target/ppc: Fix CPU reservation migration for record-replay

ppc only migrates reserve_addr, so the destination machine can get a
valid reservation with an incorrect reservation value of 0. Prior to
commit 392d328abe753 ("target/ppc: Ensure stcx size matches larx"),
this could permit a stcx. to incorrectly succeed. That commit
inadvertently fixed that bug because the target machine starts with an
impossible reservation size of 0, so any stcx. will fail.

This behaviour is permitted by the ISA because reservation loss may
have implementation-dependent cause. What's more, with KVM machines it
is impossible save or reasonably restore reservation state. However if
the vmstate is being used for record-replay, the reservation must be
saved and restored exactly in order for execution from snapshot to
match the record.

This patch deprecates the existing incomplete reserve_addr vmstate,
and adds a new vmstate subsection with complete reservation state.
The new vmstate is needed only when record-replay mode is active.

Acked-by: Pavel Dovgalyuk <Pavel.Dovgalyuk@ispras.ru>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Cédric Le Goater <clg@kaod.org>

diff --git a/target/ppc/cpu.h b/target/ppc/cpu.h
index 7e7a60f68f793292bb7d8d9f25b41ac3812bbf5a..77113521acfd5a025ccab42440276471d29cf857 100644 (file)
--- a/target/ppc/cpu.h
+++ b/target/ppc/cpu.h
@@ -1121,7 +1121,9 @@ struct CPUArchState {
     target_ulong reserve_addr;   /* Reservation address */
     target_ulong reserve_length; /* Reservation larx op size (bytes) */
     target_ulong reserve_val;    /* Reservation value */
+#if defined(TARGET_PPC64)
     target_ulong reserve_val2;
+#endif
 
     /* These are used in supervisor mode only */
     target_ulong msr;      /* machine state register */

diff --git a/target/ppc/machine.c b/target/ppc/machine.c
index 3265338e164b7f521873bf2bf96489ee3cb65a91..68cbdffecd4f5042464473a5eb00f2326fab1c84 100644 (file)
--- a/target/ppc/machine.c
+++ b/target/ppc/machine.c
@@ -9,6 +9,7 @@
 #include "qapi/error.h"
 #include "kvm_ppc.h"
 #include "power8-pmu.h"
+#include "sysemu/replay.h"
 
 static void post_load_update_msr(CPUPPCState *env)
 {
@@ -689,6 +690,27 @@ static const VMStateDescription vmstate_compat = {
     }
 };
 
+static bool reservation_needed(void *opaque)
+{
+    return (replay_mode != REPLAY_MODE_NONE);
+}
+
+static const VMStateDescription vmstate_reservation = {
+    .name = "cpu/reservation",
+    .version_id = 1,
+    .minimum_version_id = 1,
+    .needed = reservation_needed,
+    .fields = (VMStateField[]) {
+        VMSTATE_UINTTL(env.reserve_addr, PowerPCCPU),
+        VMSTATE_UINTTL(env.reserve_length, PowerPCCPU),
+        VMSTATE_UINTTL(env.reserve_val, PowerPCCPU),
+#if defined(TARGET_PPC64)
+        VMSTATE_UINTTL(env.reserve_val2, PowerPCCPU),
+#endif
+        VMSTATE_END_OF_LIST()
+    }
+};
+
 const VMStateDescription vmstate_ppc_cpu = {
     .name = "cpu",
     .version_id = 5,
@@ -710,8 +732,7 @@ const VMStateDescription vmstate_ppc_cpu = {
         VMSTATE_UINTTL_ARRAY(env.spr, PowerPCCPU, 1024),
         VMSTATE_UINT64(env.spe_acc, PowerPCCPU),
 
-        /* Reservation */
-        VMSTATE_UINTTL(env.reserve_addr, PowerPCCPU),
+        VMSTATE_UNUSED(sizeof(target_ulong)), /* was env.reserve_addr */
 
         /* Supervisor mode architected state */
         VMSTATE_UINTTL(env.msr, PowerPCCPU),
@@ -740,6 +761,7 @@ const VMStateDescription vmstate_ppc_cpu = {
         &vmstate_tlbemb,
         &vmstate_tlbmas,
         &vmstate_compat,
+        &vmstate_reservation,
         NULL
     }
 };

diff --git a/target/ppc/translate.c b/target/ppc/translate.c
index 16592194e2433d2141e4870f4b0ad7822d672249..6b242ae0a6bbe7525b8671589e61b0adf4dd7f83 100644 (file)
--- a/target/ppc/translate.c
+++ b/target/ppc/translate.c
@@ -75,7 +75,9 @@ static TCGv cpu_xer, cpu_so, cpu_ov, cpu_ca, cpu_ov32, cpu_ca32;
 static TCGv cpu_reserve;
 static TCGv cpu_reserve_length;
 static TCGv cpu_reserve_val;
+#if defined(TARGET_PPC64)
 static TCGv cpu_reserve_val2;
+#endif
 static TCGv cpu_fpscr;
 static TCGv_i32 cpu_access_type;
 
@@ -149,9 +151,11 @@ void ppc_translate_init(void)
     cpu_reserve_val = tcg_global_mem_new(cpu_env,
                                          offsetof(CPUPPCState, reserve_val),
                                          "reserve_val");
+#if defined(TARGET_PPC64)
     cpu_reserve_val2 = tcg_global_mem_new(cpu_env,
                                           offsetof(CPUPPCState, reserve_val2),
                                           "reserve_val2");
+#endif
 
     cpu_fpscr = tcg_global_mem_new(cpu_env,
                                    offsetof(CPUPPCState, fpscr), "fpscr");