设备初始化

紧接_start_warm，接下来将正式进入C阶段，随机选择满足条件的hart执行clodboot，其余的hart执行warmboot，上篇博文已经详细分析了coolboot的详细过程了，下面就着重对比coolboot分析下warmboot的具体行为。

sbi_init函数

这个函数传入的参数为sbi_scratch结构体，也就是在前面的汇编阶段初始化的scratch空间，CSR_MSCRATCH存储着起始地址。

• 首先需要判断启动模式
• 随机选择满足条件的hart执行clodboot，其余的hart执行warmboot
  注意：Opensbi中的coolboot和warmboot不是传统意义上的冷启动和热启动，而是完全初始化和部分初始化的意思

/*** Initialize OpenSBI library for current HART and jump to next* booting stage.** The function expects following:* 1. The 'mscratch' CSR is pointing to sbi_scratch of current HART* 2. Stack pointer (SP) is setup for current HART* 3. Interrupts are disabled in MSTATUS CSR* 4. All interrupts are disabled in MIE CSR** @param scratch pointer to sbi_scratch of current HART*/
void __noreturn sbi_init(struct sbi_scratch *scratch)
{bool next_mode_supported	= FALSE;bool coldboot			= FALSE;u32 hartid			= current_hartid();const struct sbi_platform *plat = sbi_platform_ptr(scratch);if ((SBI_HARTMASK_MAX_BITS <= hartid) ||sbi_platform_hart_invalid(plat, hartid))sbi_hart_hang();switch (scratch->next_mode) {case PRV_M:next_mode_supported = TRUE;break;case PRV_S:if (misa_extension('S'))next_mode_supported = TRUE;break;case PRV_U: