/slab.h>
+#include <linux/device.h>
+#include <linux/hugetlb.h>
+#include <linux/delay.h>
+#include <linux/timex.h>
+#include <linux/delay.h>
+#include <linux/srcu.h>
+#include <asm/processor.h>
+#include "gru.h"
+#include "grutables.h"
+#include <asm/uv/uv_hub.h>
+
+#define gru_random() get_cycles()
+
+/* ---------------------------------- TLB Invalidation functions --------
+ * get_tgh_handle
+ *
+ * Find a TGH to use for issuing a TLB invalidate. For GRUs that are on the
+ * local blade, use a fixed TGH that is a function of the blade-local cpu
+ * number. Normally, this TGH is private to the cpu & no contention occurs for
+ * the TGH. For offblade GRUs, select a random TGH in the range above the
+ * private TGHs. A spinlock is required to access this TGH & the lock must be
+ * released when the invalidate is completes. This sucks, but it is the best we
+ * can do.
+ *
+ * Note that the spinlock is IN the TGH handle so locking does not involve
+ * additional cache lines.
+ *
+ */
+static inline int get_off_blade_tgh(struct gru_state *gru)
+{
+ int n;
+
+ n = GRU_NUM_TGH - gru->gs_tgh_first_remote;
+ n = gru_random() % n;
+ n += gru->gs_tgh_first_remote;
+ return n;
+}
+
+static inline int get_on_blade_tgh(struct gru_state *gru)
+{
+ return uv_blade_processor_id() >> gru->gs_tgh_local_shift;
+}
+
+static struct gru_tlb_global_handle *get_lock_tgh_handle(struct gru_state
+ *gru)
+{
+ struct gru_tlb_global_handle *tgh;
+ int n;
+
+ preempt_disable();
+ if (uv_numa_blade_id() == gru->gs_blade_id)
+ n = get_on_blade_tgh(gru);
+ else
+ n = get_off_blade_tgh(gru);
+ tgh = get_tgh_by_index(gru, n);
+ lock_tgh_handle(tgh);
+
+ return tgh;
+}
+
+static void get_unlock_tgh_handle(struct gru_tlb_global_handle *tgh)
+{
+ unlock_tgh_handle(tgh);
+ preempt_enable();
+}
+
+/*
+ * gru_flush_tlb_range
+ *
+ * General purpose TLB invalidation function. This function scans every GRU in
+ * the ENTIRE system (partition) looking for GRUs where the specified MM has
+ * been accessed by the GRU. For each GRU found, the TLB must be invalidated OR
+ * the ASID invalidated. Invalidating an ASID causes a new ASID to be assigned
+ * on the next fault. This effectively flushes the ENTIRE TLB for the MM at the
+ * cost of (possibly) a large number of future TLBmisses.
+ *
+ * The current algorithm is optimized based on the following (somewhat true)
+ * assumptions:
+ * - GRU contexts are not loaded into a GRU unless a reference is made to
+ * the data segment or control block (this is true, not an assumption).
+ * If a DS/CB is referenced, the user will also issue instructions that
+ * cause TLBmisses. It is not necessary to optimize for the case where
+ * contexts are loaded but no instructions cause TLB misses. (I know
+ * this will happen but I'm not optimizing for it).
+ * - GRU instructions to invalidate TLB entries are SLOOOOWWW - normally
+ * a few usec but in unusual cases, it could be longer. Avoid if
+ * possible.
+ * - intrablade process migration between cpus is not frequent but is
+ * common.
+ * - a GRU context is not typically migrated to a different GRU on the
+ * blade because of intrablade migration
+ * - interblade migration is rare. Processes migrate their GRU context to
+ * the new blade.
+ * - if interblade migration occurs, migration back to the original blade
+ * is very very rare (ie., no optimization for this case)
+ * - most GRU instruction operate on a subset of the user REGIONS. Code
+ * & shared library regions are not likely targets of GRU instructions.
+ *
+ * To help improve the efficiency of TLB invalidation, the GMS data
+ * structure is maintained for EACH address space (MM struct). The GMS is
+ * also the structure that contains the pointer to the mmu callout
+ * functions. This structure is linked to the mm_struct for the address space
+ * using the mmu "register" function. The mmu interfaces are used to
+ * provide the callbacks for TLB invalidation. The GMS contains:
+ *
+ * - asid[maxgrus] array. ASIDs are assigned to a GRU when a context is
+ * loaded into the GRU.
+ * - asidmap[maxgrus]. bitmap to make it easier to find non-zero asids in
+ * the above array
+ * - ctxbitmap[maxgrus]. Indicates the contexts that are currently active
+ * in the GRU for the address space. This bitmap must be passed to the
+ * GRU to do an invalidate.
+ *
+ * The current algorithm for invalidating TLBs is:
+ * - scan the asidmap for GRUs where the context has been loaded, ie,
+ * asid is non-zero.
+ * - for each gru found:
+ * - if the ctxtmap is non-zero, there are active contexts in the
+ * GRU. TLB invalidate instructions must be issued to the GRU.
+ * - if the ctxtmap is zero, no context is active. Set the ASID to
+ * zero to force a full TLB invalidation. This is fast but will
+ * cause a lot of TLB misses if the context is reloaded onto the
+ * GRU
+ *
+ */
+
+void gru_flush_tlb_range(struct gru_mm_struct *gms, unsigned long start,
+ unsigned long len)
+{
+ struct gru_state *gru;
+ struct gru_mm_tracker *asids;
+ struct gru_tlb_global_handle *tgh;
+ unsigned long num;
+ int grupagesize, pagesize, pageshift, gid, asid;
+
+ /* ZZZ TODO - handle huge pages */
+ pageshift = PAGE_SHIFT;
+ pagesize = (1UL << pageshift);
+ grupagesize = GRU_PAGESIZE(pageshift);
+ num = min(((len + pagesize - 1) >> pageshift), GRUMAXINVAL);
+
+ STAT(flush_tlb);
+ gru_dbg(grudev, "gms %p, start 0x%lx, len 0x%lx, asidmap 0x%lx\n", gms,
+ start, len, gms->ms_asidmap[0]);
+
+ spin_lock(&gms->ms_asid_lock);
+ for_each_gru_in_bitmap(gid, gms->ms_asidmap) {
+ STAT(flush_tlb_gru);
+ gru = GID_TO_GRU(gid);
+ asids = gms->ms_asids + gid;
+ asid = asids->mt_asid;
+ if (asids->mt_ctxbitmap && asid) {
+ STAT(flush_tlb_gru_tgh);
+ asid = GRUASID(asid, start);
+ gru_dbg(grudev,
+ " FLUSH gruid %d, asid 0x%x, num %ld, cbmap 0x%x\n",
+ gid, asid, num, asids->mt_ctxbitmap);
+ tgh = get_lock_tgh_handle(gru);
+ tgh_invalidate(tgh, start, 0, asid, grupagesize, 0,
+ num - 1, asids->mt_ctxbitmap);
+ get_unlock_tgh_handle(tgh);
+ } else {
+ STAT(flush_tlb_gru_zero_asid);
+ asids->mt_asid = 0;
+ __clear_bit(gru->gs_gid, gms->ms_asidmap);
+ gru_dbg(grudev,
+ " CLEARASID gruid %d, asid 0x%x, cbtmap 0x%x, asidmap 0x%lx\n",
+ gid, asid, asids->mt_ctxbitmap,
+ gms->ms_asidmap[0]);
+ }
+ }
+ spin_unlock(&gms->ms_asid_lock);
+}
+
+/*
+ * Flush the entire TLB on a chiplet.
+ */
+void gru_flush_all_tlb(struct gru_state *gru)
+{
+ struct gru_tlb_global_handle *tgh;
+
+ gru_dbg(grudev, "gru %p, gid %d\n", gru, gru->gs_gid);
+ tgh = get_lock_tgh_handle(gru);
+ tgh_invalidate(tgh, 0, ~0, 0, 1, 1, GRUMAXINVAL - 1, 0);
+ get_unlock_tgh_handle(tgh);
+ preempt_enable();
+}
+
+/*
+ * MMUOPS notifier callout functions
+ */
+static void gru_invalidate_range_start(struct mmu_notifier *mn,
+ struct mm_struct *mm,
+ unsigned long start, unsigned long end)
+{
+ struct gru_mm_struct *gms = container_of(mn, struct gru_mm_struct,
+ ms_notifier);
+
+ STAT(mmu_invalidate_range);
+ atomic_inc(&gms->ms_range_active);
+ gru_dbg(grudev, "gms %p, start 0x%lx, end 0x%lx, act %d\n", gms,
+ start, end, atomic_read(&gms->ms_range_active));
+ gru_flush_tlb_range(gms, start, end - start);
+}
+
+static void gru_invalidate_range_end(struct mmu_notifier *mn,
+ struct mm_struct *mm, unsigned long start,
+ unsigned long end)
+{
+ struct gru_mm_struct *gms = container_of(mn, struct gru_mm_struct,
+ ms_notifier);
+
+ atomic_dec(&gms->ms_range_active);
+ wake_up_all(&gms->ms_wait_queue);
+ gru_dbg(grudev, "gms %p, start 0x%lx, end 0x%lx\n", gms, start, end);
+}
+
+static void gru_invalidate_page(struct mmu_notifier *mn, struct mm_struct *mm,
+ unsigned long address)
+{
+ struct gru_mm_struct *gms = container_of(mn, struct gru_mm_struct,
+ ms_notifier);
+
+ STAT(mmu_invalidate_page);
+ gru_flush_tlb_range(gms, address, PAGE_SIZE);
+ gru_dbg(grudev, "gms %p, address 0x%lx\n", gms, address);
+}
+
+static void gru_release(struct mmu_notifier *mn, struct mm_struct *mm)
+{
+ struct gru_mm_struct *gms = container_of(mn, struct gru_mm_struct,
+ ms_notifier);
+
+ gms->ms_released = 1;
+ gru_dbg(grudev, "gms %p\n", gms);
+}
+
+
+static const struct mmu_notifier_ops gru_mmuops = {
+ .invalidate_page = gru_invalidate_page,
+ .invalidate_range_start = gru_invalidate_range_start,
+ .invalidate_range_end = gru_invalidate_range_end,
+ .release = gru_release,
+};
+
+/* Move this to the basic mmu_notifier file. But for now... */
+static struct mmu_notifier *mmu_find_ops(struct mm_struct *mm,
+ const struct mmu_notifier_ops *ops)
+{
+ struct mmu_notifier *mn, *gru_mn = NULL;
+ struct hlist_node *n;
+
+ if (mm->mmu_notifier_mm) {
+ rcu_read_lock();
+ hlist_for_each_entry_rcu(mn, n, &mm->mmu_notifier_mm->list,
+ hlist)
+ if (mn->ops == ops) {
+ gru_mn = mn;
+ break;
+ }
+ rcu_read_unlock();
+ }
+ return gru_mn;
+}
+
+struct gru_mm_struct *gru_register_mmu_notifier(void)
+{
+ struct gru_mm_struct *gms;
+ struct mmu_notifier *mn;
+
+ mn = mmu_find_ops(current->mm, &gru_mmuops);
+ if (mn) {
+ gms = container_of(mn, struct gru_mm_struct, ms_notifier);
+ atomic_inc(&gms->ms_refcnt);
+ } else {
+ gms = kzalloc(sizeof(*gms), GFP_KERNEL);
+ if (gms) {
+ spin_lock_init(&gms->ms_asid_lock);
+ gms->ms_notifier.ops = &gru_mmuops;
+ atomic_set(&gms->ms_refcnt, 1);
+ init_waitqueue_head(&gms->ms_wait_queue);
+ __mmu_notifier_register(&gms->ms_notifier, current->mm);
+ }
+ }
+ gru_dbg(grudev, "gms %p, refcnt %d\n", gms,
+ atomic_read(&gms->ms_refcnt));
+ return gms;
+}
+
+void gru_drop_mmu_notifier(struct gru_mm_struct *gms)
+{
+ gru_dbg(grudev, "gms %p, refcnt %d, released %d\n", gms,
+ atomic_read(&gms->ms_refcnt), gms->ms_released);
+ if (atomic_dec_return(&gms->ms_refcnt) == 0) {
+ if (!gms->ms_released)
+ mmu_notifier_unregister(&gms->ms_notifier, current->mm);
+ kfree(gms);
+ }
+}
+
+/*
+ * Setup TGH parameters. There are:
+ * - 24 TGH handles per GRU chiplet
+ * - a portion (MAX_LOCAL_TGH) of the handles are reserved for
+ * use by blade-local cpus
+ * - the rest are used by off-blade cpus. This usage is
+ * less frequent than blade-local usage.
+ *
+ * For now, use 16 handles for local flushes, 8 for remote flushes. If the blade
+ * has less tan or equal to 16 cpus, each cpu has a unique handle that it can
+ * use.
+ */
+#define MAX_LOCAL_TGH 16
+
+void gru_tgh_flush_init(struct gru_state *gru)
+{
+ int cpus, shift = 0, n;
+
+ cpus = uv_blade_nr_possible_cpus(gru->gs_blade_id);
+
+ /* n = cpus rounded up to next power of 2 */
+ if (cpus) {
+ n = 1 << fls(cpus - 1);
+
+ /*
+ * shift count for converting local cpu# to TGH index
+ * 0 if cpus <= MAX_LOCAL_TGH,
+ * 1 if cpus <= 2*MAX_LOCAL_TGH,
+ * etc
+ */
+ shift = max(0, fls(n - 1) - fls(MAX_LOCAL_TGH - 1));
+ }
+ gru->gs_tgh_local_shift = shift;
+
+ /* first starting TGH index to use for remote purges */
+ gru->gs_tgh_first_remote = (cpus + (1 << shift) - 1) >> shift;
+
+}
--


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