Re: [Qemu-devel] [RFC 5/5] arm: Simplify cycle counter

[Peter Maydell]

On 30 April 2015 at 19:14, Christopher Covington
<address@hidden> wrote:
> Present a system with an instructions per cycle of exactly one.
> This makes it less likely a user will mistake the cycle counter
> values as meaningful and makes calculations involving cycles
> trivial while preserving the necessary property of the cycle
> counter register as monotonically increasing.
>
> Signed-off-by: Christopher Covington <address@hidden>
> ---
>  target-arm/helper.c | 9 +++------
>  1 file changed, 3 insertions(+), 6 deletions(-)
>
> diff --git a/target-arm/helper.c b/target-arm/helper.c
> index 3e6fb0b..a027a19 100644
> --- a/target-arm/helper.c
> +++ b/target-arm/helper.c
> @@ -648,8 +648,7 @@ void pmccntr_sync(CPUARMState *env)
>  {
>      uint64_t temp_ticks;
>
> -    temp_ticks = muldiv64(qemu_clock_get_us(QEMU_CLOCK_VIRTUAL),
> -                          get_ticks_per_sec(), 1000000);
> +    temp_ticks = cpu_get_icount_raw();

Are you really really sure the _raw function is the correct one?
Nowhere else in the codebase calls it except the other wrappers
in cpu.c which provide a sane view of the instruction count...
(I suspect cpu_get_icount_raw() should really be static.)

PS: it would be helpful if you could make sure you include
a cover letter for future patchseries: patchsets without a
cover letter are awkward for my workflow... (A single
standalone patch doesn't need a coverletter.)

thanks
-- PMM