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Re: [Qemu-devel] [PATCH v2 1/2] cpu: Provide a proper prototype for targ
From: |
Laszlo Ersek |
Subject: |
Re: [Qemu-devel] [PATCH v2 1/2] cpu: Provide a proper prototype for target_words_bigendian() in a header |
Date: |
Fri, 5 Oct 2018 15:20:30 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 |
On 10/05/18 15:01, Thomas Huth wrote:
> We've got three places already that provide a prototype for this
> function in a .c file - that's ugly. Let's provide a proper prototype
> in a header instead, with a proper description why this function should
> not be used in most cases.
>
> Signed-off-by: Thomas Huth <address@hidden>
> ---
> NB: I've tried to replace the "utterly broken" comment with something
> better, as suggested by Laszlo... not sure whether I've really got the
> message right here, so feel free to provide some better wording if you
> like!
>
> exec.c | 5 -----
> hw/virtio/virtio.c | 1 -
> include/qom/cpu.h | 11 +++++++++++
> qom/cpu.c | 1 -
> 4 files changed, 11 insertions(+), 7 deletions(-)
>
> diff --git a/exec.c b/exec.c
> index d0821e6..5d99ef5 100644
> --- a/exec.c
> +++ b/exec.c
> @@ -3906,11 +3906,6 @@ int qemu_target_page_bits_min(void)
> }
> #endif
>
> -/*
> - * A helper function for the _utterly broken_ virtio device model to find
> out if
> - * it's running on a big endian machine. Don't do this at home kids!
> - */
> -bool target_words_bigendian(void);
> bool target_words_bigendian(void)
> {
> #if defined(TARGET_WORDS_BIGENDIAN)
> diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
> index 94f5c8e..4e61944 100644
> --- a/hw/virtio/virtio.c
> +++ b/hw/virtio/virtio.c
> @@ -1169,7 +1169,6 @@ int virtio_set_status(VirtIODevice *vdev, uint8_t val)
> return 0;
> }
>
> -bool target_words_bigendian(void);
> static enum virtio_device_endian virtio_default_endian(void)
> {
> if (target_words_bigendian()) {
> diff --git a/include/qom/cpu.h b/include/qom/cpu.h
> index dc130cd..6d35c37 100644
> --- a/include/qom/cpu.h
> +++ b/include/qom/cpu.h
> @@ -1085,6 +1085,17 @@ void cpu_exec_initfn(CPUState *cpu);
> void cpu_exec_realizefn(CPUState *cpu, Error **errp);
> void cpu_exec_unrealizefn(CPUState *cpu);
>
> +/**
> + * target_words_bigendian:
> + * Returns true if the (default) endianness of the target is big endian,
> + * false otherwise. Note that in target-specifc code, you can use
> + * TARGET_WORDS_BIGENDIAN directly instead. On the other hand, common
> + * code should normally never need to know about the endianness of the
> + * target, so please do *not* use this function unless you know very well
> + * what you are doing!
> + */
> +bool target_words_bigendian(void);
> +
> #ifdef NEED_CPU_H
>
> #ifdef CONFIG_SOFTMMU
> diff --git a/qom/cpu.c b/qom/cpu.c
> index 92599f3..f774654 100644
> --- a/qom/cpu.c
> +++ b/qom/cpu.c
> @@ -194,7 +194,6 @@ static bool cpu_common_debug_check_watchpoint(CPUState
> *cpu, CPUWatchpoint *wp)
> return true;
> }
>
> -bool target_words_bigendian(void);
> static bool cpu_common_virtio_is_big_endian(CPUState *cpu)
> {
> return target_words_bigendian();
>
This makes sense to me. First I wasn't convinced, because I didn't
immediately get "target-specifc code". However, after looking at the 2nd
patch, I think I understand better (= the obj-XXX vs. common-obj-XXX
distinction). I also think that distinction is clear to any practicing
QEMU developers.
So, for what it's worth (which is admittedly not too much), for the series:
Reviewed-by: Laszlo Ersek <address@hidden>
Thanks
Laszlo