Re: [PATCH v2 2/2] hw/riscv: Provide rdtime callback for TCG in CLINT emulation

[Palmer Dabbelt]

On Wed, 22 Jan 2020 11:30:36 GMT (+0000), Anup Patel wrote:
> This patch extends CLINT emulation to provide rdtime callback for
> TCG. This rdtime callback will be called wheneven TIME CSRs are
> read in privileged modes.
>
> Signed-off-by: Anup Patel <address@hidden>
> Reviewed-by: Alistair Francis <address@hidden>
> ---
>  hw/riscv/sifive_clint.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/hw/riscv/sifive_clint.c b/hw/riscv/sifive_clint.c
> index e5a8f75cee..805503dc27 100644
> --- a/hw/riscv/sifive_clint.c
> +++ b/hw/riscv/sifive_clint.c
> @@ -236,6 +236,7 @@ DeviceState *sifive_clint_create(hwaddr addr, hwaddr size, 
> uint32_t num_harts,
>          if (!env) {
>              continue;
>          }
> +        riscv_cpu_set_rdtime_fn(env, cpu_riscv_read_rtc);
>          env->timer = timer_new_ns(QEMU_CLOCK_VIRTUAL,
>                                    &sifive_clint_timer_cb, cpu);
>          env->timecmp = 0;
> --
> 2.17.1

Can you make this optional?  Ideally via a command-line argument, but at a
minimum as via the board configuration files.  As it stands this will enable
the direct rdtime implemnetation everywhere, and while that's sensible for the
virt board I'd prefer to avoid changing the behavior of the sifive_u board in
ways that differ from the hardware when that's easy.