Re: [PATCH v14 04/22] cpu: Move synchronize_from_tb() to tcg_ops

From: "Alex Bennée" <alex.bennee@linaro.org>
To: Claudio Fontana <cfontana@suse.de>
Cc: "Laurent Vivier" <lvivier@redhat.com>,
	"Peter Maydell" <peter.maydell@linaro.org>,
	"Thomas Huth" <thuth@redhat.com>,
	"Eduardo Habkost" <ehabkost@redhat.com>,
	"Richard Henderson" <richard.henderson@linaro.org>,
	qemu-devel@nongnu.org, "Roman Bolshakov" <r.bolshakov@yadro.com>,
	"Alistair Francis" <alistair.francis@wdc.com>,
	"Paolo Bonzini" <pbonzini@redhat.com>,
	"Philippe Mathieu-Daudé" <philmd@redhat.com>
Subject: Re: [PATCH v14 04/22] cpu: Move synchronize_from_tb() to tcg_ops
Date: Thu, 28 Jan 2021 18:58:03 +0000	[thread overview]
Message-ID: <87a6ssubjs.fsf@linaro.org> (raw)
In-Reply-To: <20210128092814.8676-5-cfontana@suse.de>

Claudio Fontana <cfontana@suse.de> writes:

> From: Eduardo Habkost <ehabkost@redhat.com>
>
> Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
>
> [claudio: wrapped in CONFIG_TCG]
> Signed-off-by: Claudio Fontana <cfontana@suse.de>
> ---
>  include/hw/core/cpu.h     | 20 +++++++++++---------
>  accel/tcg/cpu-exec.c      |  4 ++--
>  target/arm/cpu.c          |  4 +++-
>  target/avr/cpu.c          |  2 +-
>  target/hppa/cpu.c         |  2 +-
>  target/i386/tcg/tcg-cpu.c |  2 +-
>  target/microblaze/cpu.c   |  2 +-
>  target/mips/cpu.c         |  4 +++-
>  target/riscv/cpu.c        |  2 +-
>  target/rx/cpu.c           |  2 +-
>  target/sh4/cpu.c          |  2 +-
>  target/sparc/cpu.c        |  2 +-
>  target/tricore/cpu.c      |  2 +-
>  13 files changed, 28 insertions(+), 22 deletions(-)
>
> diff --git a/include/hw/core/cpu.h b/include/hw/core/cpu.h
> index 96fdca39d2..b3c1bb77eb 100644
> --- a/include/hw/core/cpu.h
> +++ b/include/hw/core/cpu.h
> @@ -87,6 +87,17 @@ typedef struct TcgCpuOperations {
>       * Called when the first CPU is realized.
>       */
>      void (*initialize)(void);
> +    /**
> +     * @synchronize_from_tb: Synchronize state from a TCG #TranslationBlock
> +     *
> +     * This is called when we abandon execution of a TB before
> +     * starting it, and must set all parts of the CPU state which
> +     * the previous TB in the chain may not have updated. This
> +     * will need to do more. If this hook is not implemented then
> +     * the default is to call @set_pc(tb->pc).
> +     */

Possibly re-word a little more?

  ...TB in the chain may not have updated. By default when no hook is
  defined a call is made to @set_pc(tb->pc). If more state needs to be
  restored the front-end must provide a hook function and restore all the
  state there.

> diff --git a/target/arm/cpu.c b/target/arm/cpu.c
> index fa4d4ba4eb..140cb33f07 100644
> --- a/target/arm/cpu.c
> +++ b/target/arm/cpu.c
> @@ -54,6 +54,7 @@ static void arm_cpu_set_pc(CPUState *cs, vaddr value)
>      }
>  }
>  
> +#ifdef CONFIG_TCG
>  static void arm_cpu_synchronize_from_tb(CPUState *cs,
>                                          const TranslationBlock *tb)
>  {
> @@ -70,6 +71,7 @@ static void arm_cpu_synchronize_from_tb(CPUState *cs,
>          env->regs[15] = tb->pc;
>      }
>  }
> +#endif /* CONFIG_TCG */

Looking at the function here I wonder if we should be worried about the
thumb state? Peter?

static void arm_cpu_set_pc(CPUState *cs, vaddr value)
{
    ARMCPU *cpu = ARM_CPU(cs);
    CPUARMState *env = &cpu->env;

    if (is_a64(env)) {
        env->pc = value;
        env->thumb = 0;
    } else {
        env->regs[15] = value & ~1;
        env->thumb = value & 1;
    }
}

#ifdef CONFIG_TCG
void arm_cpu_synchronize_from_tb(CPUState *cs,
                                 const TranslationBlock *tb)
{
    ARMCPU *cpu = ARM_CPU(cs);
    CPUARMState *env = &cpu->env;

    /*
     * It's OK to look at env for the current mode here, because it's
     * never possible for an AArch64 TB to chain to an AArch32 TB.
     */
    if (is_a64(env)) {
        env->pc = tb->pc;
    } else {
        env->regs[15] = tb->pc;
    }
}
#endif /* CONFIG_TCG */

Otherwise:

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>

-- 
Alex Bennée