Re: [RFC PATCH 2/2] hw/sd: skip double power-up in sd_vmstate_pre_load()

["Philippe Mathieu-Daudé" <philmd@linaro.org>]

+David / Juan / Peter for migration and timers.

On 20/1/23 13:01, Daniel Henrique Barboza wrote:
> At this moment any migration with the RISC-V sifive_u machine
> fails with the following error:
> 
> qemu-system-riscv64: ../hw/sd/sd.c:297: sd_ocr_powerup: Assertion
> `!FIELD_EX32(sd->ocr, OCR, CARD_POWER_UP)' failed.
> 
> The assert was introduced by dd26eb43337a ("hw/sd: model a power-up
> delay, as a workaround for an EDK2 bug"). It introduced a delayed timer
> of 0.5ms to power up the card after the first ACMD41 command. The assert
> prevents the card from being turned on twice.
> 
> When migrating a machine that uses a sd card, e.g. RISC-V sifive_u, the
> card is turned on during machine_init() in both source and destination
> hosts. When the migration stream finishes in the destination, the
> pre_load() hook will attempt to turn on the card before loading its
> vmstate. The assert() is always going to hit because the card was
> already on.
> 
> Change sd_vmstate_pre_load() to check first if the sd card is turned on
> before executing a sd_ocr_powerup() and triggering the assert.
> 
> Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
> ---
>   hw/sd/sd.c | 12 ++++++++++--
>   1 file changed, 10 insertions(+), 2 deletions(-)
> 
> diff --git a/hw/sd/sd.c b/hw/sd/sd.c
> index bd88c1a8f0..4add719643 100644
> --- a/hw/sd/sd.c
> +++ b/hw/sd/sd.c
> @@ -664,11 +664,19 @@ static int sd_vmstate_pre_load(void *opaque)
>   {
>       SDState *sd = opaque;
>   
> -    /* If the OCR state is not included (prior versions, or not
> +    /*
> +     * If the OCR state is not included (prior versions, or not
>        * needed), then the OCR must be set as powered up. If the OCR state
>        * is included, this will be replaced by the state restore.
> +     *
> +     * However, there's a chance that the board will powerup the SD
> +     * before reaching INMIGRATE state in the destination host.
> +     * Powering up the SD again in this case will cause an assert
> +     * inside sd_ocr_powerup(). Skip sd_ocr_powerup() in this case.
>        */
> -    sd_ocr_powerup(sd);
> +    if (!sd_card_powered_up(sd)) {
> +        sd_ocr_powerup(sd);
> +    }
>   
>       return 0;
>   }