Csr访问

昉·星光 （中文论坛）
1

在测试counter的时候，对0x320进行读取访问会报 Instruction access fault，当前mstatus为0x8000000a00007800

2

具体的操作方法？

3

可能是我的mode有问题，具体是在opensbi init后用csr_read去读取0x320

4

You must be in machine mode per The RISC-V Instruction Set Manual, Volume II: Privileged Architecture | Five EmbedDev Mstatus >= 0x1800 should work. Perhaps a sret or mret changed it behind your back?

(Sorry. Only English. Google Translate is amazing.)

根据 The RISC-V Instruction Set Manual, Volume II: Privileged Architecture | Five EmbedDev Mstatus >= 0x1800，您必须处于机器模式。 也许是一个 sret 或 mret 在你背后改变了它？

5

I try read in ecall handler, but it’s fail

csr_read(CSR_MCOUNTINHIBIT);

system_opcode_insn: Failed to access CSR 0x320 from M-mode

current mode is M-mode,and I try enable the mcounteren and mcounteren,it not work

6

标准里写的是

If the mcountinhibit register is not implemented, the implementation behaves as though the register were set to zero.

好像 mcountinhibit 就是没有实现

7

Maybe you are right,I try all others csr is work

8

Supplementary instruction:U74 priv version is privileged specification v1.10, so in opensbi code they skip the CSR Reg.So this topic can be closed