On 2023/4/6 08:43, Alistair Francis wrote:
On Thu, Mar 30, 2023 at 11:59 PM Weiwei Li<liwei...@iscas.ac.cn> wrote:
The MPP will be set to the least-privileged supported mode (U if
U-mode is implemented, else M).
I don't think this is right, the spec in section 8.6.4 says this:
Sorry, I didn't find this section in latest release of both privilege
and un-privilege spec
(draft-20230131-c0b298a: Clarify WFI trapping behavior (#972)).
"MRET then in mstatus/mstatush sets MPV=0, MPP=0,
MIE=MPIE, and MPIE=1"
In section 3.1.6.1, the privilege spec says this:
"An MRET or SRET instruction is used to return from a trap in M-mode or
S-mode respectively.
When executing anxRET instruction, supposingxPP holds the valuey,xIE is
set toxPIE; the
privilege mode is changed toy;xPIE is set to 1; andxPP is set to the
least-privileged supported
mode (U if U-mode is implemented, else M). Ify̸=M,xRET also sets MPRV=0"
And I think PRV_U is an illegal value for MPP if U-mode is not implemented.
Regards,
Weiwei Li
So it should just always be 0 (PRV_U is 0)
Alistair
Signed-off-by: Weiwei Li<liwei...@iscas.ac.cn>
Signed-off-by: Junqiang Wang<wangjunqi...@iscas.ac.cn>
---
target/riscv/op_helper.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/target/riscv/op_helper.c b/target/riscv/op_helper.c
index 84ee018f7d..991f06d98d 100644
--- a/target/riscv/op_helper.c
+++ b/target/riscv/op_helper.c
@@ -339,7 +339,8 @@ target_ulong helper_mret(CPURISCVState *env)
mstatus = set_field(mstatus, MSTATUS_MIE,
get_field(mstatus, MSTATUS_MPIE));
mstatus = set_field(mstatus, MSTATUS_MPIE, 1);
- mstatus = set_field(mstatus, MSTATUS_MPP, PRV_U);
+ mstatus = set_field(mstatus, MSTATUS_MPP,
+ riscv_has_ext(env, RVU) ? PRV_U : PRV_M);
mstatus = set_field(mstatus, MSTATUS_MPV, 0);
if ((env->priv_ver >= PRIV_VERSION_1_12_0) && (prev_priv != PRV_M)) {
mstatus = set_field(mstatus, MSTATUS_MPRV, 0);
--
2.25.1
