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From: Richard Henderson <richard.henderson@linaro.org>
To: "Alex Bennée" <alex.bennee@linaro.org>,
	"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>,
	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 13:01:47 -1000
Message-ID: <d9dc58c7-0dfb-dab5-0ba1-5bc6ddb04e74@linaro.org> (raw)
In-Reply-To: <87a6ssubjs.fsf@linaro.org>

On 1/28/21 8:58 AM, Alex Bennée wrote:
> 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;
>     }
> }

Plausible.  You could possibly test this via gdbstub, as there are not many
other users.  I think it would be of the form:

(gdb) call foo()

where foo is a thumb function.

> #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 */

This function need only handle any state that is "deferred" across goto_tb.
This is almost always simply the pc, e.g.

    if (use_goto_tb(s, dest)) {
        tcg_gen_goto_tb(n);
        gen_set_pc_im(s, dest);
        tcg_gen_exit_tb(s->base.tb, n);

A few targets do a bit more than that, especially vs delayed branches, but ARM
does not.

But there should be no thumb state that ought to be updated here.


r~


  reply index

Thread overview: 44+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-01-28  9:27 [PATCH v14 00/22] i386 cleanup PART 2 Claudio Fontana
2021-01-28  9:27 ` [PATCH v14 01/22] cpu: Introduce TCGCpuOperations struct Claudio Fontana
2021-01-28  9:27 ` [PATCH v14 02/22] target/riscv: remove CONFIG_TCG, as it is always TCG Claudio Fontana
2021-01-28 18:34   ` Alex Bennée
2021-01-28  9:27 ` [PATCH v14 03/22] accel/tcg: split TCG-only code from cpu_exec_realizefn Claudio Fontana
2021-01-28  9:27 ` [PATCH v14 04/22] cpu: Move synchronize_from_tb() to tcg_ops Claudio Fontana
2021-01-28 18:58   ` Alex Bennée
2021-01-28 23:01     ` Richard Henderson [this message]
2021-01-28  9:27 ` [PATCH v14 05/22] cpu: Move cpu_exec_* " Claudio Fontana
2021-01-28  9:27 ` [PATCH v14 06/22] cpu: Move tlb_fill " Claudio Fontana
2021-01-28  9:27 ` [PATCH v14 07/22] cpu: Move debug_excp_handler " Claudio Fontana
2021-01-28  9:28 ` [PATCH v14 08/22] target/arm: do not use cc->do_interrupt for KVM directly Claudio Fontana
2021-01-28  9:28 ` [PATCH v14 09/22] cpu: move cc->do_interrupt to tcg_ops Claudio Fontana
2021-01-28  9:28 ` [PATCH v14 10/22] cpu: move cc->transaction_failed " Claudio Fontana
2021-01-28  9:28 ` [PATCH v14 11/22] cpu: move do_unaligned_access " Claudio Fontana
2021-01-28  9:28 ` [PATCH v14 12/22] physmem: make watchpoint checking code TCG-only Claudio Fontana
2021-01-28 19:09   ` Alex Bennée
2021-01-28  9:28 ` [PATCH v14 13/22] cpu: move adjust_watchpoint_address to tcg_ops Claudio Fontana
2021-01-28  9:28 ` [PATCH v14 14/22] cpu: move debug_check_watchpoint " Claudio Fontana
2021-01-28  9:28 ` [PATCH v14 15/22] cpu: tcg_ops: move to tcg-cpu-ops.h, keep a pointer in CPUClass Claudio Fontana
2021-01-29  0:31   ` Richard Henderson
2021-01-29  9:00     ` Claudio Fontana
2021-01-29 19:19       ` Richard Henderson
2021-01-29 19:36         ` Eduardo Habkost
2021-01-30  9:40           ` Claudio Fontana
2021-02-02 10:01     ` Claudio Fontana
2021-02-02 10:27       ` Claudio Fontana
2021-01-28  9:28 ` [PATCH v14 16/22] accel: extend AccelState and AccelClass to user-mode Claudio Fontana
2021-01-28  9:28 ` [PATCH v14 17/22] accel: replace struct CpusAccel with AccelOpsClass Claudio Fontana
2021-01-28  9:28 ` [PATCH v14 18/22] accel: introduce AccelCPUClass extending CPUClass Claudio Fontana
2021-01-28 13:03   ` Philippe Mathieu-Daudé
2021-01-28 13:22     ` Claudio Fontana
2021-01-28 16:08       ` Alex Bennée
2021-01-28 16:29         ` Philippe Mathieu-Daudé
2021-01-29  0:13           ` Richard Henderson
2021-01-30 10:53             ` Claudio Fontana
2021-01-30 19:01               ` Richard Henderson
2021-02-01  9:15                 ` Alex Bennée
2021-02-01  9:22                   ` Claudio Fontana
2021-01-28  9:28 ` [PATCH v14 19/22] i386: split cpu accelerators from cpu.c, using AccelCPUClass Claudio Fontana
2021-01-28  9:28 ` [PATCH v14 20/22] cpu: call AccelCPUClass::cpu_realizefn in cpu_exec_realizefn Claudio Fontana
2021-01-28  9:28 ` [PATCH v14 21/22] hw/core/cpu: call qemu_init_vcpu in cpu_common_realizefn Claudio Fontana
2021-01-28  9:28 ` [PATCH v14 22/22] accel: introduce new accessor functions Claudio Fontana
2021-01-29  0:22 ` [PATCH v14 00/22] i386 cleanup PART 2 Richard Henderson

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