// SPDX-License-Identifier: GPL-2.0-or-later
/*
* 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.
*/
#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/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, vaddr 0x%lx, vamask 0x%x, num %ld, cbmap 0x%x\n",
gid, asid, start, grupagesize, 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, "gid %d\n", gru->gs_gid);
tgh = get_lock_tgh_handle(gru);
tgh_invalidate(tgh, 0, ~0, 0, 1, 1, GRUMAXINVAL - 1, 0xffff);
get_unlock_tgh_handle(tgh);
}
/*
* MMUOPS notifier callout functions
*/
static int gru_invalidate_range_start(struct mmu_notifier *mn,
const struct mmu_notifier_range *range)
{
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,
range->start, range->end, atomic_read(&gms->ms_range_active));
gru_flush_tlb_range(gms, range->start, range->end - range->start);
return 0;
}
static void gru_invalidate_range_end(struct mmu_notifier *mn,
const struct mmu_notifier_range *range)
{
struct gru_mm_struct *gms = container_of(mn, struct gru_mm_struct,
ms_notifier);
/* ..._and_test() provides needed barrier */
(void)atomic_dec_and_test(&gms->ms_range_active);
wake_up_all(&gms->ms_wait_queue);
gru_dbg(grudev, "gms %p, start 0x%lx, end 0x%lx\n",
gms, range->start, range->end);
}
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_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;
if (mm->mmu_notifier_mm) {
rcu_read_lock();
hlist_for_each_entry_rcu(mn, &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;
int err;
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)
return ERR_PTR(-ENOMEM);
STAT(gms_alloc);
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);
err = __mmu_notifier_register(&gms->ms_notifier, current->mm);
if (err)
goto error;
}
if (gms)
gru_dbg(grudev, "gms %p, refcnt %d\n", gms,
atomic_read(&gms->ms_refcnt));
return gms;
error:
kfree(gms);
return ERR_PTR(err);
}
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);
STAT(gms_free);
}
}
/*
* 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;
}
