Re: [PATCH 34/35] exec: push BQL down to cpu->do_interrupt

[David Hildenbrand <david@redhat.com>]

Am 17.09.18 um 18:31 schrieb Emilio G. Cota:
> From: Paolo Bonzini <pbonzini@redhat.com>
> 
> cpu->do_interrupt can now be called with BQL held (from
> cpu->cpu_exec_interrupt) or without (from cpu_handle_exception).
> 
> Only a few targets rely on global device state in cc->do_interrupt;
> add checks to those targets to acquire the BQL if not already held.
> 
> Cc: Aleksandar Markovic <amarkovic@wavecomp.com>
> Cc: Alexander Graf <agraf@suse.de>
> Cc: Anthony Green <green@moxielogic.com>
> Cc: Artyom Tarasenko <atar4qemu@gmail.com>
> Cc: Aurelien Jarno <aurelien@aurel32.net>
> Cc: Christian Borntraeger <borntraeger@de.ibm.com>
> Cc: Chris Wulff <crwulff@gmail.com>
> Cc: Cornelia Huck <cohuck@redhat.com>
> Cc: David Gibson <david@gibson.dropbear.id.au>
> Cc: David Hildenbrand <david@redhat.com>
> Cc: "Edgar E. Iglesias" <edgar.iglesias@gmail.com>
> Cc: Eduardo Habkost <ehabkost@redhat.com>
> Cc: Guan Xuetao <gxt@mprc.pku.edu.cn>
> Cc: James Hogan <jhogan@kernel.org>
> Cc: kvm@vger.kernel.org
> Cc: Laurent Vivier <laurent@vivier.eu>
> Cc: Marcelo Tosatti <mtosatti@redhat.com>
> Cc: Marek Vasut <marex@denx.de>
> Cc: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
> Cc: Michael Walle <michael@walle.cc>
> Cc: Peter Crosthwaite <crosthwaite.peter@gmail.com>
> Cc: Peter Maydell <peter.maydell@linaro.org>
> Cc: qemu-arm@nongnu.org
> Cc: qemu-ppc@nongnu.org
> Cc: qemu-s390x@nongnu.org
> Cc: Richard Henderson <rth@twiddle.net>
> Cc: Stafford Horne <shorne@gmail.com>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> Signed-off-by: Emilio G. Cota <cota@braap.org>
> ---
>  accel/tcg/cpu-exec.c       |  2 --
>  target/arm/helper.c        | 28 ++++++++++++++++++++++++++--
>  target/ppc/excp_helper.c   |  8 +++++++-
>  target/s390x/excp_helper.c | 14 +++++++++++++-
>  target/sh4/helper.c        | 14 +++++++++++++-
>  target/xtensa/helper.c     | 16 ++++++++++++++--
>  6 files changed, 73 insertions(+), 9 deletions(-)
> 
> diff --git a/accel/tcg/cpu-exec.c b/accel/tcg/cpu-exec.c
> index 2383763f9b..b649e3d772 100644
> --- a/accel/tcg/cpu-exec.c
> +++ b/accel/tcg/cpu-exec.c
> @@ -497,9 +497,7 @@ 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 */
> diff --git a/target/arm/helper.c b/target/arm/helper.c
> index 22dbc42305..548278da14 100644
> --- a/target/arm/helper.c
> +++ b/target/arm/helper.c
> @@ -7644,7 +7644,8 @@ gen_invep:
>      return false;
>  }
>  
> -void arm_v7m_cpu_do_interrupt(CPUState *cs)
> +/* call with the BQL held */
> +static void arm_v7m_cpu_do_interrupt_locked(CPUState *cs)
>  {
>      ARMCPU *cpu = ARM_CPU(cs);
>      CPUARMState *env = &cpu->env;
> @@ -7828,6 +7829,17 @@ void arm_v7m_cpu_do_interrupt(CPUState *cs)
>      v7m_exception_taken(cpu, lr, false, ignore_stackfaults);
>  }
>  
> +void arm_v7m_cpu_do_interrupt(CPUState *cs)
> +{
> +    if (qemu_mutex_iothread_locked()) {
> +        arm_v7m_cpu_do_interrupt_locked(cs);
> +    } else {
> +        qemu_mutex_lock_iothread();
> +        arm_v7m_cpu_do_interrupt_locked(cs);
> +        qemu_mutex_unlock_iothread();
> +    }
> +}
> +
>  /* Function used to synchronize QEMU's AArch64 register set with AArch32
>   * register set.  This is necessary when switching between AArch32 and AArch64
>   * execution state.
> @@ -8482,8 +8494,9 @@ static inline bool check_for_semihosting(CPUState *cs)
>   * Do any appropriate logging, handle PSCI calls, and then hand off
>   * to the AArch64-entry or AArch32-entry function depending on the
>   * target exception level's register width.
> + * Call with the BQL held.
>   */
> -void arm_cpu_do_interrupt(CPUState *cs)
> +static void arm_cpu_do_interrupt_locked(CPUState *cs)
>  {
>      ARMCPU *cpu = ARM_CPU(cs);
>      CPUARMState *env = &cpu->env;
> @@ -8534,6 +8547,17 @@ void arm_cpu_do_interrupt(CPUState *cs)
>      }
>  }
>  
> +void arm_cpu_do_interrupt(CPUState *cs)
> +{
> +    if (qemu_mutex_iothread_locked()) {
> +        arm_cpu_do_interrupt_locked(cs);
> +    } else {
> +        qemu_mutex_lock_iothread();
> +        arm_cpu_do_interrupt_locked(cs);
> +        qemu_mutex_unlock_iothread();
> +    }
> +}
> +
>  /* Return the exception level which controls this address translation regime */
>  static inline uint32_t regime_el(CPUARMState *env, ARMMMUIdx mmu_idx)
>  {
> diff --git a/target/ppc/excp_helper.c b/target/ppc/excp_helper.c
> index 70ac10e23b..8b2cc48cad 100644
> --- a/target/ppc/excp_helper.c
> +++ b/target/ppc/excp_helper.c
> @@ -742,7 +742,13 @@ void ppc_cpu_do_interrupt(CPUState *cs)
>      PowerPCCPU *cpu = POWERPC_CPU(cs);
>      CPUPPCState *env = &cpu->env;
>  
> -    powerpc_excp(cpu, env->excp_model, cs->exception_index);
> +    if (qemu_mutex_iothread_locked()) {
> +        powerpc_excp(cpu, env->excp_model, cs->exception_index);
> +    } else {
> +        qemu_mutex_lock_iothread();
> +        powerpc_excp(cpu, env->excp_model, cs->exception_index);
> +        qemu_mutex_unlock_iothread();
> +    }
>  }
>  
>  static void ppc_hw_interrupt(CPUPPCState *env)
> diff --git a/target/s390x/excp_helper.c b/target/s390x/excp_helper.c
> index f2b92d7cbc..931c0103c8 100644
> --- a/target/s390x/excp_helper.c
> +++ b/target/s390x/excp_helper.c
> @@ -378,7 +378,8 @@ static void do_mchk_interrupt(CPUS390XState *env)
>      load_psw(env, mask, addr);
>  }
>  
> -void s390_cpu_do_interrupt(CPUState *cs)
> +/* call with the BQL held */
> +static void s390_cpu_do_interrupt_locked(CPUState *cs)
>  {
>      QEMUS390FLICState *flic = QEMU_S390_FLIC(s390_get_flic());
>      S390CPU *cpu = S390_CPU(cs);
> @@ -457,6 +458,17 @@ try_deliver:
>      }
>  }
>  
> +void s390_cpu_do_interrupt(CPUState *cs)
> +{
> +    if (qemu_mutex_iothread_locked()) {
> +        s390_cpu_do_interrupt_locked(cs);
> +    } else {
> +        qemu_mutex_lock_iothread();
> +        s390_cpu_do_interrupt_locked(cs);
> +        qemu_mutex_unlock_iothread();
> +    }
> +}
> +

Yes, due to floating interrupts we need the iothread lock. This change
looks sane to me from an s390x perspective:

Reviewed-by: David Hildenbrand <david@redhat.com>


-- 

Thanks,

David / dhildenb