[Qemu-devel] [PATCH 3/4] accel/tcg: Add cluster number to TCG TB hash

[Peter Maydell]

Include the cluster number in the hash we use to look
up TBs. This is important because a TB that is valid
for one cluster at a given physical address and set
of CPU flags is not necessarily valid for another:
the two clusters may have different views of physical
memory, or may have different CPU features (eg FPU
present or absent).

We put the cluster number in the high 8 bits of the
TB cflags. This gives us up to 256 clusters, which should
be enough for anybody. If we ever need more, or need
more bits in cflags for other purposes, we could make
tb_hash_func() take more data (and expand qemu_xxhash7()
to qemu_xxhash8()).

Signed-off-by: Peter Maydell <address@hidden>
---
 include/exec/exec-all.h   | 4 +++-
 accel/tcg/cpu-exec.c      | 4 ++++
 accel/tcg/translate-all.c | 3 +++
 3 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/include/exec/exec-all.h b/include/exec/exec-all.h
index 815e5b1e838..aa7b81aaf01 100644
--- a/include/exec/exec-all.h
+++ b/include/exec/exec-all.h
@@ -351,9 +351,11 @@ struct TranslationBlock {
 #define CF_USE_ICOUNT  0x00020000
 #define CF_INVALID     0x00040000 /* TB is stale. Set with @jmp_lock held */
 #define CF_PARALLEL    0x00080000 /* Generate code for a parallel context */
+#define CF_CLUSTER_MASK 0xff000000 /* Top 8 bits are cluster ID */
+#define CF_CLUSTER_SHIFT 24
 /* cflags' mask for hashing/comparison */
 #define CF_HASH_MASK   \
-    (CF_COUNT_MASK | CF_LAST_IO | CF_USE_ICOUNT | CF_PARALLEL)
+    (CF_COUNT_MASK | CF_LAST_IO | CF_USE_ICOUNT | CF_PARALLEL | 
CF_CLUSTER_MASK)
 
     /* Per-vCPU dynamic tracing state used to generate this TB */
     uint32_t trace_vcpu_dstate;
diff --git a/accel/tcg/cpu-exec.c b/accel/tcg/cpu-exec.c
index 870027d4359..e578a1a3aee 100644
--- a/accel/tcg/cpu-exec.c
+++ b/accel/tcg/cpu-exec.c
@@ -336,6 +336,10 @@ TranslationBlock *tb_htable_lookup(CPUState *cpu, 
target_ulong pc,
         return NULL;
     }
     desc.phys_page1 = phys_pc & TARGET_PAGE_MASK;
+
+    cf_mask &= ~CF_CLUSTER_MASK;
+    cf_mask |= cpu->cluster_index << CF_CLUSTER_SHIFT;
+
     h = tb_hash_func(phys_pc, pc, flags, cf_mask, *cpu->trace_dstate);
     return qht_lookup_custom(&tb_ctx.htable, &desc, h, tb_lookup_cmp);
 }
diff --git a/accel/tcg/translate-all.c b/accel/tcg/translate-all.c
index 639f0b27287..ba27f5acc8c 100644
--- a/accel/tcg/translate-all.c
+++ b/accel/tcg/translate-all.c
@@ -1692,6 +1692,9 @@ TranslationBlock *tb_gen_code(CPUState *cpu,
         cflags |= CF_NOCACHE | 1;
     }
 
+    cflags &= ~CF_CLUSTER_MASK;
+    cflags |= cpu->cluster_index << CF_CLUSTER_SHIFT;
+
  buffer_overflow:
     tb = tb_alloc(pc);
     if (unlikely(!tb)) {
-- 
2.19.2