Re: [Qemu-arm] [PATCH v3] aspeed_scu: Implement RNG register

[Philippe Mathieu-Daudé]

On 05/29/2018 01:19 AM, Joel Stanley wrote:
> The ASPEED SoCs contain a single register that returns random data when
> read. This models that register so that guests can use it.
> 
> The random number data register has a corresponding control register,
> however it returns data regardless of the state of the enabled bit, so
> the model follows this behaviour.
> 
> Reviewed-by: Cédric Le Goater <address@hidden>
> Signed-off-by: Joel Stanley <address@hidden>

Reviewed-by: Philippe Mathieu-Daudé <address@hidden>

> ---
> v2:
>  - Remove call to qcrypto_random_init as this is done in main()
> v3:
>  - Add Cédric's reviewed-by
>  - Add a comment about why we don't check for the rng enable bit
> ---
>  hw/misc/aspeed_scu.c | 19 +++++++++++++++++++
>  1 file changed, 19 insertions(+)
> 
> diff --git a/hw/misc/aspeed_scu.c b/hw/misc/aspeed_scu.c
> index 5e6d5744eeca..96db052389cc 100644
> --- a/hw/misc/aspeed_scu.c
> +++ b/hw/misc/aspeed_scu.c
> @@ -16,6 +16,7 @@
>  #include "qapi/visitor.h"
>  #include "qemu/bitops.h"
>  #include "qemu/log.h"
> +#include "crypto/random.h"
>  #include "trace.h"
>  
>  #define TO_REG(offset) ((offset) >> 2)
> @@ -154,6 +155,18 @@ static const uint32_t 
> ast2500_a1_resets[ASPEED_SCU_NR_REGS] = {
>       [BMC_DEV_ID]      = 0x00002402U
>  };
>  
> +static uint32_t aspeed_scu_get_random(void)
> +{
> +    Error *err = NULL;
> +    uint32_t num;
> +
> +    if (qcrypto_random_bytes((uint8_t *)&num, sizeof(num), &err)) {
> +        error_report_err(err);
> +    }
> +
> +    return num;
> +}
> +
>  static uint64_t aspeed_scu_read(void *opaque, hwaddr offset, unsigned size)
>  {
>      AspeedSCUState *s = ASPEED_SCU(opaque);
> @@ -167,6 +180,12 @@ static uint64_t aspeed_scu_read(void *opaque, hwaddr 
> offset, unsigned size)
>      }
>  
>      switch (reg) {
> +    case RNG_DATA:
> +        /* On hardware, RNG_DATA works regardless of
> +         * the state of the enable bit in RNG_CTRL
> +         */
> +        s->regs[RNG_DATA] = aspeed_scu_get_random();
> +        break;
>      case WAKEUP_EN:
>          qemu_log_mask(LOG_GUEST_ERROR,
>                        "%s: Read of write-only offset 0x%" HWADDR_PRIx "\n",
>