We had done this for user-mode by invoking page_protect
within the translator loop. Extend this to handle system
mode as well. Move page locking out of tb_link_page.
Reported-by: Liren Wei <lr...@bupt.edu.cn>
Reported-by: Richard W.M. Jones <rjo...@redhat.com>
Signed-off-by: Richard Henderson <richard.hender...@linaro.org>
Tested-by: Richard W.M. Jones <rjo...@redhat.com>
---
accel/tcg/internal.h | 30 ++++-
accel/tcg/cpu-exec.c | 20 ++++
accel/tcg/tb-maint.c | 242 ++++++++++++++++++++------------------
accel/tcg/translate-all.c | 43 ++++++-
accel/tcg/translator.c | 34 ++++--
5 files changed, 236 insertions(+), 133 deletions(-)
diff --git a/accel/tcg/internal.h b/accel/tcg/internal.h
index 650c3ac53f..e8cbbde581 100644
--- a/accel/tcg/internal.h
+++ b/accel/tcg/internal.h
@@ -10,6 +10,7 @@
#define ACCEL_TCG_INTERNAL_H
#include "exec/exec-all.h"
+#include "exec/translate-all.h"
/*
* Access to the various translations structures need to be serialised
@@ -35,6 +36,32 @@ static inline void page_table_config_init(void) { }
void page_table_config_init(void);
#endif
+#ifdef CONFIG_USER_ONLY
+/*
+ * For user-only, page_protect sets the page read-only.
+ * Since most execution is already on read-only pages, and we'd need to
+ * account for other TBs on the same page, defer undoing any page protection
+ * until we receive the write fault.
+ */
+static inline void tb_lock_page0(tb_page_addr_t p0)
+{
+ page_protect(p0);
+}
+
+static inline void tb_lock_page1(tb_page_addr_t p0, tb_page_addr_t p1)
+{
+ page_protect(p1);
+}
+
+static inline void tb_unlock_page1(tb_page_addr_t p0, tb_page_addr_t p1) { }
+static inline void tb_unlock_pages(TranslationBlock *tb) { }
+#else
+void tb_lock_page0(tb_page_addr_t);
+void tb_lock_page1(tb_page_addr_t, tb_page_addr_t);
+void tb_unlock_page1(tb_page_addr_t, tb_page_addr_t);
+void tb_unlock_pages(TranslationBlock *);
+#endif
+
#ifdef CONFIG_SOFTMMU
void tb_invalidate_phys_range_fast(ram_addr_t ram_addr,
unsigned size,
@@ -48,8 +75,7 @@ TranslationBlock *tb_gen_code(CPUState *cpu, vaddr pc,
void page_init(void);
void tb_htable_init(void);
void tb_reset_jump(TranslationBlock *tb, int n);
-TranslationBlock *tb_link_page(TranslationBlock *tb, tb_page_addr_t phys_pc,
- tb_page_addr_t phys_page2);
+TranslationBlock *tb_link_page(TranslationBlock *tb);
bool tb_invalidate_phys_page_unwind(tb_page_addr_t addr, uintptr_t pc);
void cpu_restore_state_from_tb(CPUState *cpu, TranslationBlock *tb,
uintptr_t host_pc);
diff --git a/accel/tcg/cpu-exec.c b/accel/tcg/cpu-exec.c
index 31aa320513..fdd6d3e0e4 100644
--- a/accel/tcg/cpu-exec.c
+++ b/accel/tcg/cpu-exec.c
@@ -536,6 +536,26 @@ static void cpu_exec_longjmp_cleanup(CPUState *cpu)
if (have_mmap_lock()) {
mmap_unlock();
}
+#else
+ /*
+ * For softmmu, a tlb_fill fault during translation will land here,
+ * and we need to release any page locks held. In system mode we
+ * have one tcg_ctx per thread, so we know it was this cpu doing
+ * the translation.
+ *
+ * Alternative 1: Install a cleanup to be called via an exception
+ * handling safe longjmp. It seems plausible that all our hosts
+ * support such a thing. We'd have to properly register unwind info
+ * for the JIT for EH, rather that just for GDB.
+ *
+ * Alternative 2: Set and restore cpu->jmp_env in tb_gen_code to
+ * capture the cpu_loop_exit longjmp, perform the cleanup, and
+ * jump again to arrive here.
+ */
+ if (tcg_ctx->gen_tb) {
+ tb_unlock_pages(tcg_ctx->gen_tb);
+ tcg_ctx->gen_tb = NULL;
+ }
#endif
if (qemu_mutex_iothread_locked()) {
qemu_mutex_unlock_iothread();
diff --git a/accel/tcg/tb-maint.c b/accel/tcg/tb-maint.c
index 9566224d18..c406b2f7b7 100644
--- a/accel/tcg/tb-maint.c
+++ b/accel/tcg/tb-maint.c
@@ -70,17 +70,7 @@ typedef struct PageDesc PageDesc;
*/
#define assert_page_locked(pd) tcg_debug_assert(have_mmap_lock())
-static inline void page_lock_pair(PageDesc **ret_p1, tb_page_addr_t phys1,
- PageDesc **ret_p2, tb_page_addr_t phys2,
- bool alloc)
-{
- *ret_p1 = NULL;
- *ret_p2 = NULL;
-}
-
-static inline void page_unlock(PageDesc *pd) { }
-static inline void page_lock_tb(const TranslationBlock *tb) { }
-static inline void page_unlock_tb(const TranslationBlock *tb) { }
+static inline void tb_lock_pages(const TranslationBlock *tb) { }
/*
* For user-only, since we are protecting all of memory with a single lock,
@@ -96,7 +86,7 @@ static void tb_remove_all(void)
}
/* Call with mmap_lock held. */
-static void tb_record(TranslationBlock *tb, PageDesc *p1, PageDesc *p2)
+static void tb_record(TranslationBlock *tb)
{
vaddr addr;
int flags;
@@ -391,12 +381,108 @@ static void page_lock(PageDesc *pd)
qemu_spin_lock(&pd->lock);
}
+/* Like qemu_spin_trylock, returns false on success */
+static bool page_trylock(PageDesc *pd)
+{
+ bool busy = qemu_spin_trylock(&pd->lock);
+ if (!busy) {
+ page_lock__debug(pd);
+ }
+ return busy;
+}
+
static void page_unlock(PageDesc *pd)
{
qemu_spin_unlock(&pd->lock);
page_unlock__debug(pd);
}
+void tb_lock_page0(tb_page_addr_t paddr)
+{
+ page_lock(page_find_alloc(paddr >> TARGET_PAGE_BITS, true));
+}
+
+void tb_lock_page1(tb_page_addr_t paddr0, tb_page_addr_t paddr1)
+{
+ tb_page_addr_t pindex0 = paddr0 >> TARGET_PAGE_BITS;
+ tb_page_addr_t pindex1 = paddr1 >> TARGET_PAGE_BITS;
+ PageDesc *pd0, *pd1;
+
+ if (pindex0 == pindex1) {
+ /* Identical pages, and the first page is already locked. */
+ return;
+ }
+
+ pd1 = page_find_alloc(pindex1, true);
+ if (pindex0 < pindex1) {
+ /* Correct locking order, we may block. */
+ page_lock(pd1);
+ return;
+ }
+
+ /* Incorrect locking order, we cannot block lest we deadlock. */
+ if (!page_trylock(pd1)) {
+ return;
+ }
+
+ /*
+ * Drop the lock on page0 and get both page locks in the right order.
+ * Restart translation via longjmp.
+ */
+ pd0 = page_find_alloc(pindex0, false);
+ page_unlock(pd0);
+ page_lock(pd1);
+ page_lock(pd0);
+ siglongjmp(tcg_ctx->jmp_trans, -3);
+}
+
+void tb_unlock_page1(tb_page_addr_t paddr0, tb_page_addr_t paddr1)
+{
+ tb_page_addr_t pindex0 = paddr0 >> TARGET_PAGE_BITS;
+ tb_page_addr_t pindex1 = paddr1 >> TARGET_PAGE_BITS;
+
+ if (pindex0 != pindex1) {
+ page_unlock(page_find_alloc(pindex1, false));
+ }
+}
+
+static void tb_lock_pages(TranslationBlock *tb)
+{
+ tb_page_addr_t paddr0 = tb_page_addr0(tb);
+ tb_page_addr_t paddr1 = tb_page_addr1(tb);
+ tb_page_addr_t pindex0 = paddr0 >> TARGET_PAGE_BITS;
+ tb_page_addr_t pindex1 = paddr1 >> TARGET_PAGE_BITS;
+
+ if (unlikely(paddr0 == -1)) {
+ return;
+ }
+ if (unlikely(paddr1 != -1) && pindex0 != pindex1) {
+ if (pindex0 < pindex1) {
+ page_lock(page_find_alloc(pindex0, true));
+ page_lock(page_find_alloc(pindex1, true));
+ return;
+ }
+ page_lock(page_find_alloc(pindex1, true));
+ }
+ page_lock(page_find_alloc(pindex0, true));
+}
+
+void tb_unlock_pages(TranslationBlock *tb)
+{
+ tb_page_addr_t paddr0 = tb_page_addr0(tb);
+ tb_page_addr_t paddr1 = tb_page_addr1(tb);
+ tb_page_addr_t pindex0 = paddr0 >> TARGET_PAGE_BITS;
+ tb_page_addr_t pindex1 = paddr1 >> TARGET_PAGE_BITS;
+
+ if (unlikely(paddr0 == -1)) {
+ return;
+ }
+ if (unlikely(paddr1 != -1) && pindex0 != pindex1) {
+ page_unlock(page_find_alloc(pindex1, false));
+ }
+ page_unlock(page_find_alloc(pindex0, false));
+}
+
static inline struct page_entry *
page_entry_new(PageDesc *pd, tb_page_addr_t index)
{
@@ -420,13 +506,10 @@ static void page_entry_destroy(gpointer p)
/* returns false on success */
static bool page_entry_trylock(struct page_entry *pe)
{
- bool busy;
-
- busy = qemu_spin_trylock(&pe->pd->lock);
+ bool busy = page_trylock(pe->pd);
if (!busy) {
g_assert(!pe->locked);
pe->locked = true;
- page_lock__debug(pe->pd);
}
return busy;
}
@@ -604,8 +687,7 @@ static void tb_remove_all(void)
* Add the tb in the target page and protect it if necessary.
* Called with @p->lock held.
*/
-static inline void tb_page_add(PageDesc *p, TranslationBlock *tb,
- unsigned int n)
+static void tb_page_add(PageDesc *p, TranslationBlock *tb, unsigned int n)
{
bool page_already_protected;
@@ -625,15 +707,21 @@ static inline void tb_page_add(PageDesc *p,
TranslationBlock *tb,
}
}
-static void tb_record(TranslationBlock *tb, PageDesc *p1, PageDesc *p2)
+static void tb_record(TranslationBlock *tb)
{
- tb_page_add(p1, tb, 0);
- if (unlikely(p2)) {
- tb_page_add(p2, tb, 1);
+ tb_page_addr_t paddr0 = tb_page_addr0(tb);
+ tb_page_addr_t paddr1 = tb_page_addr1(tb);
+ tb_page_addr_t pindex0 = paddr0 >> TARGET_PAGE_BITS;
+ tb_page_addr_t pindex1 = paddr0 >> TARGET_PAGE_BITS;
+
+ assert(paddr0 != -1);
+ if (unlikely(paddr1 != -1) && pindex0 != pindex1) {
+ tb_page_add(page_find_alloc(pindex1, false), tb, 1);
}
+ tb_page_add(page_find_alloc(pindex0, false), tb, 0);
}
-static inline void tb_page_remove(PageDesc *pd, TranslationBlock *tb)
+static void tb_page_remove(PageDesc *pd, TranslationBlock *tb)
{
TranslationBlock *tb1;
uintptr_t *pprev;
@@ -653,74 +741,16 @@ static inline void tb_page_remove(PageDesc *pd,
TranslationBlock *tb)
static void tb_remove(TranslationBlock *tb)
{
- PageDesc *pd;
+ tb_page_addr_t paddr0 = tb_page_addr0(tb);
+ tb_page_addr_t paddr1 = tb_page_addr1(tb);
+ tb_page_addr_t pindex0 = paddr0 >> TARGET_PAGE_BITS;
+ tb_page_addr_t pindex1 = paddr0 >> TARGET_PAGE_BITS;
- pd = page_find(tb->page_addr[0] >> TARGET_PAGE_BITS);
- tb_page_remove(pd, tb);
- if (unlikely(tb->page_addr[1] != -1)) {
- pd = page_find(tb->page_addr[1] >> TARGET_PAGE_BITS);
- tb_page_remove(pd, tb);
- }
-}
-
-static void page_lock_pair(PageDesc **ret_p1, tb_page_addr_t phys1,
- PageDesc **ret_p2, tb_page_addr_t phys2, bool alloc)
-{
- PageDesc *p1, *p2;
- tb_page_addr_t page1;
- tb_page_addr_t page2;
-
- assert_memory_lock();
- g_assert(phys1 != -1);
-
- page1 = phys1 >> TARGET_PAGE_BITS;
- page2 = phys2 >> TARGET_PAGE_BITS;
-
- p1 = page_find_alloc(page1, alloc);
- if (ret_p1) {
- *ret_p1 = p1;
- }
- if (likely(phys2 == -1)) {
- page_lock(p1);
- return;
- } else if (page1 == page2) {
- page_lock(p1);
- if (ret_p2) {
- *ret_p2 = p1;
- }
- return;
- }
- p2 = page_find_alloc(page2, alloc);
- if (ret_p2) {
- *ret_p2 = p2;
- }
- if (page1 < page2) {
- page_lock(p1);
- page_lock(p2);
- } else {
- page_lock(p2);
- page_lock(p1);
- }
-}
-
-/* lock the page(s) of a TB in the correct acquisition order */
-static void page_lock_tb(const TranslationBlock *tb)
-{
- page_lock_pair(NULL, tb_page_addr0(tb), NULL, tb_page_addr1(tb), false);
-}
-
-static void page_unlock_tb(const TranslationBlock *tb)
-{
- PageDesc *p1 = page_find(tb_page_addr0(tb) >> TARGET_PAGE_BITS);
-
- page_unlock(p1);
- if (unlikely(tb_page_addr1(tb) != -1)) {
- PageDesc *p2 = page_find(tb_page_addr1(tb) >> TARGET_PAGE_BITS);
-
- if (p2 != p1) {
- page_unlock(p2);
- }
+ assert(paddr0 != -1);
+ if (unlikely(paddr1 != -1) && pindex0 != pindex1) {
+ tb_page_remove(page_find_alloc(pindex1, false), tb);
}
+ tb_page_remove(page_find_alloc(pindex0, false), tb);
}
#endif /* CONFIG_USER_ONLY */
@@ -925,18 +955,16 @@ static void tb_phys_invalidate__locked(TranslationBlock
*tb)
void tb_phys_invalidate(TranslationBlock *tb, tb_page_addr_t page_addr)
{
if (page_addr == -1 && tb_page_addr0(tb) != -1) {
- page_lock_tb(tb);
+ tb_lock_pages(tb);
do_tb_phys_invalidate(tb, true);
- page_unlock_tb(tb);
+ tb_unlock_pages(tb);
} else {
do_tb_phys_invalidate(tb, false);
}
}
/*
- * Add a new TB and link it to the physical page tables. phys_page2 is
- * (-1) to indicate that only one page contains the TB.
- *
+ * Add a new TB and link it to the physical page tables.
* Called with mmap_lock held for user-mode emulation.
*
* Returns a pointer @tb, or a pointer to an existing TB that matches @tb.
@@ -944,43 +972,29 @@ void tb_phys_invalidate(TranslationBlock *tb,
tb_page_addr_t page_addr)
* for the same block of guest code that @tb corresponds to. In that case,
* the caller should discard the original @tb, and use instead the returned TB.
*/
-TranslationBlock *tb_link_page(TranslationBlock *tb, tb_page_addr_t phys_pc,
- tb_page_addr_t phys_page2)
+TranslationBlock *tb_link_page(TranslationBlock *tb)
{
- PageDesc *p;
- PageDesc *p2 = NULL;
void *existing_tb = NULL;
uint32_t h;
assert_memory_lock();
tcg_debug_assert(!(tb->cflags & CF_INVALID));
- /*
- * Add the TB to the page list, acquiring first the pages's locks.
- * We keep the locks held until after inserting the TB in the hash table,
- * so that if the insertion fails we know for sure that the TBs are still
- * in the page descriptors.
- * Note that inserting into the hash table first isn't an option, since
- * we can only insert TBs that are fully initialized.
- */
- page_lock_pair(&p, phys_pc, &p2, phys_page2, true);
- tb_record(tb, p, p2);
+ tb_record(tb);
/* add in the hash table */
- h = tb_hash_func(phys_pc, (tb->cflags & CF_PCREL ? 0 : tb->pc),
+ h = tb_hash_func(tb_page_addr0(tb), (tb->cflags & CF_PCREL ? 0 : tb->pc),
tb->flags, tb->cs_base, tb->cflags);
qht_insert(&tb_ctx.htable, tb, h, &existing_tb);
/* remove TB from the page(s) if we couldn't insert it */
if (unlikely(existing_tb)) {
tb_remove(tb);
- tb = existing_tb;
+ tb_unlock_pages(tb);
+ return existing_tb;
}
- if (p2 && p2 != p) {
- page_unlock(p2);
- }
- page_unlock(p);
+ tb_unlock_pages(tb);
return tb;
}
diff --git a/accel/tcg/translate-all.c b/accel/tcg/translate-all.c
index d3d4fbc1a4..4c17474fa2 100644
--- a/accel/tcg/translate-all.c
+++ b/accel/tcg/translate-all.c
@@ -290,7 +290,7 @@ TranslationBlock *tb_gen_code(CPUState *cpu,
{
CPUArchState *env = cpu->env_ptr;
TranslationBlock *tb, *existing_tb;
- tb_page_addr_t phys_pc;
+ tb_page_addr_t phys_pc, phys_p2;
tcg_insn_unit *gen_code_buf;
int gen_code_size, search_size, max_insns;
int64_t ti;
@@ -313,6 +313,7 @@ TranslationBlock *tb_gen_code(CPUState *cpu,
QEMU_BUILD_BUG_ON(CF_COUNT_MASK + 1 != TCG_MAX_INSNS);
buffer_overflow:
+ assert_no_pages_locked();
tb = tcg_tb_alloc(tcg_ctx);
if (unlikely(!tb)) {
/* flush must be done */
@@ -333,6 +334,10 @@ TranslationBlock *tb_gen_code(CPUState *cpu,
tb->cflags = cflags;
tb_set_page_addr0(tb, phys_pc);
tb_set_page_addr1(tb, -1);
+ if (phys_pc != -1) {
+ tb_lock_page0(phys_pc);
+ }
+
tcg_ctx->gen_tb = tb;
tcg_ctx->addr_type = TARGET_LONG_BITS == 32 ? TCG_TYPE_I32 : TCG_TYPE_I64;
#ifdef CONFIG_SOFTMMU
@@ -349,8 +354,7 @@ TranslationBlock *tb_gen_code(CPUState *cpu,
tcg_ctx->guest_mo = TCG_MO_ALL;
#endif
- tb_overflow:
-
+ restart_translate:
trace_translate_block(tb, pc, tb->tc.ptr);
gen_code_size = setjmp_gen_code(env, tb, pc, host_pc, &max_insns, &ti);
@@ -369,6 +373,7 @@ TranslationBlock *tb_gen_code(CPUState *cpu,
qemu_log_mask(CPU_LOG_TB_OP | CPU_LOG_TB_OP_OPT,
"Restarting code generation for "
"code_gen_buffer overflow\n");
+ tb_unlock_pages(tb);
goto buffer_overflow;
case -2:
@@ -387,14 +392,39 @@ TranslationBlock *tb_gen_code(CPUState *cpu,
"Restarting code generation with "
"smaller translation block (max %d insns)\n",
max_insns);
- goto tb_overflow;
+
+ /*
+ * The half-sized TB may not cross pages.
+ * TODO: Fix all targets that cross pages except with
+ * the first insn, at which point this can't be reached.
+ */
+ phys_p2 = tb_page_addr1(tb);
+ if (unlikely(phys_p2 != -1)) {
+ tb_unlock_page1(phys_pc, phys_p2);
+ tb_set_page_addr1(tb, -1);
+ }
+ goto restart_translate;
+
+ case -3:
+ /*
+ * We had a page lock ordering problem. In order to avoid
+ * deadlock we had to drop the lock on page0, which means
+ * that everything we translated so far is compromised.
+ * Restart with locks held on both pages.
+ */
+ qemu_log_mask(CPU_LOG_TB_OP | CPU_LOG_TB_OP_OPT,
+ "Restarting code generation with re-locked pages");
+ goto restart_translate;
default:
g_assert_not_reached();
}
}
+ tcg_ctx->gen_tb = NULL;
+
search_size = encode_search(tb, (void *)gen_code_buf + gen_code_size);
if (unlikely(search_size < 0)) {
+ tb_unlock_pages(tb);
goto buffer_overflow;
}
tb->tc.size = gen_code_size;
@@ -504,6 +534,7 @@ TranslationBlock *tb_gen_code(CPUState *cpu,
* before attempting to link to other TBs or add to the lookup table.
*/
if (tb_page_addr0(tb) == -1) {
+ assert_no_pages_locked();
return tb;
}
@@ -518,7 +549,9 @@ TranslationBlock *tb_gen_code(CPUState *cpu,
* No explicit memory barrier is required -- tb_link_page() makes the
* TB visible in a consistent state.
*/
- existing_tb = tb_link_page(tb, tb_page_addr0(tb), tb_page_addr1(tb));
+ existing_tb = tb_link_page(tb);
+ assert_no_pages_locked();
+
/* if the TB already exists, discard what we just translated */
if (unlikely(existing_tb != tb)) {
uintptr_t orig_aligned = (uintptr_t)gen_code_buf;
diff --git a/accel/tcg/translator.c b/accel/tcg/translator.c
index 0fd9efceba..1a6a5448c8 100644
--- a/accel/tcg/translator.c
+++ b/accel/tcg/translator.c
@@ -12,9 +12,9 @@
#include "qemu/error-report.h"
#include "exec/exec-all.h"
#include "exec/translator.h"
-#include "exec/translate-all.h"
#include "exec/plugin-gen.h"
#include "tcg/tcg-op-common.h"
+#include "internal.h"
static void gen_io_start(void)
{
@@ -147,10 +147,6 @@ void translator_loop(CPUState *cpu, TranslationBlock *tb,
int *max_insns,
db->host_addr[0] = host_pc;
db->host_addr[1] = NULL;
-#ifdef CONFIG_USER_ONLY
- page_protect(pc);
-#endif
-
ops->init_disas_context(db, cpu);
tcg_debug_assert(db->is_jmp == DISAS_NEXT); /* no early exit */
@@ -256,22 +252,36 @@ static void *translator_access(CPUArchState *env,
DisasContextBase *db,
host = db->host_addr[1];
base = TARGET_PAGE_ALIGN(db->pc_first);
if (host == NULL) {
- tb_page_addr_t phys_page =
- get_page_addr_code_hostp(env, base, &db->host_addr[1]);
+ tb_page_addr_t page0, old_page1, new_page1;
+
+ new_page1 = get_page_addr_code_hostp(env, base, &db->host_addr[1]);
/*
* If the second page is MMIO, treat as if the first page
* was MMIO as well, so that we do not cache the TB.
*/
- if (unlikely(phys_page == -1)) {
+ if (unlikely(new_page1 == -1)) {
+ tb_unlock_pages(tb);
tb_set_page_addr0(tb, -1);
return NULL;
}
- tb_set_page_addr1(tb, phys_page);
-#ifdef CONFIG_USER_ONLY
- page_protect(end);
-#endif
+ /*
+ * If this is not the first time around, and page1 matches,
+ * then we already have the page locked. Alternately, we're
+ * not doing anything to prevent the PTE from changing, so
+ * we might wind up with a different page, requiring us to
+ * re-do the locking.
+ */
+ old_page1 = tb_page_addr1(tb);
+ if (likely(new_page1 != old_page1)) {
+ page0 = tb_page_addr0(tb);
+ if (unlikely(old_page1 != -1)) {
+ tb_unlock_page1(page0, old_page1);
+ }
+ tb_set_page_addr1(tb, new_page1);
+ tb_lock_page1(page0, new_page1);
+ }
host = db->host_addr[1];
}
--
2.34.1
