target/riscv: Add the force HS exception mode

Add a FORCE_HS_EXCEP mode to the RISC-V virtulisation status. This bit
specifies if an exeption should be taken to HS mode no matter the
current delegation status. This is used when an exeption must be taken
to HS mode, such as when handling interrupts.

Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Palmer Dabbelt <palmerdabbelt@google.com>
Signed-off-by: Palmer Dabbelt <palmerdabbelt@google.com>

3 files changed, 26 insertions, 0 deletions

diff --git a/target/riscv/cpu.h b/target/riscv/cpu.h
index a9cbd85..42720d6 100644
--- a/target/riscv/cpu.h
+++ b/target/riscv/cpu.h
@@ -273,6 +273,8 @@ bool riscv_cpu_exec_interrupt(CPUState *cs, int interrupt_request);
 bool riscv_cpu_fp_enabled(CPURISCVState *env);
 bool riscv_cpu_virt_enabled(CPURISCVState *env);
 void riscv_cpu_set_virt_enabled(CPURISCVState *env, bool enable);
+bool riscv_cpu_force_hs_excep_enabled(CPURISCVState *env);
+void riscv_cpu_set_force_hs_excep(CPURISCVState *env, bool enable);
 int riscv_cpu_mmu_index(CPURISCVState *env, bool ifetch);
 hwaddr riscv_cpu_get_phys_page_debug(CPUState *cpu, vaddr addr);
 void  riscv_cpu_do_unaligned_access(CPUState *cs, vaddr addr,
diff --git a/target/riscv/cpu_bits.h b/target/riscv/cpu_bits.h
index 2cdb0de..ad64797 100644
--- a/target/riscv/cpu_bits.h
+++ b/target/riscv/cpu_bits.h
@@ -432,6 +432,12 @@
 
 /* Virtulisation Register Fields */
 #define VIRT_ONOFF          1
+/* This is used to save state for when we take an exception. If this is set
+ * that means that we want to force a HS level exception (no matter what the
+ * delegation is set to). This will occur for things such as a second level
+ * page table fault.
+ */
+#define FORCE_HS_EXCEP      2
 
 /* RV32 satp CSR field masks */
 #define SATP32_MODE         0x80000000
diff --git a/target/riscv/cpu_helper.c b/target/riscv/cpu_helper.c
index e531116..e36ee7d 100644
--- a/target/riscv/cpu_helper.c
+++ b/target/riscv/cpu_helper.c
@@ -100,6 +100,24 @@ void riscv_cpu_set_virt_enabled(CPURISCVState *env, bool enable)
     env->virt = set_field(env->virt, VIRT_ONOFF, enable);
 }
 
+bool riscv_cpu_force_hs_excep_enabled(CPURISCVState *env)
+{
+    if (!riscv_has_ext(env, RVH)) {
+        return false;
+    }
+
+    return get_field(env->virt, FORCE_HS_EXCEP);
+}
+
+void riscv_cpu_set_force_hs_excep(CPURISCVState *env, bool enable)
+{
+    if (!riscv_has_ext(env, RVH)) {
+        return;
+    }
+
+    env->virt = set_field(env->virt, FORCE_HS_EXCEP, enable);
+}
+
 int riscv_cpu_claim_interrupts(RISCVCPU *cpu, uint32_t interrupts)
 {
     CPURISCVState *env = &cpu->env;