On 03/04/2017 14:45, Alex Bennée wrote:
> Outside of the vCPU thread icount time will only be tracked against
> timers_state.qemu_icount. We no longer credit cycles until they have
> completed the run. Inside the vCPU thread we adjust for passage of
> time by looking at how many have run so far. This is only valid inside
> the vCPU thread while it is running.
>
> Signed-off-by: Alex Bennée <alex.ben...@linaro.org>
I suspect icount_budget and icount_extra could be merged into one, but
not for 2.9. For now this looks nice!
Paolo
> ---
> cpus.c | 27 +++++++++++++++++++++------
> include/qom/cpu.h | 1 +
> 2 files changed, 22 insertions(+), 6 deletions(-)
>
> diff --git a/cpus.c b/cpus.c
> index 87638a75d2..3d18374b0e 100644
> --- a/cpus.c
> +++ b/cpus.c
> @@ -223,6 +223,15 @@ void qemu_tcg_configure(QemuOpts *opts, Error **errp)
> }
> }
>
> +/* The current number of executed instructions is based on what we
> + * originally budgeted minus the current state of the decrementing
> + * icount counters in extra/u16.low.
> + */
> +static int64_t cpu_get_icount_executed(CPUState *cpu)
> +{
> + return cpu->icount_budget - (cpu->icount_decr.u16.low +
> cpu->icount_extra);
> +}
> +
> int64_t cpu_get_icount_raw(void)
> {
> int64_t icount;
> @@ -234,7 +243,8 @@ int64_t cpu_get_icount_raw(void)
> fprintf(stderr, "Bad icount read\n");
> exit(1);
> }
> - icount -= (cpu->icount_decr.u16.low + cpu->icount_extra);
> + /* Take into account what has run */
> + icount += cpu_get_icount_executed(cpu);
> }
> return icount;
> }
> @@ -1195,7 +1205,10 @@ static void prepare_icount_for_run(CPUState *cpu)
>
> count = tcg_get_icount_limit();
>
> - timers_state.qemu_icount += count;
> + /* To calculate what we have executed so far we need to know
> + * what we originally budgeted to run this cycle */
> + cpu->icount_budget = count;
> +
> decr = (count > 0xffff) ? 0xffff : count;
> count -= decr;
> cpu->icount_decr.u16.low = decr;
> @@ -1206,16 +1219,18 @@ static void prepare_icount_for_run(CPUState *cpu)
> static void process_icount_data(CPUState *cpu)
> {
> if (use_icount) {
> - /* Fold pending instructions back into the
> - instruction counter, and clear the interrupt flag. */
> - timers_state.qemu_icount -= (cpu->icount_decr.u16.low
> - + cpu->icount_extra);
> + /* Account for executed instructions */
> + timers_state.qemu_icount += cpu_get_icount_executed(cpu);
>
> /* We must be under BQL here as cpu_exit can tweak
> icount_decr.u32 */
> g_assert(qemu_mutex_iothread_locked());
> +
> + /* Reset the counters */
> cpu->icount_decr.u32 = 0;
> cpu->icount_extra = 0;
> + cpu->icount_budget = 0;
> +
> replay_account_executed_instructions();
> }
> }
> diff --git a/include/qom/cpu.h b/include/qom/cpu.h
> index c3292efe1c..5d10359c8f 100644
> --- a/include/qom/cpu.h
> +++ b/include/qom/cpu.h
> @@ -332,6 +332,7 @@ struct CPUState {
> /* updates protected by BQL */
> uint32_t interrupt_request;
> int singlestep_enabled;
> + int64_t icount_budget;
> int64_t icount_extra;
> sigjmp_buf jmp_env;
>
>
