Re: [PATCH 2/4] target/arm: Move cortex-m related functions to new file v7m.c

From: Thomas Huth <thuth@redhat.com>
To: Auger Eric <eric.auger@redhat.com>,
	qemu-devel@nongnu.org, Peter Maydell <peter.maydell@linaro.org>
Cc: "Richard Henderson" <richard.henderson@linaro.org>,
	qemu-arm@nongnu.org, "Philippe Mathieu-Daudé" <philmd@redhat.com>
Subject: Re: [PATCH 2/4] target/arm: Move cortex-m related functions to new file v7m.c
Date: Mon, 23 Sep 2019 20:09:08 +0200	[thread overview]
Message-ID: <8585b93b-e239-829b-d634-b89941f27aed@redhat.com> (raw)
In-Reply-To: <bd6efd14-9200-98e2-4f76-dda101f85274@redhat.com>

On 23/09/2019 16.31, Auger Eric wrote:
> Hi Thomas,
> 
> On 9/21/19 5:04 PM, Thomas Huth wrote:
>> We are going to make CONFIG_ARM_V7M optional, so the related cortex-m
>> CPUs should only be created if the switch is enabled. This can best
>> be done if the code resides in a separate file, thus move the related
>> functions to a new file v7m.c which only gets compiled if CONFIG_ARM_V7M
>> is enabled.
>>
>> Signed-off-by: Thomas Huth <thuth@redhat.com>
>> ---
>>  target/arm/Makefile.objs |   1 +
>>  target/arm/cpu.c         | 146 -----------------------------
>>  target/arm/v7m.c         | 193 +++++++++++++++++++++++++++++++++++++++
>>  3 files changed, 194 insertions(+), 146 deletions(-)
>>  create mode 100644 target/arm/v7m.c
[...]
>> diff --git a/target/arm/v7m.c b/target/arm/v7m.c
>> new file mode 100644
>> index 0000000000..505043febe
>> --- /dev/null
>> +++ b/target/arm/v7m.c
>> @@ -0,0 +1,193 @@
>> +/*
>> + * ARM v7m helpers.
>> + *
>> + * This code is licensed under the GNU GPL v2 or later.
>> + *
>> + * SPDX-License-Identifier: GPL-2.0-or-later
>> + */
>> +
>> +#include "qemu/osdep.h"
>> +#include "qemu/qemu-print.h"
>> +#include "qemu-common.h"
>> +#include "target/arm/idau.h"
>> +#include "qemu/module.h"
>> +#include "qapi/error.h"
>> +#include "qapi/visitor.h"
>> +#include "cpu.h"
>> +#include "internals.h"
>> +#include "exec/exec-all.h"
>> +#include "hw/qdev-properties.h"
>> +#if !defined(CONFIG_USER_ONLY)
>> +#include "hw/loader.h"
>> +#include "hw/boards.h"
>> +#endif
>> +#include "sysemu/sysemu.h"
>> +#include "sysemu/tcg.h"
>> +#include "sysemu/hw_accel.h"
>> +#include "disas/capstone.h"
>> +#include "fpu/softfloat.h"
>
> I guess some of those headers are not needed.

Yeah, I just copy-n-pasted from the source file ... I'll check what can
be omitted (if this patch series has a chance at all...)

>> +
>> +#if !defined(CONFIG_USER_ONLY) || !defined(TARGET_AARCH64)
>> +
>> +static bool arm_v7m_cpu_exec_interrupt(CPUState *cs, int interrupt_request)
>> +{
>> +    CPUClass *cc = CPU_GET_CLASS(cs);
>> +    ARMCPU *cpu = ARM_CPU(cs);
>> +    CPUARMState *env = &cpu->env;
>> +    bool ret = false;
>> +
>> +    /*
>> +     * ARMv7-M interrupt masking works differently than -A or -R.
>> +     * There is no FIQ/IRQ distinction. Instead of I and F bits
>> +     * masking FIQ and IRQ interrupts, an exception is taken only
>> +     * if it is higher priority than the current execution priority
>> +     * (which depends on state like BASEPRI, FAULTMASK and the
>> +     * currently active exception).
>> +     */
>> +    if (interrupt_request & CPU_INTERRUPT_HARD
>> +        && (armv7m_nvic_can_take_pending_exception(env->nvic))) {
>
> so what is the status wrt m_helper.c which stays unconditionally
> compiled. m_helper functions seem to called from target/arm/translate.c
> mostly. Have you abandoned the stub idea. It may be confusing to have 2
> different helper files. At least a comment explaining where a new helper
> shall go may be useful.

All the HELPER() functions should definitely stay in m_helper.c. They
are required for linking. Or do you prefer a stub file instead? Then we
could maybe make the whole m_helper.c conditional in the Makefile.objs
instead.

However, there's one thing I currently don't quite understand in this
code (since I'm not an ARM guy, sorry) : There are references to "v8" in
m_helper.c, too. Is that related to a separate CPU type, ie. should the
v8 code also be available when CONFIG_ARM_V7M is disabled? Or can the
code in m_helper.c be disabled completely if CONFIG_ARM_V7M is not set?

 Thomas