[PATCH v15 01/21] target/riscv: expose *envcfg csr and priv to qemu-user as well

[Deepak Gupta <debug@rivosinc.com>]

Execution environment config CSR controlling user env and current
privilege state shouldn't be limited to qemu-system only. *envcfg
CSRs control enabling of features in next lesser mode. In some cases
bits *envcfg CSR can be lit up by kernel as part of kernel policy or
software (user app) can choose to opt-in by issuing a system call
(e.g. prctl). In case of qemu-user, it should be no different because
qemu is providing underlying execution environment facility and thus
either should provide some default value in *envcfg CSRs or react to
system calls (prctls) initiated from application. priv is set to PRV_U
and menvcfg/senvcfg set to 0 for qemu-user on reest.

`henvcfg` has been left for qemu-system only because it is not expected
that someone will use qemu-user where application is expected to have
hypervisor underneath which is controlling its execution environment. If
such a need arises then `henvcfg` could be exposed as well.

Relevant discussion:
https://lore.kernel.org/all/CAKmqyKOTVWPFep2msTQVdUmJErkH+bqCcKEQ4hAnyDFPdWKe0Q@mail.gmail.com/

Signed-off-by: Deepak Gupta <debug@rivosinc.com>
Suggested-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
---
 target/riscv/cpu.c | 5 +++++
 target/riscv/cpu.h | 9 +++++----
 2 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
index 658bdb4ae1..24ca0bfcaa 100644
--- a/target/riscv/cpu.c
+++ b/target/riscv/cpu.c
@@ -1003,7 +1003,12 @@ static void riscv_cpu_reset_hold(Object *obj, ResetType type)
     }
 
     pmp_unlock_entries(env);
+#else
+    env->priv = PRV_U;
+    env->senvcfg = 0;
+    env->menvcfg = 0;
 #endif
+
     env->xl = riscv_cpu_mxl(env);
     riscv_cpu_update_mask(env);
     cs->exception_index = RISCV_EXCP_NONE;
diff --git a/target/riscv/cpu.h b/target/riscv/cpu.h
index 1619c3acb6..2623f6cf75 100644
--- a/target/riscv/cpu.h
+++ b/target/riscv/cpu.h
@@ -234,8 +234,12 @@ struct CPUArchState {
     uint32_t elf_flags;
 #endif
 
-#ifndef CONFIG_USER_ONLY
     target_ulong priv;
+    /* CSRs for execution environment configuration */
+    uint64_t menvcfg;
+    target_ulong senvcfg;
+
+#ifndef CONFIG_USER_ONLY
     /* This contains QEMU specific information about the virt state. */
     bool virt_enabled;
     target_ulong geilen;
@@ -445,12 +449,9 @@ struct CPUArchState {
     target_ulong upmmask;
     target_ulong upmbase;
 
-    /* CSRs for execution environment configuration */
-    uint64_t menvcfg;
     uint64_t mstateen[SMSTATEEN_MAX_COUNT];
     uint64_t hstateen[SMSTATEEN_MAX_COUNT];
     uint64_t sstateen[SMSTATEEN_MAX_COUNT];
-    target_ulong senvcfg;
     uint64_t henvcfg;
 #endif
     target_ulong cur_pmmask;
-- 
2.45.0