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-rw-r--r--tcg/region.c891
1 files changed, 891 insertions, 0 deletions
diff --git a/tcg/region.c b/tcg/region.c
new file mode 100644
index 000000000..9cc30d492
--- /dev/null
+++ b/tcg/region.c
@@ -0,0 +1,891 @@
+/*
+ * Memory region management for Tiny Code Generator for QEMU
+ *
+ * Copyright (c) 2008 Fabrice Bellard
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#include "qemu/osdep.h"
+#include "qemu/units.h"
+#include "qapi/error.h"
+#include "exec/exec-all.h"
+#include "tcg/tcg.h"
+#include "tcg-internal.h"
+
+
+struct tcg_region_tree {
+ QemuMutex lock;
+ GTree *tree;
+ /* padding to avoid false sharing is computed at run-time */
+};
+
+/*
+ * We divide code_gen_buffer into equally-sized "regions" that TCG threads
+ * dynamically allocate from as demand dictates. Given appropriate region
+ * sizing, this minimizes flushes even when some TCG threads generate a lot
+ * more code than others.
+ */
+struct tcg_region_state {
+ QemuMutex lock;
+
+ /* fields set at init time */
+ void *start_aligned;
+ void *after_prologue;
+ size_t n;
+ size_t size; /* size of one region */
+ size_t stride; /* .size + guard size */
+ size_t total_size; /* size of entire buffer, >= n * stride */
+
+ /* fields protected by the lock */
+ size_t current; /* current region index */
+ size_t agg_size_full; /* aggregate size of full regions */
+};
+
+static struct tcg_region_state region;
+
+/*
+ * This is an array of struct tcg_region_tree's, with padding.
+ * We use void * to simplify the computation of region_trees[i]; each
+ * struct is found every tree_size bytes.
+ */
+static void *region_trees;
+static size_t tree_size;
+
+bool in_code_gen_buffer(const void *p)
+{
+ /*
+ * Much like it is valid to have a pointer to the byte past the
+ * end of an array (so long as you don't dereference it), allow
+ * a pointer to the byte past the end of the code gen buffer.
+ */
+ return (size_t)(p - region.start_aligned) <= region.total_size;
+}
+
+#ifdef CONFIG_DEBUG_TCG
+const void *tcg_splitwx_to_rx(void *rw)
+{
+ /* Pass NULL pointers unchanged. */
+ if (rw) {
+ g_assert(in_code_gen_buffer(rw));
+ rw += tcg_splitwx_diff;
+ }
+ return rw;
+}
+
+void *tcg_splitwx_to_rw(const void *rx)
+{
+ /* Pass NULL pointers unchanged. */
+ if (rx) {
+ rx -= tcg_splitwx_diff;
+ /* Assert that we end with a pointer in the rw region. */
+ g_assert(in_code_gen_buffer(rx));
+ }
+ return (void *)rx;
+}
+#endif /* CONFIG_DEBUG_TCG */
+
+/* compare a pointer @ptr and a tb_tc @s */
+static int ptr_cmp_tb_tc(const void *ptr, const struct tb_tc *s)
+{
+ if (ptr >= s->ptr + s->size) {
+ return 1;
+ } else if (ptr < s->ptr) {
+ return -1;
+ }
+ return 0;
+}
+
+static gint tb_tc_cmp(gconstpointer ap, gconstpointer bp, gpointer userdata)
+{
+ const struct tb_tc *a = ap;
+ const struct tb_tc *b = bp;
+
+ /*
+ * When both sizes are set, we know this isn't a lookup.
+ * This is the most likely case: every TB must be inserted; lookups
+ * are a lot less frequent.
+ */
+ if (likely(a->size && b->size)) {
+ if (a->ptr > b->ptr) {
+ return 1;
+ } else if (a->ptr < b->ptr) {
+ return -1;
+ }
+ /* a->ptr == b->ptr should happen only on deletions */
+ g_assert(a->size == b->size);
+ return 0;
+ }
+ /*
+ * All lookups have either .size field set to 0.
+ * From the glib sources we see that @ap is always the lookup key. However
+ * the docs provide no guarantee, so we just mark this case as likely.
+ */
+ if (likely(a->size == 0)) {
+ return ptr_cmp_tb_tc(a->ptr, b);
+ }
+ return ptr_cmp_tb_tc(b->ptr, a);
+}
+
+static void tb_destroy(gpointer value)
+{
+ TranslationBlock *tb = value;
+ qemu_spin_destroy(&tb->jmp_lock);
+}
+
+static void tcg_region_trees_init(void)
+{
+ size_t i;
+
+ tree_size = ROUND_UP(sizeof(struct tcg_region_tree), qemu_dcache_linesize);
+ region_trees = qemu_memalign(qemu_dcache_linesize, region.n * tree_size);
+ for (i = 0; i < region.n; i++) {
+ struct tcg_region_tree *rt = region_trees + i * tree_size;
+
+ qemu_mutex_init(&rt->lock);
+ rt->tree = g_tree_new_full(tb_tc_cmp, NULL, NULL, tb_destroy);
+ }
+}
+
+static struct tcg_region_tree *tc_ptr_to_region_tree(const void *p)
+{
+ size_t region_idx;
+
+ /*
+ * Like tcg_splitwx_to_rw, with no assert. The pc may come from
+ * a signal handler over which the caller has no control.
+ */
+ if (!in_code_gen_buffer(p)) {
+ p -= tcg_splitwx_diff;
+ if (!in_code_gen_buffer(p)) {
+ return NULL;
+ }
+ }
+
+ if (p < region.start_aligned) {
+ region_idx = 0;
+ } else {
+ ptrdiff_t offset = p - region.start_aligned;
+
+ if (offset > region.stride * (region.n - 1)) {
+ region_idx = region.n - 1;
+ } else {
+ region_idx = offset / region.stride;
+ }
+ }
+ return region_trees + region_idx * tree_size;
+}
+
+void tcg_tb_insert(TranslationBlock *tb)
+{
+ struct tcg_region_tree *rt = tc_ptr_to_region_tree(tb->tc.ptr);
+
+ g_assert(rt != NULL);
+ qemu_mutex_lock(&rt->lock);
+ g_tree_insert(rt->tree, &tb->tc, tb);
+ qemu_mutex_unlock(&rt->lock);
+}
+
+void tcg_tb_remove(TranslationBlock *tb)
+{
+ struct tcg_region_tree *rt = tc_ptr_to_region_tree(tb->tc.ptr);
+
+ g_assert(rt != NULL);
+ qemu_mutex_lock(&rt->lock);
+ g_tree_remove(rt->tree, &tb->tc);
+ qemu_mutex_unlock(&rt->lock);
+}
+
+/*
+ * Find the TB 'tb' such that
+ * tb->tc.ptr <= tc_ptr < tb->tc.ptr + tb->tc.size
+ * Return NULL if not found.
+ */
+TranslationBlock *tcg_tb_lookup(uintptr_t tc_ptr)
+{
+ struct tcg_region_tree *rt = tc_ptr_to_region_tree((void *)tc_ptr);
+ TranslationBlock *tb;
+ struct tb_tc s = { .ptr = (void *)tc_ptr };
+
+ if (rt == NULL) {
+ return NULL;
+ }
+
+ qemu_mutex_lock(&rt->lock);
+ tb = g_tree_lookup(rt->tree, &s);
+ qemu_mutex_unlock(&rt->lock);
+ return tb;
+}
+
+static void tcg_region_tree_lock_all(void)
+{
+ size_t i;
+
+ for (i = 0; i < region.n; i++) {
+ struct tcg_region_tree *rt = region_trees + i * tree_size;
+
+ qemu_mutex_lock(&rt->lock);
+ }
+}
+
+static void tcg_region_tree_unlock_all(void)
+{
+ size_t i;
+
+ for (i = 0; i < region.n; i++) {
+ struct tcg_region_tree *rt = region_trees + i * tree_size;
+
+ qemu_mutex_unlock(&rt->lock);
+ }
+}
+
+void tcg_tb_foreach(GTraverseFunc func, gpointer user_data)
+{
+ size_t i;
+
+ tcg_region_tree_lock_all();
+ for (i = 0; i < region.n; i++) {
+ struct tcg_region_tree *rt = region_trees + i * tree_size;
+
+ g_tree_foreach(rt->tree, func, user_data);
+ }
+ tcg_region_tree_unlock_all();
+}
+
+size_t tcg_nb_tbs(void)
+{
+ size_t nb_tbs = 0;
+ size_t i;
+
+ tcg_region_tree_lock_all();
+ for (i = 0; i < region.n; i++) {
+ struct tcg_region_tree *rt = region_trees + i * tree_size;
+
+ nb_tbs += g_tree_nnodes(rt->tree);
+ }
+ tcg_region_tree_unlock_all();
+ return nb_tbs;
+}
+
+static void tcg_region_tree_reset_all(void)
+{
+ size_t i;
+
+ tcg_region_tree_lock_all();
+ for (i = 0; i < region.n; i++) {
+ struct tcg_region_tree *rt = region_trees + i * tree_size;
+
+ /* Increment the refcount first so that destroy acts as a reset */
+ g_tree_ref(rt->tree);
+ g_tree_destroy(rt->tree);
+ }
+ tcg_region_tree_unlock_all();
+}
+
+static void tcg_region_bounds(size_t curr_region, void **pstart, void **pend)
+{
+ void *start, *end;
+
+ start = region.start_aligned + curr_region * region.stride;
+ end = start + region.size;
+
+ if (curr_region == 0) {
+ start = region.after_prologue;
+ }
+ /* The final region may have a few extra pages due to earlier rounding. */
+ if (curr_region == region.n - 1) {
+ end = region.start_aligned + region.total_size;
+ }
+
+ *pstart = start;
+ *pend = end;
+}
+
+static void tcg_region_assign(TCGContext *s, size_t curr_region)
+{
+ void *start, *end;
+
+ tcg_region_bounds(curr_region, &start, &end);
+
+ s->code_gen_buffer = start;
+ s->code_gen_ptr = start;
+ s->code_gen_buffer_size = end - start;
+ s->code_gen_highwater = end - TCG_HIGHWATER;
+}
+
+static bool tcg_region_alloc__locked(TCGContext *s)
+{
+ if (region.current == region.n) {
+ return true;
+ }
+ tcg_region_assign(s, region.current);
+ region.current++;
+ return false;
+}
+
+/*
+ * Request a new region once the one in use has filled up.
+ * Returns true on error.
+ */
+bool tcg_region_alloc(TCGContext *s)
+{
+ bool err;
+ /* read the region size now; alloc__locked will overwrite it on success */
+ size_t size_full = s->code_gen_buffer_size;
+
+ qemu_mutex_lock(&region.lock);
+ err = tcg_region_alloc__locked(s);
+ if (!err) {
+ region.agg_size_full += size_full - TCG_HIGHWATER;
+ }
+ qemu_mutex_unlock(&region.lock);
+ return err;
+}
+
+/*
+ * Perform a context's first region allocation.
+ * This function does _not_ increment region.agg_size_full.
+ */
+static void tcg_region_initial_alloc__locked(TCGContext *s)
+{
+ bool err = tcg_region_alloc__locked(s);
+ g_assert(!err);
+}
+
+void tcg_region_initial_alloc(TCGContext *s)
+{
+ qemu_mutex_lock(&region.lock);
+ tcg_region_initial_alloc__locked(s);
+ qemu_mutex_unlock(&region.lock);
+}
+
+/* Call from a safe-work context */
+void tcg_region_reset_all(void)
+{
+ unsigned int n_ctxs = qatomic_read(&tcg_cur_ctxs);
+ unsigned int i;
+
+ qemu_mutex_lock(&region.lock);
+ region.current = 0;
+ region.agg_size_full = 0;
+
+ for (i = 0; i < n_ctxs; i++) {
+ TCGContext *s = qatomic_read(&tcg_ctxs[i]);
+ tcg_region_initial_alloc__locked(s);
+ }
+ qemu_mutex_unlock(&region.lock);
+
+ tcg_region_tree_reset_all();
+}
+
+static size_t tcg_n_regions(size_t tb_size, unsigned max_cpus)
+{
+#ifdef CONFIG_USER_ONLY
+ return 1;
+#else
+ size_t n_regions;
+
+ /*
+ * It is likely that some vCPUs will translate more code than others,
+ * so we first try to set more regions than max_cpus, with those regions
+ * being of reasonable size. If that's not possible we make do by evenly
+ * dividing the code_gen_buffer among the vCPUs.
+ */
+ /* Use a single region if all we have is one vCPU thread */
+ if (max_cpus == 1 || !qemu_tcg_mttcg_enabled()) {
+ return 1;
+ }
+
+ /*
+ * Try to have more regions than max_cpus, with each region being >= 2 MB.
+ * If we can't, then just allocate one region per vCPU thread.
+ */
+ n_regions = tb_size / (2 * MiB);
+ if (n_regions <= max_cpus) {
+ return max_cpus;
+ }
+ return MIN(n_regions, max_cpus * 8);
+#endif
+}
+
+/*
+ * Minimum size of the code gen buffer. This number is randomly chosen,
+ * but not so small that we can't have a fair number of TB's live.
+ *
+ * Maximum size, MAX_CODE_GEN_BUFFER_SIZE, is defined in tcg-target.h.
+ * Unless otherwise indicated, this is constrained by the range of
+ * direct branches on the host cpu, as used by the TCG implementation
+ * of goto_tb.
+ */
+#define MIN_CODE_GEN_BUFFER_SIZE (1 * MiB)
+
+#if TCG_TARGET_REG_BITS == 32
+#define DEFAULT_CODE_GEN_BUFFER_SIZE_1 (32 * MiB)
+#ifdef CONFIG_USER_ONLY
+/*
+ * For user mode on smaller 32 bit systems we may run into trouble
+ * allocating big chunks of data in the right place. On these systems
+ * we utilise a static code generation buffer directly in the binary.
+ */
+#define USE_STATIC_CODE_GEN_BUFFER
+#endif
+#else /* TCG_TARGET_REG_BITS == 64 */
+#ifdef CONFIG_USER_ONLY
+/*
+ * As user-mode emulation typically means running multiple instances
+ * of the translator don't go too nuts with our default code gen
+ * buffer lest we make things too hard for the OS.
+ */
+#define DEFAULT_CODE_GEN_BUFFER_SIZE_1 (128 * MiB)
+#else
+/*
+ * We expect most system emulation to run one or two guests per host.
+ * Users running large scale system emulation may want to tweak their
+ * runtime setup via the tb-size control on the command line.
+ */
+#define DEFAULT_CODE_GEN_BUFFER_SIZE_1 (1 * GiB)
+#endif
+#endif
+
+#define DEFAULT_CODE_GEN_BUFFER_SIZE \
+ (DEFAULT_CODE_GEN_BUFFER_SIZE_1 < MAX_CODE_GEN_BUFFER_SIZE \
+ ? DEFAULT_CODE_GEN_BUFFER_SIZE_1 : MAX_CODE_GEN_BUFFER_SIZE)
+
+#ifdef USE_STATIC_CODE_GEN_BUFFER
+static uint8_t static_code_gen_buffer[DEFAULT_CODE_GEN_BUFFER_SIZE]
+ __attribute__((aligned(CODE_GEN_ALIGN)));
+
+static int alloc_code_gen_buffer(size_t tb_size, int splitwx, Error **errp)
+{
+ void *buf, *end;
+ size_t size;
+
+ if (splitwx > 0) {
+ error_setg(errp, "jit split-wx not supported");
+ return -1;
+ }
+
+ /* page-align the beginning and end of the buffer */
+ buf = static_code_gen_buffer;
+ end = static_code_gen_buffer + sizeof(static_code_gen_buffer);
+ buf = QEMU_ALIGN_PTR_UP(buf, qemu_real_host_page_size);
+ end = QEMU_ALIGN_PTR_DOWN(end, qemu_real_host_page_size);
+
+ size = end - buf;
+
+ /* Honor a command-line option limiting the size of the buffer. */
+ if (size > tb_size) {
+ size = QEMU_ALIGN_DOWN(tb_size, qemu_real_host_page_size);
+ }
+
+ region.start_aligned = buf;
+ region.total_size = size;
+
+ return PROT_READ | PROT_WRITE;
+}
+#elif defined(_WIN32)
+static int alloc_code_gen_buffer(size_t size, int splitwx, Error **errp)
+{
+ void *buf;
+
+ if (splitwx > 0) {
+ error_setg(errp, "jit split-wx not supported");
+ return -1;
+ }
+
+ buf = VirtualAlloc(NULL, size, MEM_RESERVE | MEM_COMMIT,
+ PAGE_EXECUTE_READWRITE);
+ if (buf == NULL) {
+ error_setg_win32(errp, GetLastError(),
+ "allocate %zu bytes for jit buffer", size);
+ return false;
+ }
+
+ region.start_aligned = buf;
+ region.total_size = size;
+
+ return PAGE_READ | PAGE_WRITE | PAGE_EXEC;
+}
+#else
+static int alloc_code_gen_buffer_anon(size_t size, int prot,
+ int flags, Error **errp)
+{
+ void *buf;
+
+ buf = mmap(NULL, size, prot, flags, -1, 0);
+ if (buf == MAP_FAILED) {
+ error_setg_errno(errp, errno,
+ "allocate %zu bytes for jit buffer", size);
+ return -1;
+ }
+
+ region.start_aligned = buf;
+ region.total_size = size;
+ return prot;
+}
+
+#ifndef CONFIG_TCG_INTERPRETER
+#ifdef CONFIG_POSIX
+#include "qemu/memfd.h"
+
+static bool alloc_code_gen_buffer_splitwx_memfd(size_t size, Error **errp)
+{
+ void *buf_rw = NULL, *buf_rx = MAP_FAILED;
+ int fd = -1;
+
+ buf_rw = qemu_memfd_alloc("tcg-jit", size, 0, &fd, errp);
+ if (buf_rw == NULL) {
+ goto fail;
+ }
+
+ buf_rx = mmap(NULL, size, PROT_READ | PROT_EXEC, MAP_SHARED, fd, 0);
+ if (buf_rx == MAP_FAILED) {
+ goto fail_rx;
+ }
+
+ close(fd);
+ region.start_aligned = buf_rw;
+ region.total_size = size;
+ tcg_splitwx_diff = buf_rx - buf_rw;
+
+ return PROT_READ | PROT_WRITE;
+
+ fail_rx:
+ error_setg_errno(errp, errno, "failed to map shared memory for execute");
+ fail:
+ if (buf_rx != MAP_FAILED) {
+ munmap(buf_rx, size);
+ }
+ if (buf_rw) {
+ munmap(buf_rw, size);
+ }
+ if (fd >= 0) {
+ close(fd);
+ }
+ return -1;
+}
+#endif /* CONFIG_POSIX */
+
+#ifdef CONFIG_DARWIN
+#include <mach/mach.h>
+
+extern kern_return_t mach_vm_remap(vm_map_t target_task,
+ mach_vm_address_t *target_address,
+ mach_vm_size_t size,
+ mach_vm_offset_t mask,
+ int flags,
+ vm_map_t src_task,
+ mach_vm_address_t src_address,
+ boolean_t copy,
+ vm_prot_t *cur_protection,
+ vm_prot_t *max_protection,
+ vm_inherit_t inheritance);
+
+static int alloc_code_gen_buffer_splitwx_vmremap(size_t size, Error **errp)
+{
+ kern_return_t ret;
+ mach_vm_address_t buf_rw, buf_rx;
+ vm_prot_t cur_prot, max_prot;
+
+ /* Map the read-write portion via normal anon memory. */
+ if (!alloc_code_gen_buffer_anon(size, PROT_READ | PROT_WRITE,
+ MAP_PRIVATE | MAP_ANONYMOUS, errp)) {
+ return -1;
+ }
+
+ buf_rw = (mach_vm_address_t)region.start_aligned;
+ buf_rx = 0;
+ ret = mach_vm_remap(mach_task_self(),
+ &buf_rx,
+ size,
+ 0,
+ VM_FLAGS_ANYWHERE,
+ mach_task_self(),
+ buf_rw,
+ false,
+ &cur_prot,
+ &max_prot,
+ VM_INHERIT_NONE);
+ if (ret != KERN_SUCCESS) {
+ /* TODO: Convert "ret" to a human readable error message. */
+ error_setg(errp, "vm_remap for jit splitwx failed");
+ munmap((void *)buf_rw, size);
+ return -1;
+ }
+
+ if (mprotect((void *)buf_rx, size, PROT_READ | PROT_EXEC) != 0) {
+ error_setg_errno(errp, errno, "mprotect for jit splitwx");
+ munmap((void *)buf_rx, size);
+ munmap((void *)buf_rw, size);
+ return -1;
+ }
+
+ tcg_splitwx_diff = buf_rx - buf_rw;
+ return PROT_READ | PROT_WRITE;
+}
+#endif /* CONFIG_DARWIN */
+#endif /* CONFIG_TCG_INTERPRETER */
+
+static int alloc_code_gen_buffer_splitwx(size_t size, Error **errp)
+{
+#ifndef CONFIG_TCG_INTERPRETER
+# ifdef CONFIG_DARWIN
+ return alloc_code_gen_buffer_splitwx_vmremap(size, errp);
+# endif
+# ifdef CONFIG_POSIX
+ return alloc_code_gen_buffer_splitwx_memfd(size, errp);
+# endif
+#endif
+ error_setg(errp, "jit split-wx not supported");
+ return -1;
+}
+
+static int alloc_code_gen_buffer(size_t size, int splitwx, Error **errp)
+{
+ ERRP_GUARD();
+ int prot, flags;
+
+ if (splitwx) {
+ prot = alloc_code_gen_buffer_splitwx(size, errp);
+ if (prot >= 0) {
+ return prot;
+ }
+ /*
+ * If splitwx force-on (1), fail;
+ * if splitwx default-on (-1), fall through to splitwx off.
+ */
+ if (splitwx > 0) {
+ return -1;
+ }
+ error_free_or_abort(errp);
+ }
+
+ /*
+ * macOS 11.2 has a bug (Apple Feedback FB8994773) in which mprotect
+ * rejects a permission change from RWX -> NONE when reserving the
+ * guard pages later. We can go the other way with the same number
+ * of syscalls, so always begin with PROT_NONE.
+ */
+ prot = PROT_NONE;
+ flags = MAP_PRIVATE | MAP_ANONYMOUS;
+#ifdef CONFIG_DARWIN
+ /* Applicable to both iOS and macOS (Apple Silicon). */
+ if (!splitwx) {
+ flags |= MAP_JIT;
+ }
+#endif
+
+ return alloc_code_gen_buffer_anon(size, prot, flags, errp);
+}
+#endif /* USE_STATIC_CODE_GEN_BUFFER, WIN32, POSIX */
+
+/*
+ * Initializes region partitioning.
+ *
+ * Called at init time from the parent thread (i.e. the one calling
+ * tcg_context_init), after the target's TCG globals have been set.
+ *
+ * Region partitioning works by splitting code_gen_buffer into separate regions,
+ * and then assigning regions to TCG threads so that the threads can translate
+ * code in parallel without synchronization.
+ *
+ * In softmmu the number of TCG threads is bounded by max_cpus, so we use at
+ * least max_cpus regions in MTTCG. In !MTTCG we use a single region.
+ * Note that the TCG options from the command-line (i.e. -accel accel=tcg,[...])
+ * must have been parsed before calling this function, since it calls
+ * qemu_tcg_mttcg_enabled().
+ *
+ * In user-mode we use a single region. Having multiple regions in user-mode
+ * is not supported, because the number of vCPU threads (recall that each thread
+ * spawned by the guest corresponds to a vCPU thread) is only bounded by the
+ * OS, and usually this number is huge (tens of thousands is not uncommon).
+ * Thus, given this large bound on the number of vCPU threads and the fact
+ * that code_gen_buffer is allocated at compile-time, we cannot guarantee
+ * that the availability of at least one region per vCPU thread.
+ *
+ * However, this user-mode limitation is unlikely to be a significant problem
+ * in practice. Multi-threaded guests share most if not all of their translated
+ * code, which makes parallel code generation less appealing than in softmmu.
+ */
+void tcg_region_init(size_t tb_size, int splitwx, unsigned max_cpus)
+{
+ const size_t page_size = qemu_real_host_page_size;
+ size_t region_size;
+ int have_prot, need_prot;
+
+ /* Size the buffer. */
+ if (tb_size == 0) {
+ size_t phys_mem = qemu_get_host_physmem();
+ if (phys_mem == 0) {
+ tb_size = DEFAULT_CODE_GEN_BUFFER_SIZE;
+ } else {
+ tb_size = QEMU_ALIGN_DOWN(phys_mem / 8, page_size);
+ tb_size = MIN(DEFAULT_CODE_GEN_BUFFER_SIZE, tb_size);
+ }
+ }
+ if (tb_size < MIN_CODE_GEN_BUFFER_SIZE) {
+ tb_size = MIN_CODE_GEN_BUFFER_SIZE;
+ }
+ if (tb_size > MAX_CODE_GEN_BUFFER_SIZE) {
+ tb_size = MAX_CODE_GEN_BUFFER_SIZE;
+ }
+
+ have_prot = alloc_code_gen_buffer(tb_size, splitwx, &error_fatal);
+ assert(have_prot >= 0);
+
+ /* Request large pages for the buffer and the splitwx. */
+ qemu_madvise(region.start_aligned, region.total_size, QEMU_MADV_HUGEPAGE);
+ if (tcg_splitwx_diff) {
+ qemu_madvise(region.start_aligned + tcg_splitwx_diff,
+ region.total_size, QEMU_MADV_HUGEPAGE);
+ }
+
+ /*
+ * Make region_size a multiple of page_size, using aligned as the start.
+ * As a result of this we might end up with a few extra pages at the end of
+ * the buffer; we will assign those to the last region.
+ */
+ region.n = tcg_n_regions(tb_size, max_cpus);
+ region_size = tb_size / region.n;
+ region_size = QEMU_ALIGN_DOWN(region_size, page_size);
+
+ /* A region must have at least 2 pages; one code, one guard */
+ g_assert(region_size >= 2 * page_size);
+ region.stride = region_size;
+
+ /* Reserve space for guard pages. */
+ region.size = region_size - page_size;
+ region.total_size -= page_size;
+
+ /*
+ * The first region will be smaller than the others, via the prologue,
+ * which has yet to be allocated. For now, the first region begins at
+ * the page boundary.
+ */
+ region.after_prologue = region.start_aligned;
+
+ /* init the region struct */
+ qemu_mutex_init(&region.lock);
+
+ /*
+ * Set guard pages in the rw buffer, as that's the one into which
+ * buffer overruns could occur. Do not set guard pages in the rx
+ * buffer -- let that one use hugepages throughout.
+ * Work with the page protections set up with the initial mapping.
+ */
+ need_prot = PAGE_READ | PAGE_WRITE;
+#ifndef CONFIG_TCG_INTERPRETER
+ if (tcg_splitwx_diff == 0) {
+ need_prot |= PAGE_EXEC;
+ }
+#endif
+ for (size_t i = 0, n = region.n; i < n; i++) {
+ void *start, *end;
+
+ tcg_region_bounds(i, &start, &end);
+ if (have_prot != need_prot) {
+ int rc;
+
+ if (need_prot == (PAGE_READ | PAGE_WRITE | PAGE_EXEC)) {
+ rc = qemu_mprotect_rwx(start, end - start);
+ } else if (need_prot == (PAGE_READ | PAGE_WRITE)) {
+ rc = qemu_mprotect_rw(start, end - start);
+ } else {
+ g_assert_not_reached();
+ }
+ if (rc) {
+ error_setg_errno(&error_fatal, errno,
+ "mprotect of jit buffer");
+ }
+ }
+ if (have_prot != 0) {
+ /* Guard pages are nice for bug detection but are not essential. */
+ (void)qemu_mprotect_none(end, page_size);
+ }
+ }
+
+ tcg_region_trees_init();
+
+ /*
+ * Leave the initial context initialized to the first region.
+ * This will be the context into which we generate the prologue.
+ * It is also the only context for CONFIG_USER_ONLY.
+ */
+ tcg_region_initial_alloc__locked(&tcg_init_ctx);
+}
+
+void tcg_region_prologue_set(TCGContext *s)
+{
+ /* Deduct the prologue from the first region. */
+ g_assert(region.start_aligned == s->code_gen_buffer);
+ region.after_prologue = s->code_ptr;
+
+ /* Recompute boundaries of the first region. */
+ tcg_region_assign(s, 0);
+
+ /* Register the balance of the buffer with gdb. */
+ tcg_register_jit(tcg_splitwx_to_rx(region.after_prologue),
+ region.start_aligned + region.total_size -
+ region.after_prologue);
+}
+
+/*
+ * Returns the size (in bytes) of all translated code (i.e. from all regions)
+ * currently in the cache.
+ * See also: tcg_code_capacity()
+ * Do not confuse with tcg_current_code_size(); that one applies to a single
+ * TCG context.
+ */
+size_t tcg_code_size(void)
+{
+ unsigned int n_ctxs = qatomic_read(&tcg_cur_ctxs);
+ unsigned int i;
+ size_t total;
+
+ qemu_mutex_lock(&region.lock);
+ total = region.agg_size_full;
+ for (i = 0; i < n_ctxs; i++) {
+ const TCGContext *s = qatomic_read(&tcg_ctxs[i]);
+ size_t size;
+
+ size = qatomic_read(&s->code_gen_ptr) - s->code_gen_buffer;
+ g_assert(size <= s->code_gen_buffer_size);
+ total += size;
+ }
+ qemu_mutex_unlock(&region.lock);
+ return total;
+}
+
+/*
+ * Returns the code capacity (in bytes) of the entire cache, i.e. including all
+ * regions.
+ * See also: tcg_code_size()
+ */
+size_t tcg_code_capacity(void)
+{
+ size_t guard_size, capacity;
+
+ /* no need for synchronization; these variables are set at init time */
+ guard_size = region.stride - region.size;
+ capacity = region.total_size;
+ capacity -= (region.n - 1) * guard_size;
+ capacity -= region.n * TCG_HIGHWATER;
+
+ return capacity;
+}