Re: [Qemu-devel] [PULL 08/24] tcg: drop global lock during TCG code execution

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

Aaron Lindsay <alindsay@codeaurora.org> writes:

> On Feb 27 14:39, Alex Bennée wrote:
>>
>> Laurent Desnogues <laurent.desnogues@gmail.com> writes:
>>
>> > Hello,
>> >
>> > On Fri, Feb 24, 2017 at 12:20 PM, Alex Bennée <alex.bennee@linaro.org> wrote:
>> >> 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.
>> >
>> > I tried this patch (8d04fb55 in the repository) with the following image:
>> >
>> >    http://wiki.qemu.org/download/arm-test-0.2.tar.gz
>> >
>> > Running the image with no option works fine.  But specifying '-icount
>> > 1' results in a (guest) deadlock. Enabling some heavy logging (-d
>> > in_asm,exec) sometimes results in a 'Bad ram offset'.
>> >
>> > Is it expected that this patch breaks -icount?
>>
>> Not really. Using icount will disable MTTCG and run single threaded as
>> before. Paolo reported another icount failure so they may be related. I
>> shall have a look at it.
>>
>> Thanks for the report.
>
> I have not experienced a guest deadlock, but for me this patch makes
> booting a simple Linux distribution take about an order of magnitude
> longer when using '-icount 0' (from about 1.6 seconds to 17.9). It was
> slow enough to get to the printk the first time after recompiling that I
> killed it thinking it *had* deadlocked.
>
> `perf report` from before this patch (snipped to >1%):
>  23.81%  qemu-system-aar  perf-9267.map        [.] 0x0000000041a5cc9e
>   7.15%  qemu-system-aar  [kernel.kallsyms]    [k] 0xffffffff8172bc82
>   6.29%  qemu-system-aar  qemu-system-aarch64  [.] cpu_exec
>   4.99%  qemu-system-aar  qemu-system-aarch64  [.] tcg_gen_code
>   4.71%  qemu-system-aar  qemu-system-aarch64  [.] cpu_get_tb_cpu_state
>   4.39%  qemu-system-aar  qemu-system-aarch64  [.] tcg_optimize
>   3.28%  qemu-system-aar  qemu-system-aarch64  [.] helper_dc_zva
>   2.66%  qemu-system-aar  qemu-system-aarch64  [.] liveness_pass_1
>   1.98%  qemu-system-aar  qemu-system-aarch64  [.] qht_lookup
>   1.93%  qemu-system-aar  qemu-system-aarch64  [.] tcg_out_opc
>   1.81%  qemu-system-aar  qemu-system-aarch64  [.] get_phys_addr_lpae
>   1.71%  qemu-system-aar  qemu-system-aarch64  [.] object_class_dynamic_cast_assert
>   1.38%  qemu-system-aar  qemu-system-aarch64  [.] arm_regime_tbi1
>   1.10%  qemu-system-aar  qemu-system-aarch64  [.] arm_regime_tbi0
>
> and after this patch:
>  20.10%  qemu-system-aar  perf-3285.map        [.] 0x0000000040a3b690
> *18.08%  qemu-system-aar  [kernel.kallsyms]    [k] 0xffffffff81371865
>   7.87%  qemu-system-aar  qemu-system-aarch64  [.] cpu_exec
>   4.70%  qemu-system-aar  qemu-system-aarch64  [.] cpu_get_tb_cpu_state
> * 2.64%  qemu-system-aar  qemu-system-aarch64  [.] g_mutex_get_impl
>   2.39%  qemu-system-aar  qemu-system-aarch64  [.] gic_update
> * 1.89%  qemu-system-aar  qemu-system-aarch64  [.] pthread_mutex_unlock
>   1.61%  qemu-system-aar  qemu-system-aarch64  [.] object_class_dynamic_cast_assert
> * 1.55%  qemu-system-aar  qemu-system-aarch64  [.] pthread_mutex_lock
>   1.31%  qemu-system-aar  qemu-system-aarch64  [.] get_phys_addr_lpae
>   1.21%  qemu-system-aar  qemu-system-aarch64  [.] arm_regime_tbi0
>   1.13%  qemu-system-aar  qemu-system-aarch64  [.] arm_regime_tbi1
>
> I've put asterisks by a few suspicious mutex-related functions, though I wonder
> if the slowdowns are also partially inlined into some of the other functions.
> The kernel also jumps up, presumably from handling more mutexes?
>
> I confess I'm not familiar enough with this code to suggest optimizations, but
> I'll be glad to test any.

Please see the series Paolo posted:

  Subject: [PATCH 0/6] tcg: fix icount super slowdown
  Date: Fri,  3 Mar 2017 14:11:08 +0100
  Message-Id: <20170303131113.25898-1-pbonzini@redhat.com>

>
> -Aaron
>
>>
>> >
>> > Thanks,
>> >
>> > Laurent
>> >
>> > PS - To clarify 791158d9 works.
>> >
>> >> 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>
>> >> Reviewed-by: Pranith Kumar <bobby.prani@gmail.com>
>> >> [PM: target-arm changes]
>> >> Acked-by: Peter Maydell <peter.maydell@linaro.org>
>> >> ---
>> >>  cpu-exec.c                 | 23 +++++++++++++++++++++--
>> >>  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, 166 insertions(+), 49 deletions(-)
>> >>
>> >> diff --git a/cpu-exec.c b/cpu-exec.c
>> >> index 06a6b25564..1bd3d72002 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 bool 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;
>> >> @@ -479,6 +486,7 @@ static inline bool cpu_handle_interrupt(CPUState *cpu,
>> >>          if (interrupt_request & CPU_INTERRUPT_DEBUG) {
>> >>              cpu->interrupt_request &= ~CPU_INTERRUPT_DEBUG;
>> >>              cpu->exception_index = EXCP_DEBUG;
>> >> +            qemu_mutex_unlock_iothread();
>> >>              return true;
>> >>          }
>> >>          if (replay_mode == REPLAY_MODE_PLAY && !replay_has_interrupt()) {
>> >> @@ -488,6 +496,7 @@ static inline bool cpu_handle_interrupt(CPUState *cpu,
>> >>              cpu->interrupt_request &= ~CPU_INTERRUPT_HALT;
>> >>              cpu->halted = 1;
>> >>              cpu->exception_index = EXCP_HLT;
>> >> +            qemu_mutex_unlock_iothread();
>> >>              return true;
>> >>          }
>> >>  #if defined(TARGET_I386)
>> >> @@ -498,12 +507,14 @@ static inline bool cpu_handle_interrupt(CPUState *cpu,
>> >>              cpu_svm_check_intercept_param(env, SVM_EXIT_INIT, 0, 0);
>> >>              do_cpu_init(x86_cpu);
>> >>              cpu->exception_index = EXCP_HALTED;
>> >> +            qemu_mutex_unlock_iothread();
>> >>              return true;
>> >>          }
>> >>  #else
>> >>          else if (interrupt_request & CPU_INTERRUPT_RESET) {
>> >>              replay_interrupt();
>> >>              cpu_reset(cpu);
>> >> +            qemu_mutex_unlock_iothread();
>> >>              return true;
>> >>          }
>> >>  #endif
>> >> @@ -526,7 +537,12 @@ static inline bool 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;
>> >> @@ -643,6 +659,9 @@ int cpu_exec(CPUState *cpu)
>> >>  #endif /* buggy compiler */
>> >>          cpu->can_do_io = 1;
>> >>          tb_lock_reset();
>> >> +        if (qemu_mutex_iothread_locked()) {
>> >> +            qemu_mutex_unlock_iothread();
>> >> +        }
>> >>      }
>> >>
>> >>      /* if an exception is pending, we execute it here */
>> >> diff --git a/cpus.c b/cpus.c
>> >> index 860034a794..0ae8f69be5 100644
>> >> --- a/cpus.c
>> >> +++ b/cpus.c
>> >> @@ -1027,8 +1027,6 @@ 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;
>> >>
>> >> @@ -1042,7 +1040,6 @@ 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);
>> >> @@ -1085,10 +1082,6 @@ 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);
>> >>      }
>> >> @@ -1249,9 +1242,11 @@ 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
>> >> @@ -1479,27 +1474,14 @@ 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());
>> >> +    qemu_mutex_lock(&qemu_global_mutex);
>> >>      iothread_locked = true;
>> >>  }
>> >>
>> >>  void qemu_mutex_unlock_iothread(void)
>> >>  {
>> >> +    g_assert(qemu_mutex_iothread_locked());
>> >>      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);
>> >>      }
>> >> -
>> >>      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 865a1e8295..3adf2b1861 100644
>> >> --- a/exec.c
>> >> +++ b/exec.c
>> >> @@ -2134,9 +2134,9 @@ 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);
>> >> @@ -2371,8 +2371,14 @@ 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 7135633863..82a49556af 100644
>> >> --- a/hw/i386/kvmvapic.c
>> >> +++ b/hw/i386/kvmvapic.c
>> >> @@ -457,8 +457,8 @@ 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. */
>> >>          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 c25ee03556..f775aba507 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());
>> >> +
>> >>      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 d171e60b5c..5f93083d4a 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 e465d7ac98..b1e374f3f9 100644
>> >> --- a/hw/ppc/spapr.c
>> >> +++ b/hw/ppc/spapr.c
>> >> @@ -1010,6 +1010,9 @@ static void emulate_spapr_hypercall(PPCVirtualHypervisor *vhyp,
>> >>  {
>> >>      CPUPPCState *env = &cpu->env;
>> >>
>> >> +    /* The TCG path should also be holding the BQL at this point */
>> >> +    g_assert(qemu_mutex_iothread_locked());
>> >> +
>> >>      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 2cf4ecf144..10db89b16a 100644
>> >> --- a/include/qom/cpu.h
>> >> +++ b/include/qom/cpu.h
>> >> @@ -329,6 +329,7 @@ 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 ed8b5aa83e..d61caee867 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 ed87c50cea..58784bcbea 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 47250bcf16..753a69d40d 100644
>> >> --- a/target/arm/helper.c
>> >> +++ b/target/arm/helper.c
>> >> @@ -6769,6 +6769,12 @@ 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 fb366fdc35..5f3e3bdae2 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 8a861cb583..f810259c41 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 */
>> >> @@ -1523,7 +1524,7 @@ 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)
>> >>  {
>> >> @@ -1725,7 +1726,10 @@ 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)
>> >> @@ -1937,6 +1941,7 @@ 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;
>> >> +        }
>> >>      }
>> >>  }
>> >>
>> >> --
>> >> 2.11.0
>> >>
>> >>
>>
>>
>> --
>> Alex Bennée
>>


--
Alex Bennée