From 1f6493be088da969efeeee0100ea4330fb804cdf Mon Sep 17 00:00:00 2001 From: David Hildenbrand Date: Tue, 1 Oct 2019 20:03:54 +0200 Subject: [PATCH] s390x/tcg: MVCL: Exit to main loop if requested MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit MVCL is interruptible and we should check for interrupts and process them after writing back the variables to the registers. Let's check for any exit requests and exit to the main loop. Introduce a new helper function for that: cpu_loop_exit_requested(). When booting Fedora 30, I can see a handful of these exits and it seems to work reliable. Also, Richard explained why this works correctly even when MVCL is called via EXECUTE: (1) TB with EXECUTE runs, at address Ae - env->psw_addr stored with Ae. - helper_ex() runs, memory address Am computed from D2a(X2a,B2a) or from psw.addr+RI2. - env->ex_value stored with memory value modified by R1a (2) TB of executee runs, - env->ex_value stored with 0. - helper_mvcl() runs, using and updating R1b, R1b+1, R2b, R2b+1. (3a) helper_mvcl() completes, - TB of executee continues, psw.addr += ilen. - Next instruction is the one following EXECUTE. (3b) helper_mvcl() exits to main loop, - cpu_loop_exit_restore() unwinds psw.addr = Ae. - Next instruction is the EXECUTE itself... - goto 1. As the PoP mentiones that an interruptible instruction called via EXECUTE should avoid modifying storage/registers that are used by EXECUTE itself, it is fine to retrigger EXECUTE. Cc: Alex Bennée Cc: Peter Maydell Cc: Paolo Bonzini Suggested-by: Richard Henderson Reviewed-by: Richard Henderson Reviewed-by: Alex Bennée Signed-off-by: David Hildenbrand --- include/exec/exec-all.h | 17 +++++++++++++++++ target/s390x/mem_helper.c | 11 ++++++++++- 2 files changed, 27 insertions(+), 1 deletion(-) diff --git a/include/exec/exec-all.h b/include/exec/exec-all.h index 49db07ba0b..04795c49bf 100644 --- a/include/exec/exec-all.h +++ b/include/exec/exec-all.h @@ -72,6 +72,23 @@ void QEMU_NORETURN cpu_loop_exit(CPUState *cpu); void QEMU_NORETURN cpu_loop_exit_restore(CPUState *cpu, uintptr_t pc); void QEMU_NORETURN cpu_loop_exit_atomic(CPUState *cpu, uintptr_t pc); +/** + * cpu_loop_exit_requested: + * @cpu: The CPU state to be tested + * + * Indicate if somebody asked for a return of the CPU to the main loop + * (e.g., via cpu_exit() or cpu_interrupt()). + * + * This is helpful for architectures that support interruptible + * instructions. After writing back all state to registers/memory, this + * call can be used to check if it makes sense to return to the main loop + * or to continue executing the interruptible instruction. + */ +static inline bool cpu_loop_exit_requested(CPUState *cpu) +{ + return (int32_t)atomic_read(&cpu_neg(cpu)->icount_decr.u32) < 0; +} + #if !defined(CONFIG_USER_ONLY) void cpu_reloading_memory_map(void); /** diff --git a/target/s390x/mem_helper.c b/target/s390x/mem_helper.c index 4254548935..2325767f17 100644 --- a/target/s390x/mem_helper.c +++ b/target/s390x/mem_helper.c @@ -1015,6 +1015,7 @@ uint32_t HELPER(mvcl)(CPUS390XState *env, uint32_t r1, uint32_t r2) uint64_t srclen = env->regs[r2 + 1] & 0xffffff; uint64_t src = get_address(env, r2); uint8_t pad = env->regs[r2 + 1] >> 24; + CPUState *cs = env_cpu(env); S390Access srca, desta; uint32_t cc, cur_len; @@ -1065,7 +1066,15 @@ uint32_t HELPER(mvcl)(CPUS390XState *env, uint32_t r1, uint32_t r2) env->regs[r1 + 1] = deposit64(env->regs[r1 + 1], 0, 24, destlen); set_address_zero(env, r1, dest); - /* TODO: Deliver interrupts. */ + /* + * MVCL is interruptible. Return to the main loop if requested after + * writing back all state to registers. If no interrupt will get + * injected, we'll end up back in this handler and continue processing + * the remaining parts. + */ + if (destlen && unlikely(cpu_loop_exit_requested(cs))) { + cpu_loop_exit_restore(cs, ra); + } } return cc; } -- 2.11.0