[PATCH v2 1/3] target/ppc: Fix broadcast tlbie synchronisation

[Nicholas Piggin <npiggin@gmail.com>]

With mttcg, broadcast tlbie instructions do not wait until other vCPUs
have been kicked out of TCG execution before they complete (including
necessary subsequent tlbsync, etc., instructions). This is contrary to
the ISA, and it permits other vCPUs to use translations after the TLB
flush. For example:

   // *memP is initially 0, memV maps to memP with *pte

   CPU0
     *pte = 0;
     ptesync ; tlbie ; eieio ; tlbsync ; ptesync
     *memP = 1;

   CPU1
     assert(*memV == 0);

It is possible for the assertion to fail because CPU1 translates memV
using the TLB after CPU0 has stored 1 to the underlying memory. The
correct behaviour would be no assertion and possibly a page fault due
to pte being cleared.

This race was observed with a careful test case where the CPU1 checks
run in a large TB making multiple loads so it can run for the entire
CPU0 period between clearing the pte and storing the memory, but host
vCPU thread preemption could cause the race to hit anywhere.

As explained in commit 4ddc104689b ("target/ppc: Fix tlbie"), it is not
enough to just use tlb_flush_all_cpus_synced(), because that does not
execute until the calling CPU has finished its TB. It is also required
that the TB is ended, which will guarantee all CPUs have run the work
before the next instruction will be executed.

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
 target/ppc/helper_regs.c                     | 2 +-
 target/ppc/mmu_helper.c                      | 2 +-
 target/ppc/translate.c                       | 7 +++++++
 target/ppc/translate/storage-ctrl-impl.c.inc | 7 +++++++
 4 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/target/ppc/helper_regs.c b/target/ppc/helper_regs.c
index 25258986e3..9094ae5004 100644
--- a/target/ppc/helper_regs.c
+++ b/target/ppc/helper_regs.c
@@ -334,7 +334,7 @@ void check_tlb_flush(CPUPPCState *env, bool global)
     if (global && (env->tlb_need_flush & TLB_NEED_GLOBAL_FLUSH)) {
         env->tlb_need_flush &= ~TLB_NEED_GLOBAL_FLUSH;
         env->tlb_need_flush &= ~TLB_NEED_LOCAL_FLUSH;
-        tlb_flush_all_cpus(cs);
+        tlb_flush_all_cpus_synced(cs);
         return;
     }
 
diff --git a/target/ppc/mmu_helper.c b/target/ppc/mmu_helper.c
index c071b4d5e2..aaa5bfc62a 100644
--- a/target/ppc/mmu_helper.c
+++ b/target/ppc/mmu_helper.c
@@ -533,7 +533,7 @@ void helper_tlbie_isa300(CPUPPCState *env, target_ulong rb, target_ulong rs,
     if (local) {
         tlb_flush_page(env_cpu(env), addr);
     } else {
-        tlb_flush_page_all_cpus(env_cpu(env), addr);
+        tlb_flush_page_all_cpus_synced(env_cpu(env), addr);
     }
     return;
 
diff --git a/target/ppc/translate.c b/target/ppc/translate.c
index 93ffec787c..4ac8af2058 100644
--- a/target/ppc/translate.c
+++ b/target/ppc/translate.c
@@ -3495,6 +3495,13 @@ static inline void gen_check_tlb_flush(DisasContext *ctx, bool global)
         gen_helper_check_tlb_flush_local(tcg_env);
     }
     gen_set_label(l);
+    if (global) {
+        /*
+         * Global TLB flush uses async-work which must run before the
+         * next instruction, so this must be the last in the TB.
+         */
+        ctx->base.is_jmp = DISAS_EXIT_UPDATE;
+    }
 }
 #else
 static inline void gen_check_tlb_flush(DisasContext *ctx, bool global) { }
diff --git a/target/ppc/translate/storage-ctrl-impl.c.inc b/target/ppc/translate/storage-ctrl-impl.c.inc
index 74c23a4191..b8b4454663 100644
--- a/target/ppc/translate/storage-ctrl-impl.c.inc
+++ b/target/ppc/translate/storage-ctrl-impl.c.inc
@@ -224,6 +224,13 @@ static bool do_tlbie(DisasContext *ctx, arg_X_tlbie *a, bool local)
                                  a->prs << TLBIE_F_PRS_SHIFT |
                                  a->r << TLBIE_F_R_SHIFT |
                                  local << TLBIE_F_LOCAL_SHIFT));
+        if (!local) {
+            /*
+             * Global TLB flush uses async-work which must run before the
+             * next instruction, so this must be the last in the TB.
+             */
+            ctx->base.is_jmp = DISAS_EXIT_UPDATE;
+        }
         return true;
 #endif
 
-- 
2.43.0