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

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ppc only migrates reserve_addr, so the destination machine can get a
valid reservation with an incorrect reservation value of 0. Prior to
commit 392d328abe ("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>
This commit is contained in:
Nicholas Piggin 2023-08-08 14:19:55 +10:00 • committed by Cédric Le Goater
parent ea62f8a517
commit cdab53dd22
3 changed files with 30 additions and 2 deletions
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4
target/ppc/translate.c
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@ -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");