Re: [PATCH v8 08/25] tcg: drop global lock during TCG code execution

["Alex Bennée" <alex.bennee@linaro.org>]

Pranith Kumar <bobby.prani@gmail.com> writes:

> Alex Bennée writes:
>
>> From: Jan Kiszka <jan.kiszka@siemens.com>
>>
>> This finally allows TCG to benefit from the iothread introduction: Drop
>> the global mutex while running pure TCG CPU code. Reacquire the lock
>> when entering MMIO or PIO emulation, or when leaving the TCG loop.
>>
>> We have to revert a few optimization for the current TCG threading
>> model, namely kicking the TCG thread in qemu_mutex_lock_iothread and not
>> kicking it in qemu_cpu_kick. We also need to disable RAM block
>> reordering until we have a more efficient locking mechanism at hand.
>>
>> Still, a Linux x86 UP guest and my Musicpal ARM model boot fine here.
>> These numbers demonstrate where we gain something:
>>
>> 20338 jan       20   0  331m  75m 6904 R   99  0.9   0:50.95 qemu-system-arm
>> 20337 jan       20   0  331m  75m 6904 S   20  0.9   0:26.50 qemu-system-arm
>>
>> The guest CPU was fully loaded, but the iothread could still run mostly
>> independent on a second core. Without the patch we don't get beyond
>>
>> 32206 jan       20   0  330m  73m 7036 R   82  0.9   1:06.00 qemu-system-arm
>> 32204 jan       20   0  330m  73m 7036 S   21  0.9   0:17.03 qemu-system-arm
>>
>> We don't benefit significantly, though, when the guest is not fully
>> loading a host CPU.
>>
>> Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
>> Message-Id: <1439220437-23957-10-git-send-email-fred.konrad@greensocs.com>
>> [FK: Rebase, fix qemu_devices_reset deadlock, rm address_space_* mutex]
>> Signed-off-by: KONRAD Frederic <fred.konrad@greensocs.com>
>> [EGC: fixed iothread lock for cpu-exec IRQ handling]
>> Signed-off-by: Emilio G. Cota <cota@braap.org>
>> [AJB: -smp single-threaded fix, clean commit msg, BQL fixes]
>> Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
>> Reviewed-by: Richard Henderson <rth@twiddle.net>
>>
>> ---
>> v8:
>>  - merged in BQL fixes for PPC target: ppc_set_irq
>>  - merged in BQL fixes for ARM target: ARM_CP_IO helpers
>>  - merged in BQL fixes for ARM target: arm_call_el_change_hook
>>
>> v5 (ajb, base patches):
>>  - added an assert to BQL unlock/lock functions instead of hanging
>>  - ensure all cpu->interrupt_requests *modifications* protected by BQL
>>  - add a re-read on cpu->interrupt_request for correctness
>>  - BQL fixes for:
>>    - assert BQL held for PPC hypercalls (emulate_spar_hypercall)
>>    - SCLP service calls on s390x
>>  - merge conflict with kick timer patch
>> v4 (ajb, base patches):
>>  - protect cpu->interrupt updates with BQL
>>  - fix wording io_mem_notdirty calls
>>  - s/we/with/
>> v3 (ajb, base-patches):
>>   - stale iothread_unlocks removed (cpu_exit/resume_from_signal deals
>>   with it in the longjmp).
>>   - fix re-base conflicts
>> v2 (ajb):
>>   - merge with tcg: grab iothread lock in cpu-exec interrupt handling
>>   - use existing fns for tracking lock state
>>   - lock iothread for mem_region
>>     - add assert on mem region modification
>>     - ensure smm_helper holds iothread
>>   - Add JK s-o-b
>>   - Fix-up FK s-o-b annotation
>> v1 (ajb, base-patches):
>>   - SMP failure now fixed by previous commit
>>
>> Changes from Fred Konrad (mttcg-v7 via paolo):
>>   * Rebase on the current HEAD.
>>   * Fixes a deadlock in qemu_devices_reset().
>>   * Remove the mutex in address_space_*
>> ---
>>  cpu-exec.c                 | 20 ++++++++++++++++++--
>>  cpus.c                     | 28 +++++-----------------------
>>  cputlb.c                   | 21 ++++++++++++++++++++-
>>  exec.c                     | 12 +++++++++---
>>  hw/core/irq.c              |  1 +
>>  hw/i386/kvmvapic.c         |  4 ++--
>>  hw/intc/arm_gicv3_cpuif.c  |  3 +++
>>  hw/ppc/ppc.c               | 16 +++++++++++++++-
>>  hw/ppc/spapr.c             |  3 +++
>>  include/qom/cpu.h          |  1 +
>>  memory.c                   |  2 ++
>>  qom/cpu.c                  | 10 ++++++++++
>>  target/arm/helper.c        |  6 ++++++
>>  target/arm/op_helper.c     | 43 +++++++++++++++++++++++++++++++++++++++----
>>  target/i386/smm_helper.c   |  7 +++++++
>>  target/s390x/misc_helper.c |  5 ++++-
>>  translate-all.c            |  9 +++++++--
>>  translate-common.c         | 21 +++++++++++----------
>>  18 files changed, 163 insertions(+), 49 deletions(-)
>>
>> diff --git a/cpu-exec.c b/cpu-exec.c
>> index f9e836c8dd..f42a128bdf 100644
>> --- a/cpu-exec.c
>> +++ b/cpu-exec.c
>> @@ -29,6 +29,7 @@
>>  #include "qemu/rcu.h"
>>  #include "exec/tb-hash.h"
>>  #include "exec/log.h"
>> +#include "qemu/main-loop.h"
>>  #if defined(TARGET_I386) && !defined(CONFIG_USER_ONLY)
>>  #include "hw/i386/apic.h"
>>  #endif
>> @@ -388,8 +389,10 @@ static inline bool cpu_handle_halt(CPUState *cpu)
>>          if ((cpu->interrupt_request & CPU_INTERRUPT_POLL)
>>              && replay_interrupt()) {
>>              X86CPU *x86_cpu = X86_CPU(cpu);
>> +            qemu_mutex_lock_iothread();
>>              apic_poll_irq(x86_cpu->apic_state);
>>              cpu_reset_interrupt(cpu, CPU_INTERRUPT_POLL);
>> +            qemu_mutex_unlock_iothread();
>>          }
>>  #endif
>>          if (!cpu_has_work(cpu)) {
>> @@ -443,7 +446,9 @@ static inline bool cpu_handle_exception(CPUState *cpu, int *ret)
>>  #else
>>              if (replay_exception()) {
>>                  CPUClass *cc = CPU_GET_CLASS(cpu);
>> +                qemu_mutex_lock_iothread();
>>                  cc->do_interrupt(cpu);
>> +                qemu_mutex_unlock_iothread();
>>                  cpu->exception_index = -1;
>>              } else if (!replay_has_interrupt()) {
>>                  /* give a chance to iothread in replay mode */
>> @@ -469,9 +474,11 @@ static inline void cpu_handle_interrupt(CPUState *cpu,
>>                                          TranslationBlock **last_tb)
>>  {
>>      CPUClass *cc = CPU_GET_CLASS(cpu);
>> -    int interrupt_request = cpu->interrupt_request;
>>
>> -    if (unlikely(interrupt_request)) {
>> +    if (unlikely(atomic_read(&cpu->interrupt_request))) {
>> +        int interrupt_request;
>> +        qemu_mutex_lock_iothread();
>> +        interrupt_request = cpu->interrupt_request;
>>          if (unlikely(cpu->singlestep_enabled & SSTEP_NOIRQ)) {
>>              /* Mask out external interrupts for this step. */
>>              interrupt_request &= ~CPU_INTERRUPT_SSTEP_MASK;
>> @@ -526,7 +533,12 @@ static inline void cpu_handle_interrupt(CPUState *cpu,
>>                 the program flow was changed */
>>              *last_tb = NULL;
>>          }
>> +
>> +        /* If we exit via cpu_loop_exit/longjmp it is reset in cpu_exec */
>> +        qemu_mutex_unlock_iothread();
>>      }
>> +
>> +
>>      if (unlikely(atomic_read(&cpu->exit_request) || replay_has_interrupt())) {
>>          atomic_set(&cpu->exit_request, 0);
>>          cpu->exception_index = EXCP_INTERRUPT;
>> @@ -656,8 +668,12 @@ int cpu_exec(CPUState *cpu)
>>              g_assert(cpu == current_cpu);
>>              g_assert(cc == CPU_GET_CLASS(cpu));
>>  #endif /* buggy compiler */
>> +
>>              cpu->can_do_io = 1;
>>              tb_lock_reset();
>> +            if (qemu_mutex_iothread_locked()) {
>> +                qemu_mutex_unlock_iothread();
>> +            }
>>          }
>>      } /* for(;;) */
>>
>> diff --git a/cpus.c b/cpus.c
>> index 6d64199831..c48bc8d5b3 100644
>> --- a/cpus.c
>> +++ b/cpus.c
>> @@ -1026,8 +1026,6 @@ static void qemu_kvm_init_cpu_signals(CPUState *cpu)
>>  #endif /* _WIN32 */
>>
>>  static QemuMutex qemu_global_mutex;
>> -static QemuCond qemu_io_proceeded_cond;
>> -static unsigned iothread_requesting_mutex;
>>
>>  static QemuThread io_thread;
>>
>> @@ -1041,7 +1039,6 @@ void qemu_init_cpu_loop(void)
>>      qemu_init_sigbus();
>>      qemu_cond_init(&qemu_cpu_cond);
>>      qemu_cond_init(&qemu_pause_cond);
>> -    qemu_cond_init(&qemu_io_proceeded_cond);
>>      qemu_mutex_init(&qemu_global_mutex);
>>
>>      qemu_thread_get_self(&io_thread);
>> @@ -1084,10 +1081,6 @@ static void qemu_tcg_wait_io_event(CPUState *cpu)
>>
>>      start_tcg_kick_timer();
>>
>> -    while (iothread_requesting_mutex) {
>> -        qemu_cond_wait(&qemu_io_proceeded_cond, &qemu_global_mutex);
>> -    }
>> -
>>      CPU_FOREACH(cpu) {
>>          qemu_wait_io_event_common(cpu);
>>      }
>> @@ -1248,9 +1241,11 @@ static int tcg_cpu_exec(CPUState *cpu)
>>          cpu->icount_decr.u16.low = decr;
>>          cpu->icount_extra = count;
>>      }
>> +    qemu_mutex_unlock_iothread();
>>      cpu_exec_start(cpu);
>>      ret = cpu_exec(cpu);
>>      cpu_exec_end(cpu);
>> +    qemu_mutex_lock_iothread();
>>  #ifdef CONFIG_PROFILER
>>      tcg_time += profile_getclock() - ti;
>>  #endif
>> @@ -1478,27 +1473,14 @@ bool qemu_mutex_iothread_locked(void)
>>
>>  void qemu_mutex_lock_iothread(void)
>>  {
>> -    atomic_inc(&iothread_requesting_mutex);
>> -    /* In the simple case there is no need to bump the VCPU thread out of
>> -     * TCG code execution.
>> -     */
>> -    if (!tcg_enabled() || qemu_in_vcpu_thread() ||
>> -        !first_cpu || !first_cpu->created) {
>> -        qemu_mutex_lock(&qemu_global_mutex);
>> -        atomic_dec(&iothread_requesting_mutex);
>> -    } else {
>> -        if (qemu_mutex_trylock(&qemu_global_mutex)) {
>> -            qemu_cpu_kick_rr_cpu();
>> -            qemu_mutex_lock(&qemu_global_mutex);
>> -        }
>> -        atomic_dec(&iothread_requesting_mutex);
>> -        qemu_cond_broadcast(&qemu_io_proceeded_cond);
>> -    }
>> +    g_assert(!qemu_mutex_iothread_locked());
>
> How about using tcg_debug_assert here...
>
>> +    qemu_mutex_lock(&qemu_global_mutex);
>>      iothread_locked = true;
>>  }
>>
>>  void qemu_mutex_unlock_iothread(void)
>>  {
>> +    g_assert(qemu_mutex_iothread_locked());
>
> ... and here?

The iothread mutex is widely used in QEMU for bits other than TCG. In
fact I think it was introduced when KVM support was merged. As such I
don't want to remove these asserts from KVM mode.

It does mean this patch is slowly accreteing fixes for the BQL being
taken up by system emulation code though.

>
>>      iothread_locked = false;
>>      qemu_mutex_unlock(&qemu_global_mutex);
>>  }
>> diff --git a/cputlb.c b/cputlb.c
>> index 6c39927455..1cc9d9da51 100644
>> --- a/cputlb.c
>> +++ b/cputlb.c
>> @@ -18,6 +18,7 @@
>>   */
>>
>>  #include "qemu/osdep.h"
>> +#include "qemu/main-loop.h"
>>  #include "cpu.h"
>>  #include "exec/exec-all.h"
>>  #include "exec/memory.h"
>> @@ -495,6 +496,7 @@ static uint64_t io_readx(CPUArchState *env, CPUIOTLBEntry *iotlbentry,
>>      hwaddr physaddr = iotlbentry->addr;
>>      MemoryRegion *mr = iotlb_to_region(cpu, physaddr, iotlbentry->attrs);
>>      uint64_t val;
>> +    bool locked = false;
>>
>>      physaddr = (physaddr & TARGET_PAGE_MASK) + addr;
>>      cpu->mem_io_pc = retaddr;
>> @@ -503,7 +505,16 @@ static uint64_t io_readx(CPUArchState *env, CPUIOTLBEntry *iotlbentry,
>>      }
>>
>>      cpu->mem_io_vaddr = addr;
>> +
>> +    if (mr->global_locking) {
>> +        qemu_mutex_lock_iothread();
>> +        locked = true;
>> +    }
>>      memory_region_dispatch_read(mr, physaddr, &val, size, iotlbentry->attrs);
>> +    if (locked) {
>> +        qemu_mutex_unlock_iothread();
>> +    }
>> +
>>      return val;
>>  }
>>
>> @@ -514,15 +525,23 @@ static void io_writex(CPUArchState *env, CPUIOTLBEntry *iotlbentry,
>>      CPUState *cpu = ENV_GET_CPU(env);
>>      hwaddr physaddr = iotlbentry->addr;
>>      MemoryRegion *mr = iotlb_to_region(cpu, physaddr, iotlbentry->attrs);
>> +    bool locked = false;
>>
>>      physaddr = (physaddr & TARGET_PAGE_MASK) + addr;
>>      if (mr != &io_mem_rom && mr != &io_mem_notdirty && !cpu->can_do_io) {
>>          cpu_io_recompile(cpu, retaddr);
>>      }
>> -
>
> I am not really opposed but, I like having this line.. not sure why
> you are removing it? :)

Over zealous whitespace trimming, I can put it back ;-)

>
>>      cpu->mem_io_vaddr = addr;
>>      cpu->mem_io_pc = retaddr;
>> +
>> +    if (mr->global_locking) {
>> +        qemu_mutex_lock_iothread();
>> +        locked = true;
>> +    }
>>      memory_region_dispatch_write(mr, physaddr, val, size, iotlbentry->attrs);
>> +    if (locked) {
>> +        qemu_mutex_unlock_iothread();
>> +    }
>>  }
>>
>>  /* Return true if ADDR is present in the victim tlb, and has been copied
>> diff --git a/exec.c b/exec.c
>> index f2bed92b64..87cf0db91e 100644
>> --- a/exec.c
>> +++ b/exec.c
>> @@ -2133,9 +2133,9 @@ static void check_watchpoint(int offset, int len, MemTxAttrs attrs, int flags)
>>                  }
>>                  cpu->watchpoint_hit = wp;
>>
>> -                /* The tb_lock will be reset when cpu_loop_exit or
>> -                 * cpu_loop_exit_noexc longjmp back into the cpu_exec
>> -                 * main loop.
>> +                /* Both tb_lock and iothread_mutex will be reset when
>> +                 * cpu_loop_exit or cpu_loop_exit_noexc longjmp
>> +                 * back into the cpu_exec main loop.
>>                   */
>>                  tb_lock();
>>                  tb_check_watchpoint(cpu);
>> @@ -2370,8 +2370,14 @@ static void io_mem_init(void)
>>      memory_region_init_io(&io_mem_rom, NULL, &unassigned_mem_ops, NULL, NULL, UINT64_MAX);
>>      memory_region_init_io(&io_mem_unassigned, NULL, &unassigned_mem_ops, NULL,
>>                            NULL, UINT64_MAX);
>> +
>> +    /* io_mem_notdirty calls tb_invalidate_phys_page_fast,
>> +     * which can be called without the iothread mutex.
>> +     */
>>      memory_region_init_io(&io_mem_notdirty, NULL, &notdirty_mem_ops, NULL,
>>                            NULL, UINT64_MAX);
>> +    memory_region_clear_global_locking(&io_mem_notdirty);
>> +
>>      memory_region_init_io(&io_mem_watch, NULL, &watch_mem_ops, NULL,
>>                            NULL, UINT64_MAX);
>>  }
>> diff --git a/hw/core/irq.c b/hw/core/irq.c
>> index 49ff2e64fe..b98d1d69f5 100644
>> --- a/hw/core/irq.c
>> +++ b/hw/core/irq.c
>> @@ -22,6 +22,7 @@
>>   * THE SOFTWARE.
>>   */
>>  #include "qemu/osdep.h"
>> +#include "qemu/main-loop.h"
>>  #include "qemu-common.h"
>>  #include "hw/irq.h"
>>  #include "qom/object.h"
>> diff --git a/hw/i386/kvmvapic.c b/hw/i386/kvmvapic.c
>> index 702e281dc8..b3c49b2c61 100644
>> --- a/hw/i386/kvmvapic.c
>> +++ b/hw/i386/kvmvapic.c
>> @@ -451,8 +451,8 @@ static void patch_instruction(VAPICROMState *s, X86CPU *cpu, target_ulong ip)
>>      resume_all_vcpus();
>>
>>      if (!kvm_enabled()) {
>> -        /* tb_lock will be reset when cpu_loop_exit_noexc longjmps
>> -         * back into the cpu_exec loop. */
>> +        /* Both tb_lock and iothread_mutex will be reset when
>> +         *  longjmps back into the cpu_exec loop. */
>
> missing cpu_loop_exit_noexc?

Well cpu_exec is the main loop, even if cpu_loop_exit_noexc is what
takes you there. I'll see if I can make it clearer:

      /* Both tb_lock and iothread_mutex will be reset when
         cpu_loop_exit_noexc longjmps back into the cpu_exec loop */

>
>>          tb_lock();
>>          tb_gen_code(cs, current_pc, current_cs_base, current_flags, 1);
>>          cpu_loop_exit_noexc(cs);
>> diff --git a/hw/intc/arm_gicv3_cpuif.c b/hw/intc/arm_gicv3_cpuif.c
>> index a9ee7fddf9..2624d8d909 100644
>> --- a/hw/intc/arm_gicv3_cpuif.c
>> +++ b/hw/intc/arm_gicv3_cpuif.c
>> @@ -14,6 +14,7 @@
>>
>>  #include "qemu/osdep.h"
>>  #include "qemu/bitops.h"
>> +#include "qemu/main-loop.h"
>>  #include "trace.h"
>>  #include "gicv3_internal.h"
>>  #include "cpu.h"
>> @@ -733,6 +734,8 @@ void gicv3_cpuif_update(GICv3CPUState *cs)
>>      ARMCPU *cpu = ARM_CPU(cs->cpu);
>>      CPUARMState *env = &cpu->env;
>>
>> +    g_assert(qemu_mutex_iothread_locked());
>> +
>
> tcg_debug_assert()?

Depends if KVM can use this for emulation as well (which I think it can).

>
>>      trace_gicv3_cpuif_update(gicv3_redist_affid(cs), cs->hppi.irq,
>>                               cs->hppi.grp, cs->hppi.prio);
>>
>> diff --git a/hw/ppc/ppc.c b/hw/ppc/ppc.c
>> index 8945869009..59c3faa6c8 100644
>> --- a/hw/ppc/ppc.c
>> +++ b/hw/ppc/ppc.c
>> @@ -62,7 +62,16 @@ void ppc_set_irq(PowerPCCPU *cpu, int n_IRQ, int level)
>>  {
>>      CPUState *cs = CPU(cpu);
>>      CPUPPCState *env = &cpu->env;
>> -    unsigned int old_pending = env->pending_interrupts;
>> +    unsigned int old_pending;
>> +    bool locked = false;
>> +
>> +    /* We may already have the BQL if coming from the reset path */
>> +    if (!qemu_mutex_iothread_locked()) {
>> +        locked = true;
>> +        qemu_mutex_lock_iothread();
>> +    }
>> +
>> +    old_pending = env->pending_interrupts;
>>
>>      if (level) {
>>          env->pending_interrupts |= 1 << n_IRQ;
>> @@ -80,9 +89,14 @@ void ppc_set_irq(PowerPCCPU *cpu, int n_IRQ, int level)
>>  #endif
>>      }
>>
>> +
>>      LOG_IRQ("%s: %p n_IRQ %d level %d => pending %08" PRIx32
>>                  "req %08x\n", __func__, env, n_IRQ, level,
>>                  env->pending_interrupts, CPU(cpu)->interrupt_request);
>> +
>> +    if (locked) {
>> +        qemu_mutex_unlock_iothread();
>> +    }
>>  }
>>
>>  /* PowerPC 6xx / 7xx internal IRQ controller */
>> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
>> index a642e663d4..745743d64b 100644
>> --- a/hw/ppc/spapr.c
>> +++ b/hw/ppc/spapr.c
>> @@ -1012,6 +1012,9 @@ static void emulate_spapr_hypercall(PowerPCCPU *cpu)
>>  {
>>      CPUPPCState *env = &cpu->env;
>>
>> +    /* The TCG path should also be holding the BQL at this point */
>> +    g_assert(qemu_mutex_iothread_locked());
>> +
>
> tcg_debug_assert()?
>
>>      if (msr_pr) {
>>          hcall_dprintf("Hypercall made with MSR[PR]=1\n");
>>          env->gpr[3] = H_PRIVILEGE;
>> diff --git a/include/qom/cpu.h b/include/qom/cpu.h
>> index 11db2015a4..1a06ae5938 100644
>> --- a/include/qom/cpu.h
>> +++ b/include/qom/cpu.h
>> @@ -325,6 +325,7 @@ struct CPUState {
>>      bool unplug;
>>      bool crash_occurred;
>>      bool exit_request;
>> +    /* updates protected by BQL */
>>      uint32_t interrupt_request;
>>      int singlestep_enabled;
>>      int64_t icount_extra;
>> diff --git a/memory.c b/memory.c
>> index 2bfc37f65c..7d7b285e41 100644
>> --- a/memory.c
>> +++ b/memory.c
>> @@ -917,6 +917,8 @@ void memory_region_transaction_commit(void)
>>      AddressSpace *as;
>>
>>      assert(memory_region_transaction_depth);
>> +    assert(qemu_mutex_iothread_locked());
>> +
>>      --memory_region_transaction_depth;
>>      if (!memory_region_transaction_depth) {
>>          if (memory_region_update_pending) {
>> diff --git a/qom/cpu.c b/qom/cpu.c
>> index 7f575879f6..bd77c05cd0 100644
>> --- a/qom/cpu.c
>> +++ b/qom/cpu.c
>> @@ -113,9 +113,19 @@ static void cpu_common_get_memory_mapping(CPUState *cpu,
>>      error_setg(errp, "Obtaining memory mappings is unsupported on this CPU.");
>>  }
>>
>> +/* Resetting the IRQ comes from across the code base so we take the
>> + * BQL here if we need to.  cpu_interrupt assumes it is held.*/
>>  void cpu_reset_interrupt(CPUState *cpu, int mask)
>>  {
>> +    bool need_lock = !qemu_mutex_iothread_locked();
>> +
>> +    if (need_lock) {
>> +        qemu_mutex_lock_iothread();
>> +    }
>>      cpu->interrupt_request &= ~mask;
>> +    if (need_lock) {
>> +        qemu_mutex_unlock_iothread();
>> +    }
>>  }
>>
>>  void cpu_exit(CPUState *cpu)
>> diff --git a/target/arm/helper.c b/target/arm/helper.c
>> index 7111c8cf18..84d789be93 100644
>> --- a/target/arm/helper.c
>> +++ b/target/arm/helper.c
>> @@ -6693,6 +6693,12 @@ void arm_cpu_do_interrupt(CPUState *cs)
>>          arm_cpu_do_interrupt_aarch32(cs);
>>      }
>>
>> +    /* Hooks may change global state so BQL should be held, also the
>> +     * BQL needs to be held for any modification of
>> +     * cs->interrupt_request.
>> +     */
>> +    g_assert(qemu_mutex_iothread_locked());
>> +
>>      arm_call_el_change_hook(cpu);
>>
>>      if (!kvm_enabled()) {
>> diff --git a/target/arm/op_helper.c b/target/arm/op_helper.c
>> index ba796d898e..e1a883c595 100644
>> --- a/target/arm/op_helper.c
>> +++ b/target/arm/op_helper.c
>> @@ -18,6 +18,7 @@
>>   */
>>  #include "qemu/osdep.h"
>>  #include "qemu/log.h"
>> +#include "qemu/main-loop.h"
>>  #include "cpu.h"
>>  #include "exec/helper-proto.h"
>>  #include "internals.h"
>> @@ -487,7 +488,9 @@ void HELPER(cpsr_write_eret)(CPUARMState *env, uint32_t val)
>>       */
>>      env->regs[15] &= (env->thumb ? ~1 : ~3);
>>
>> +    qemu_mutex_lock_iothread();
>>      arm_call_el_change_hook(arm_env_get_cpu(env));
>> +    qemu_mutex_unlock_iothread();
>>  }
>>
>>  /* Access to user mode registers from privileged modes.  */
>> @@ -735,28 +738,58 @@ void HELPER(set_cp_reg)(CPUARMState *env, void *rip, uint32_t value)
>>  {
>>      const ARMCPRegInfo *ri = rip;
>>
>> -    ri->writefn(env, ri, value);
>> +    if (ri->type & ARM_CP_IO) {
>> +        qemu_mutex_lock_iothread();
>> +        ri->writefn(env, ri, value);
>> +        qemu_mutex_unlock_iothread();
>> +    } else {
>> +        ri->writefn(env, ri, value);
>> +    }
>>  }
>>
>>  uint32_t HELPER(get_cp_reg)(CPUARMState *env, void *rip)
>>  {
>>      const ARMCPRegInfo *ri = rip;
>> +    uint32_t res;
>>
>> -    return ri->readfn(env, ri);
>> +    if (ri->type & ARM_CP_IO) {
>> +        qemu_mutex_lock_iothread();
>> +        res = ri->readfn(env, ri);
>> +        qemu_mutex_unlock_iothread();
>> +    } else {
>> +        res = ri->readfn(env, ri);
>> +    }
>> +
>> +    return res;
>>  }
>>
>>  void HELPER(set_cp_reg64)(CPUARMState *env, void *rip, uint64_t value)
>>  {
>>      const ARMCPRegInfo *ri = rip;
>>
>> -    ri->writefn(env, ri, value);
>> +    if (ri->type & ARM_CP_IO) {
>> +        qemu_mutex_lock_iothread();
>> +        ri->writefn(env, ri, value);
>> +        qemu_mutex_unlock_iothread();
>> +    } else {
>> +        ri->writefn(env, ri, value);
>> +    }
>>  }
>>
>>  uint64_t HELPER(get_cp_reg64)(CPUARMState *env, void *rip)
>>  {
>>      const ARMCPRegInfo *ri = rip;
>> +    uint64_t res;
>> +
>> +    if (ri->type & ARM_CP_IO) {
>> +        qemu_mutex_lock_iothread();
>> +        res = ri->readfn(env, ri);
>> +        qemu_mutex_unlock_iothread();
>> +    } else {
>> +        res = ri->readfn(env, ri);
>> +    }
>>
>> -    return ri->readfn(env, ri);
>> +    return res;
>>  }
>>
>>  void HELPER(msr_i_pstate)(CPUARMState *env, uint32_t op, uint32_t imm)
>> @@ -989,7 +1022,9 @@ void HELPER(exception_return)(CPUARMState *env)
>>                        cur_el, new_el, env->pc);
>>      }
>>
>> +    qemu_mutex_lock_iothread();
>>      arm_call_el_change_hook(arm_env_get_cpu(env));
>> +    qemu_mutex_unlock_iothread();
>>
>>      return;
>>
>> diff --git a/target/i386/smm_helper.c b/target/i386/smm_helper.c
>> index 4dd6a2c544..f051a77c4a 100644
>> --- a/target/i386/smm_helper.c
>> +++ b/target/i386/smm_helper.c
>> @@ -18,6 +18,7 @@
>>   */
>>
>>  #include "qemu/osdep.h"
>> +#include "qemu/main-loop.h"
>>  #include "cpu.h"
>>  #include "exec/helper-proto.h"
>>  #include "exec/log.h"
>> @@ -42,11 +43,14 @@ void helper_rsm(CPUX86State *env)
>>  #define SMM_REVISION_ID 0x00020000
>>  #endif
>>
>> +/* Called with iothread lock taken */
>>  void cpu_smm_update(X86CPU *cpu)
>>  {
>>      CPUX86State *env = &cpu->env;
>>      bool smm_enabled = (env->hflags & HF_SMM_MASK);
>>
>> +    g_assert(qemu_mutex_iothread_locked());
>> +
>>      if (cpu->smram) {
>>          memory_region_set_enabled(cpu->smram, smm_enabled);
>>      }
>> @@ -333,7 +337,10 @@ void helper_rsm(CPUX86State *env)
>>      }
>>      env->hflags2 &= ~HF2_SMM_INSIDE_NMI_MASK;
>>      env->hflags &= ~HF_SMM_MASK;
>> +
>> +    qemu_mutex_lock_iothread();
>>      cpu_smm_update(cpu);
>> +    qemu_mutex_unlock_iothread();
>>
>>      qemu_log_mask(CPU_LOG_INT, "SMM: after RSM\n");
>>      log_cpu_state_mask(CPU_LOG_INT, CPU(cpu), CPU_DUMP_CCOP);
>> diff --git a/target/s390x/misc_helper.c b/target/s390x/misc_helper.c
>> index c9604ea9c7..3cb942e8bb 100644
>> --- a/target/s390x/misc_helper.c
>> +++ b/target/s390x/misc_helper.c
>> @@ -25,6 +25,7 @@
>>  #include "exec/helper-proto.h"
>>  #include "sysemu/kvm.h"
>>  #include "qemu/timer.h"
>> +#include "qemu/main-loop.h"
>>  #include "exec/address-spaces.h"
>>  #ifdef CONFIG_KVM
>>  #include <linux/kvm.h>
>> @@ -109,11 +110,13 @@ void program_interrupt(CPUS390XState *env, uint32_t code, int ilen)
>>  /* SCLP service call */
>>  uint32_t HELPER(servc)(CPUS390XState *env, uint64_t r1, uint64_t r2)
>>  {
>> +    qemu_mutex_lock_iothread();
>>      int r = sclp_service_call(env, r1, r2);
>>      if (r < 0) {
>>          program_interrupt(env, -r, 4);
>> -        return 0;
>> +        r = 0;
>>      }
>> +    qemu_mutex_unlock_iothread();
>>      return r;
>>  }
>>
>> diff --git a/translate-all.c b/translate-all.c
>> index 055436a676..41b36f04c6 100644
>> --- a/translate-all.c
>> +++ b/translate-all.c
>> @@ -55,6 +55,7 @@
>>  #include "translate-all.h"
>>  #include "qemu/bitmap.h"
>>  #include "qemu/timer.h"
>> +#include "qemu/main-loop.h"
>>  #include "exec/log.h"
>>
>>  /* #define DEBUG_TB_INVALIDATE */
>> @@ -1521,7 +1522,7 @@ void tb_invalidate_phys_page_range(tb_page_addr_t start, tb_page_addr_t end,
>>  #ifdef CONFIG_SOFTMMU
>>  /* len must be <= 8 and start must be a multiple of len.
>>   * Called via softmmu_template.h when code areas are written to with
>> - * tb_lock held.
>> + * iothread mutex not held.
>>   */
>>  void tb_invalidate_phys_page_fast(tb_page_addr_t start, int len)
>>  {
>
> Shouldn't this be both tb_lock and iothread mutex?
>
>> @@ -1723,7 +1724,10 @@ void tb_check_watchpoint(CPUState *cpu)
>>
>>  #ifndef CONFIG_USER_ONLY
>>  /* in deterministic execution mode, instructions doing device I/Os
>> -   must be at the end of the TB */
>> + * must be at the end of the TB.
>> + *
>> + * Called by softmmu_template.h, with iothread mutex not held.
>> + */
>>  void cpu_io_recompile(CPUState *cpu, uintptr_t retaddr)
>>  {
>>  #if defined(TARGET_MIPS) || defined(TARGET_SH4)
>> @@ -1935,6 +1939,7 @@ void dump_opcount_info(FILE *f, fprintf_function cpu_fprintf)
>>
>>  void cpu_interrupt(CPUState *cpu, int mask)
>>  {
>> +    g_assert(qemu_mutex_iothread_locked());
>>      cpu->interrupt_request |= mask;
>>      cpu->tcg_exit_req = 1;
>>  }
>> diff --git a/translate-common.c b/translate-common.c
>> index 5e989cdf70..d504dd0d33 100644
>> --- a/translate-common.c
>> +++ b/translate-common.c
>> @@ -21,6 +21,7 @@
>>  #include "qemu-common.h"
>>  #include "qom/cpu.h"
>>  #include "sysemu/cpus.h"
>> +#include "qemu/main-loop.h"
>>
>>  uintptr_t qemu_real_host_page_size;
>>  intptr_t qemu_real_host_page_mask;
>> @@ -30,6 +31,7 @@ intptr_t qemu_real_host_page_mask;
>>  static void tcg_handle_interrupt(CPUState *cpu, int mask)
>>  {
>>      int old_mask;
>> +    g_assert(qemu_mutex_iothread_locked());
>>
>>      old_mask = cpu->interrupt_request;
>>      cpu->interrupt_request |= mask;
>> @@ -40,17 +42,16 @@ static void tcg_handle_interrupt(CPUState *cpu, int mask)
>>       */
>>      if (!qemu_cpu_is_self(cpu)) {
>>          qemu_cpu_kick(cpu);
>> -        return;
>> -    }
>> -
>> -    if (use_icount) {
>> -        cpu->icount_decr.u16.high = 0xffff;
>> -        if (!cpu->can_do_io
>> -            && (mask & ~old_mask) != 0) {
>> -            cpu_abort(cpu, "Raised interrupt while not in I/O function");
>> -        }
>>      } else {
>> -        cpu->tcg_exit_req = 1;
>> +        if (use_icount) {
>> +            cpu->icount_decr.u16.high = 0xffff;
>> +            if (!cpu->can_do_io
>> +                && (mask & ~old_mask) != 0) {
>> +                cpu_abort(cpu, "Raised interrupt while not in I/O function");
>> +            }
>> +        } else {
>> +            cpu->tcg_exit_req = 1;
>> +        }
>>      }
>>  }
>
> Reviewed-by: Pranith Kumar <bobby.prani@gmail.com>

Thanks.

--
Alex Bennée