vm_rtc_write
int vm_rtc_write(struct vmctx *ctx, int offset, uint8_t value);
err = vm_rtc_write(ctx, RTC_LMEM_LSB, lomem);
err = vm_rtc_write(ctx, RTC_LMEM_MSB, lomem >> 8);
err = vm_rtc_write(ctx, RTC_HMEM_LSB, himem);
err = vm_rtc_write(ctx, RTC_HMEM_SB, himem >> 8);
err = vm_rtc_write(ctx, RTC_HMEM_MSB, himem >> 16);
error = vm_rtc_write(ctx, rtc_nvram_offset, rtc_nvram_value);