* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
- * version 2 of the License, or (at your option) any later version.
+ * version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
QEMU_BUILD_BUG_ON(NB_MMU_MODES > 16);
#define ALL_MMUIDX_BITS ((1 << NB_MMU_MODES) - 1)
+static inline size_t sizeof_tlb(CPUArchState *env, uintptr_t mmu_idx)
+{
+ return env->tlb_mask[mmu_idx] + (1 << CPU_TLB_ENTRY_BITS);
+}
+
+static void tlb_window_reset(CPUTLBWindow *window, int64_t ns,
+ size_t max_entries)
+{
+ window->begin_ns = ns;
+ window->max_entries = max_entries;
+}
+
+static void tlb_dyn_init(CPUArchState *env)
+{
+ int i;
+
+ for (i = 0; i < NB_MMU_MODES; i++) {
+ CPUTLBDesc *desc = &env->tlb_d[i];
+ size_t n_entries = 1 << CPU_TLB_DYN_DEFAULT_BITS;
+
+ tlb_window_reset(&desc->window, get_clock_realtime(), 0);
+ desc->n_used_entries = 0;
+ env->tlb_mask[i] = (n_entries - 1) << CPU_TLB_ENTRY_BITS;
+ env->tlb_table[i] = g_new(CPUTLBEntry, n_entries);
+ env->iotlb[i] = g_new(CPUIOTLBEntry, n_entries);
+ }
+}
+
+/**
+ * tlb_mmu_resize_locked() - perform TLB resize bookkeeping; resize if necessary
+ * @env: CPU that owns the TLB
+ * @mmu_idx: MMU index of the TLB
+ *
+ * Called with tlb_lock_held.
+ *
+ * We have two main constraints when resizing a TLB: (1) we only resize it
+ * on a TLB flush (otherwise we'd have to take a perf hit by either rehashing
+ * the array or unnecessarily flushing it), which means we do not control how
+ * frequently the resizing can occur; (2) we don't have access to the guest's
+ * future scheduling decisions, and therefore have to decide the magnitude of
+ * the resize based on past observations.
+ *
+ * In general, a memory-hungry process can benefit greatly from an appropriately
+ * sized TLB, since a guest TLB miss is very expensive. This doesn't mean that
+ * we just have to make the TLB as large as possible; while an oversized TLB
+ * results in minimal TLB miss rates, it also takes longer to be flushed
+ * (flushes can be _very_ frequent), and the reduced locality can also hurt
+ * performance.
+ *
+ * To achieve near-optimal performance for all kinds of workloads, we:
+ *
+ * 1. Aggressively increase the size of the TLB when the use rate of the
+ * TLB being flushed is high, since it is likely that in the near future this
+ * memory-hungry process will execute again, and its memory hungriness will
+ * probably be similar.
+ *
+ * 2. Slowly reduce the size of the TLB as the use rate declines over a
+ * reasonably large time window. The rationale is that if in such a time window
+ * we have not observed a high TLB use rate, it is likely that we won't observe
+ * it in the near future. In that case, once a time window expires we downsize
+ * the TLB to match the maximum use rate observed in the window.
+ *
+ * 3. Try to keep the maximum use rate in a time window in the 30-70% range,
+ * since in that range performance is likely near-optimal. Recall that the TLB
+ * is direct mapped, so we want the use rate to be low (or at least not too
+ * high), since otherwise we are likely to have a significant amount of
+ * conflict misses.
+ */
+static void tlb_mmu_resize_locked(CPUArchState *env, int mmu_idx)
+{
+ CPUTLBDesc *desc = &env->tlb_d[mmu_idx];
+ size_t old_size = tlb_n_entries(env, mmu_idx);
+ size_t rate;
+ size_t new_size = old_size;
+ int64_t now = get_clock_realtime();
+ int64_t window_len_ms = 100;
+ int64_t window_len_ns = window_len_ms * 1000 * 1000;
+ bool window_expired = now > desc->window.begin_ns + window_len_ns;
+
+ if (desc->n_used_entries > desc->window.max_entries) {
+ desc->window.max_entries = desc->n_used_entries;
+ }
+ rate = desc->window.max_entries * 100 / old_size;
+
+ if (rate > 70) {
+ new_size = MIN(old_size << 1, 1 << CPU_TLB_DYN_MAX_BITS);
+ } else if (rate < 30 && window_expired) {
+ size_t ceil = pow2ceil(desc->window.max_entries);
+ size_t expected_rate = desc->window.max_entries * 100 / ceil;
+
+ /*
+ * Avoid undersizing when the max number of entries seen is just below
+ * a pow2. For instance, if max_entries == 1025, the expected use rate
+ * would be 1025/2048==50%. However, if max_entries == 1023, we'd get
+ * 1023/1024==99.9% use rate, so we'd likely end up doubling the size
+ * later. Thus, make sure that the expected use rate remains below 70%.
+ * (and since we double the size, that means the lowest rate we'd
+ * expect to get is 35%, which is still in the 30-70% range where
+ * we consider that the size is appropriate.)
+ */
+ if (expected_rate > 70) {
+ ceil *= 2;
+ }
+ new_size = MAX(ceil, 1 << CPU_TLB_DYN_MIN_BITS);
+ }
+
+ if (new_size == old_size) {
+ if (window_expired) {
+ tlb_window_reset(&desc->window, now, desc->n_used_entries);
+ }
+ return;
+ }
+
+ g_free(env->tlb_table[mmu_idx]);
+ g_free(env->iotlb[mmu_idx]);
+
+ tlb_window_reset(&desc->window, now, 0);
+ /* desc->n_used_entries is cleared by the caller */
+ env->tlb_mask[mmu_idx] = (new_size - 1) << CPU_TLB_ENTRY_BITS;
+ env->tlb_table[mmu_idx] = g_try_new(CPUTLBEntry, new_size);
+ env->iotlb[mmu_idx] = g_try_new(CPUIOTLBEntry, new_size);
+ /*
+ * If the allocations fail, try smaller sizes. We just freed some
+ * memory, so going back to half of new_size has a good chance of working.
+ * Increased memory pressure elsewhere in the system might cause the
+ * allocations to fail though, so we progressively reduce the allocation
+ * size, aborting if we cannot even allocate the smallest TLB we support.
+ */
+ while (env->tlb_table[mmu_idx] == NULL || env->iotlb[mmu_idx] == NULL) {
+ if (new_size == (1 << CPU_TLB_DYN_MIN_BITS)) {
+ error_report("%s: %s", __func__, strerror(errno));
+ abort();
+ }
+ new_size = MAX(new_size >> 1, 1 << CPU_TLB_DYN_MIN_BITS);
+ env->tlb_mask[mmu_idx] = (new_size - 1) << CPU_TLB_ENTRY_BITS;
+
+ g_free(env->tlb_table[mmu_idx]);
+ g_free(env->iotlb[mmu_idx]);
+ env->tlb_table[mmu_idx] = g_try_new(CPUTLBEntry, new_size);
+ env->iotlb[mmu_idx] = g_try_new(CPUIOTLBEntry, new_size);
+ }
+}
+
+static inline void tlb_table_flush_by_mmuidx(CPUArchState *env, int mmu_idx)
+{
+ tlb_mmu_resize_locked(env, mmu_idx);
+ memset(env->tlb_table[mmu_idx], -1, sizeof_tlb(env, mmu_idx));
+ env->tlb_d[mmu_idx].n_used_entries = 0;
+}
+
+static inline void tlb_n_used_entries_inc(CPUArchState *env, uintptr_t mmu_idx)
+{
+ env->tlb_d[mmu_idx].n_used_entries++;
+}
+
+static inline void tlb_n_used_entries_dec(CPUArchState *env, uintptr_t mmu_idx)
+{
+ env->tlb_d[mmu_idx].n_used_entries--;
+}
+
void tlb_init(CPUState *cpu)
{
CPUArchState *env = cpu->env_ptr;
/* Ensure that cpu_reset performs a full flush. */
env->tlb_c.dirty = ALL_MMUIDX_BITS;
+
+ tlb_dyn_init(env);
}
/* flush_all_helper: run fn across all cpus
static void tlb_flush_one_mmuidx_locked(CPUArchState *env, int mmu_idx)
{
- memset(env->tlb_table[mmu_idx], -1, sizeof(env->tlb_table[0]));
+ tlb_table_flush_by_mmuidx(env, mmu_idx);
memset(env->tlb_v_table[mmu_idx], -1, sizeof(env->tlb_v_table[0]));
env->tlb_d[mmu_idx].large_page_addr = -1;
env->tlb_d[mmu_idx].large_page_mask = -1;
tlb_hit_page(tlb_entry->addr_code, page);
}
+/**
+ * tlb_entry_is_empty - return true if the entry is not in use
+ * @te: pointer to CPUTLBEntry
+ */
+static inline bool tlb_entry_is_empty(const CPUTLBEntry *te)
+{
+ return te->addr_read == -1 && te->addr_write == -1 && te->addr_code == -1;
+}
+
/* Called with tlb_c.lock held */
-static inline void tlb_flush_entry_locked(CPUTLBEntry *tlb_entry,
+static inline bool tlb_flush_entry_locked(CPUTLBEntry *tlb_entry,
target_ulong page)
{
if (tlb_hit_page_anyprot(tlb_entry, page)) {
memset(tlb_entry, -1, sizeof(*tlb_entry));
+ return true;
}
+ return false;
}
/* Called with tlb_c.lock held */
assert_cpu_is_self(ENV_GET_CPU(env));
for (k = 0; k < CPU_VTLB_SIZE; k++) {
- tlb_flush_entry_locked(&env->tlb_v_table[mmu_idx][k], page);
+ if (tlb_flush_entry_locked(&env->tlb_v_table[mmu_idx][k], page)) {
+ tlb_n_used_entries_dec(env, mmu_idx);
+ }
}
}
midx, lp_addr, lp_mask);
tlb_flush_one_mmuidx_locked(env, midx);
} else {
- tlb_flush_entry_locked(tlb_entry(env, midx, page), page);
+ if (tlb_flush_entry_locked(tlb_entry(env, midx, page), page)) {
+ tlb_n_used_entries_dec(env, midx);
+ }
tlb_flush_vtlb_page_locked(env, midx, page);
}
}
qemu_spin_lock(&env->tlb_c.lock);
for (mmu_idx = 0; mmu_idx < NB_MMU_MODES; mmu_idx++) {
unsigned int i;
+ unsigned int n = tlb_n_entries(env, mmu_idx);
- for (i = 0; i < CPU_TLB_SIZE; i++) {
+ for (i = 0; i < n; i++) {
tlb_reset_dirty_range_locked(&env->tlb_table[mmu_idx][i], start1,
length);
}
* Only evict the old entry to the victim tlb if it's for a
* different page; otherwise just overwrite the stale data.
*/
- if (!tlb_hit_page_anyprot(te, vaddr_page)) {
+ if (!tlb_hit_page_anyprot(te, vaddr_page) && !tlb_entry_is_empty(te)) {
unsigned vidx = env->tlb_d[mmu_idx].vindex++ % CPU_VTLB_SIZE;
CPUTLBEntry *tv = &env->tlb_v_table[mmu_idx][vidx];
/* Evict the old entry into the victim tlb. */
copy_tlb_helper_locked(tv, te);
env->iotlb_v[mmu_idx][vidx] = env->iotlb[mmu_idx][index];
+ tlb_n_used_entries_dec(env, mmu_idx);
}
/* refill the tlb */
}
copy_tlb_helper_locked(te, &tn);
+ tlb_n_used_entries_inc(env, mmu_idx);
qemu_spin_unlock(&env->tlb_c.lock);
}
return ram_addr;
}
+/*
+ * Note: tlb_fill() can trigger a resize of the TLB. This means that all of the
+ * caller's prior references to the TLB table (e.g. CPUTLBEntry pointers) must
+ * be discarded and looked up again (e.g. via tlb_entry()).
+ */
+static void tlb_fill(CPUState *cpu, target_ulong addr, int size,
+ MMUAccessType access_type, int mmu_idx, uintptr_t retaddr)
+{
+ CPUClass *cc = CPU_GET_CLASS(cpu);
+ bool ok;
+
+ /*
+ * This is not a probe, so only valid return is success; failure
+ * should result in exception + longjmp to the cpu loop.
+ */
+ ok = cc->tlb_fill(cpu, addr, size, access_type, mmu_idx, false, retaddr);
+ assert(ok);
+}
+
static uint64_t io_readx(CPUArchState *env, CPUIOTLBEntry *iotlbentry,
int mmu_idx,
target_ulong addr, uintptr_t retaddr,
CPUTLBEntry *entry;
target_ulong tlb_addr;
- tlb_fill(cpu, addr, size, MMU_DATA_LOAD, mmu_idx, retaddr);
+ tlb_fill(cpu, addr, size, access_type, mmu_idx, retaddr);
entry = tlb_entry(env, mmu_idx, addr);
- tlb_addr = entry->addr_read;
+ tlb_addr = (access_type == MMU_DATA_LOAD ?
+ entry->addr_read : entry->addr_code);
if (!(tlb_addr & ~(TARGET_PAGE_MASK | TLB_RECHECK))) {
/* RAM access */
uintptr_t haddr = addr + entry->addend;
}
}
+static inline target_ulong tlb_read_ofs(CPUTLBEntry *entry, size_t ofs)
+{
+#if TCG_OVERSIZED_GUEST
+ return *(target_ulong *)((uintptr_t)entry + ofs);
+#else
+ /* ofs might correspond to .addr_write, so use atomic_read */
+ return atomic_read((target_ulong *)((uintptr_t)entry + ofs));
+#endif
+}
+
/* Return true if ADDR is present in the victim tlb, and has been copied
back to the main tlb. */
static bool victim_tlb_hit(CPUArchState *env, size_t mmu_idx, size_t index,
assert_cpu_is_self(ENV_GET_CPU(env));
for (vidx = 0; vidx < CPU_VTLB_SIZE; ++vidx) {
CPUTLBEntry *vtlb = &env->tlb_v_table[mmu_idx][vidx];
- target_ulong cmp;
-
- /* elt_ofs might correspond to .addr_write, so use atomic_read */
-#if TCG_OVERSIZED_GUEST
- cmp = *(target_ulong *)((uintptr_t)vtlb + elt_ofs);
-#else
- cmp = atomic_read((target_ulong *)((uintptr_t)vtlb + elt_ofs));
-#endif
+ target_ulong cmp = tlb_read_ofs(vtlb, elt_ofs);
if (cmp == page) {
/* Found entry in victim tlb, swap tlb and iotlb. */
if (unlikely(!tlb_hit(entry->addr_code, addr))) {
if (!VICTIM_TLB_HIT(addr_code, addr)) {
tlb_fill(ENV_GET_CPU(env), addr, 0, MMU_INST_FETCH, mmu_idx, 0);
+ index = tlb_index(env, mmu_idx, addr);
+ entry = tlb_entry(env, mmu_idx, addr);
}
assert(tlb_hit(entry->addr_code, addr));
}
}
}
+void *tlb_vaddr_to_host(CPUArchState *env, abi_ptr addr,
+ MMUAccessType access_type, int mmu_idx)
+{
+ CPUTLBEntry *entry = tlb_entry(env, mmu_idx, addr);
+ uintptr_t tlb_addr, page;
+ size_t elt_ofs;
+
+ switch (access_type) {
+ case MMU_DATA_LOAD:
+ elt_ofs = offsetof(CPUTLBEntry, addr_read);
+ break;
+ case MMU_DATA_STORE:
+ elt_ofs = offsetof(CPUTLBEntry, addr_write);
+ break;
+ case MMU_INST_FETCH:
+ elt_ofs = offsetof(CPUTLBEntry, addr_code);
+ break;
+ default:
+ g_assert_not_reached();
+ }
+
+ page = addr & TARGET_PAGE_MASK;
+ tlb_addr = tlb_read_ofs(entry, elt_ofs);
+
+ if (!tlb_hit_page(tlb_addr, page)) {
+ uintptr_t index = tlb_index(env, mmu_idx, addr);
+
+ if (!victim_tlb_hit(env, mmu_idx, index, elt_ofs, page)) {
+ CPUState *cs = ENV_GET_CPU(env);
+ CPUClass *cc = CPU_GET_CLASS(cs);
+
+ if (!cc->tlb_fill(cs, addr, 0, access_type, mmu_idx, true, 0)) {
+ /* Non-faulting page table read failed. */
+ return NULL;
+ }
+
+ /* TLB resize via tlb_fill may have moved the entry. */
+ entry = tlb_entry(env, mmu_idx, addr);
+ }
+ tlb_addr = tlb_read_ofs(entry, elt_ofs);
+ }
+
+ if (tlb_addr & ~TARGET_PAGE_MASK) {
+ /* IO access */
+ return NULL;
+ }
+
+ return (void *)((uintptr_t)addr + entry->addend);
+}
+
/* Probe for a read-modify-write atomic operation. Do not allow unaligned
* operations, or io operations to proceed. Return the host address. */
static void *atomic_mmu_lookup(CPUArchState *env, target_ulong addr,
if (!VICTIM_TLB_HIT(addr_write, addr)) {
tlb_fill(ENV_GET_CPU(env), addr, 1 << s_bits, MMU_DATA_STORE,
mmu_idx, retaddr);
+ index = tlb_index(env, mmu_idx, addr);
+ tlbe = tlb_entry(env, mmu_idx, addr);
}
tlb_addr = tlb_addr_write(tlbe) & ~TLB_INVALID_MASK;
}
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