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tcg: Prepare TB invalidation for lockless TB lookup 

When invalidating a translation block, set an invalid flag into the
TranslationBlock structure first.  It is also necessary to check whether
the target TB is still valid after acquiring 'tb_lock' but before calling
tb_add_jump() since TB lookup is to be performed out of 'tb_lock' in
future. Note that we don't have to check 'last_tb'; an already invalidated
TB will not be executed anyway and it is thus safe to patch it.

Suggested-by: Sergey Fedorov <serge.fdrv@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Paolo Bonzini 2016-07-19 08:36:18 +02:00
parent 118b07308a
commit 6d21e4208f
3 changed files with 8 additions and 2 deletions
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5
cpu-exec.c
View File

@ -241,7 +241,8 @@ static bool tb_cmp(const void *p, const void *d)
if (tb->pc == desc->pc &&
tb->page_addr[0] == desc->phys_page1 &&
tb->cs_base == desc->cs_base &&
tb->flags == desc->flags) {
tb->flags == desc->flags &&
!atomic_read(&tb->invalid)) {
/* check next page if needed */
if (tb->page_addr[1] == -1) {
return true;
@ -352,7 +353,7 @@ static inline TranslationBlock *tb_find_fast(CPUState *cpu,
/* Check if translation buffer has been flushed */
if (cpu->tb_flushed) {
cpu->tb_flushed = false;
} else {
} else if (!tb->invalid) {
tb_add_jump(last_tb, tb_exit, tb);
}
}

2
include/exec/exec-all.h
View File

@ -225,6 +225,8 @@ struct TranslationBlock {
#define CF_USE_ICOUNT 0x20000
#define CF_IGNORE_ICOUNT 0x40000 /* Do not generate icount code */
uint16_t invalid;
void *tc_ptr; /* pointer to the translated code */
uint8_t *tc_search; /* pointer to search data */
/* original tb when cflags has CF_NOCACHE */

3
translate-all.c
View File

@ -773,6 +773,7 @@ static TranslationBlock *tb_alloc(target_ulong pc)
tb = &tcg_ctx.tb_ctx.tbs[tcg_ctx.tb_ctx.nb_tbs++];
tb->pc = pc;
tb->cflags = 0;
tb->invalid = false;
return tb;
}
@ -994,6 +995,8 @@ void tb_phys_invalidate(TranslationBlock *tb, tb_page_addr_t page_addr)
uint32_t h;
tb_page_addr_t phys_pc;
atomic_set(&tb->invalid, true);
/* remove the TB from the hash list */
phys_pc = tb->page_addr[0] + (tb->pc & ~TARGET_PAGE_MASK);
h = tb_hash_func(phys_pc, tb->pc, tb->flags);