On 11 June 2018 at 16:26, Igor Mammedov <imamm...@redhat.com> wrote:
> On Fri, 1 Jun 2018 17:03:55 +0100
> Peter Maydell <peter.mayd...@linaro.org> wrote:
>
>> The Cortex-M CPU and its NVIC are two intimately intertwined parts of
>> the same hardware; it is not possible to use one without the other.
>> Unfortunately a lot of our board models don't do any sanity checking
>> on the CPU type the user asks for, so a command line like
>> qemu-system-arm -M versatilepb -cpu cortex-m3
>> will create an M3 without an NVIC, and coredump immediately.
>> In the other direction, trying a non-M-profile CPU in an M-profile
>> board won't blow up, but doesn't do anything useful either:
>> qemu-system-arm -M lm3s6965evb -cpu arm926
>> +#ifndef CONFIG_USER_ONLY
>> + /* The NVIC and M-profile CPU are two halves of a single piece of
>> + * hardware; trying to use one without the other is a command line
>> + * error and will result in segfaults if not caught here.
>> + */
>> + if (arm_feature(env, ARM_FEATURE_M)) {
>> + if (!env->nvic) {
>> + error_setg(errp, "This board cannot be used with Cortex-M
>> CPUs");
> mentioning board in CPU's realize seems a little bit strange,
> maybe something similar to following would be better:
>
> "Cortex-M CPUs require device_foo for working"
I think the text as I have it is of more practical use to the
user, who is clearly not going to be very familiar with how
M-profile systems work if they've run into this error message.
"requires an NVIC" doesn't tell them what's actually wrong;
"this board doesn't work with this CPU" gives them a fighting
chance of understanding that they've given two incompatible
command line options.
thanks
-- PMM
