target/riscv: Create function to test if FP is enabled

Let's create a function that tests if floating point support is
enabled. We can then protect all floating point operations based on if
they are enabled.

This patch so far doesn't change anything, it's just preparing for the
Hypervisor support for floating point operations.

Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Christophe de Dinechin <dinechin@redhat.com>
Signed-off-by: Palmer Dabbelt <palmer@sifive.com>

3 files changed, 26 insertions, 10 deletions

diff --git a/target/riscv/cpu.h b/target/riscv/cpu.h
index 18d91d0..16efe8c 100644
--- a/target/riscv/cpu.h
+++ b/target/riscv/cpu.h
@@ -255,6 +255,7 @@ void riscv_cpu_do_interrupt(CPUState *cpu);
 int riscv_cpu_gdb_read_register(CPUState *cpu, uint8_t *buf, int reg);
 int riscv_cpu_gdb_write_register(CPUState *cpu, uint8_t *buf, int reg);
 bool riscv_cpu_exec_interrupt(CPUState *cs, int interrupt_request);
+bool riscv_cpu_fp_enabled(CPURISCVState *env);
 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,
@@ -298,7 +299,10 @@ static inline void cpu_get_tb_cpu_state(CPURISCVState *env, target_ulong *pc,
 #ifdef CONFIG_USER_ONLY
     *flags = TB_FLAGS_MSTATUS_FS;
 #else
-    *flags = cpu_mmu_index(env, 0) | (env->mstatus & MSTATUS_FS);
+    *flags = cpu_mmu_index(env, 0);
+    if (riscv_cpu_fp_enabled(env)) {
+        *flags |= env->mstatus & MSTATUS_FS;
+    }
 #endif
 }
 
diff --git a/target/riscv/cpu_helper.c b/target/riscv/cpu_helper.c
index e32b612..96373b6 100644
--- a/target/riscv/cpu_helper.c
+++ b/target/riscv/cpu_helper.c
@@ -71,6 +71,16 @@ bool riscv_cpu_exec_interrupt(CPUState *cs, int interrupt_request)
 
 #if !defined(CONFIG_USER_ONLY)
 
+/* Return true is floating point support is currently enabled */
+bool riscv_cpu_fp_enabled(CPURISCVState *env)
+{
+    if (env->mstatus & MSTATUS_FS) {
+        return true;
+    }
+
+    return false;
+}
+
 int riscv_cpu_claim_interrupts(RISCVCPU *cpu, uint32_t interrupts)
 {
     CPURISCVState *env = &cpu->env;
diff --git a/target/riscv/csr.c b/target/riscv/csr.c
index e0d4586..2789215 100644
--- a/target/riscv/csr.c
+++ b/target/riscv/csr.c
@@ -46,7 +46,7 @@ void riscv_set_csr_ops(int csrno, riscv_csr_operations *ops)
 static int fs(CPURISCVState *env, int csrno)
 {
 #if !defined(CONFIG_USER_ONLY)
-    if (!env->debugger && !(env->mstatus & MSTATUS_FS)) {
+    if (!env->debugger && !riscv_cpu_fp_enabled(env)) {
         return -1;
     }
 #endif
@@ -108,7 +108,7 @@ static int pmp(CPURISCVState *env, int csrno)
 static int read_fflags(CPURISCVState *env, int csrno, target_ulong *val)
 {
 #if !defined(CONFIG_USER_ONLY)
-    if (!env->debugger && !(env->mstatus & MSTATUS_FS)) {
+    if (!env->debugger && !riscv_cpu_fp_enabled(env)) {
         return -1;
     }
 #endif
@@ -119,7 +119,7 @@ static int read_fflags(CPURISCVState *env, int csrno, target_ulong *val)
 static int write_fflags(CPURISCVState *env, int csrno, target_ulong val)
 {
 #if !defined(CONFIG_USER_ONLY)
-    if (!env->debugger && !(env->mstatus & MSTATUS_FS)) {
+    if (!env->debugger && !riscv_cpu_fp_enabled(env)) {
         return -1;
     }
     env->mstatus |= MSTATUS_FS;
@@ -131,7 +131,7 @@ static int write_fflags(CPURISCVState *env, int csrno, target_ulong val)
 static int read_frm(CPURISCVState *env, int csrno, target_ulong *val)
 {
 #if !defined(CONFIG_USER_ONLY)
-    if (!env->debugger && !(env->mstatus & MSTATUS_FS)) {
+    if (!env->debugger && !riscv_cpu_fp_enabled(env)) {
         return -1;
     }
 #endif
@@ -142,7 +142,7 @@ static int read_frm(CPURISCVState *env, int csrno, target_ulong *val)
 static int write_frm(CPURISCVState *env, int csrno, target_ulong val)
 {
 #if !defined(CONFIG_USER_ONLY)
-    if (!env->debugger && !(env->mstatus & MSTATUS_FS)) {
+    if (!env->debugger && !riscv_cpu_fp_enabled(env)) {
         return -1;
     }
     env->mstatus |= MSTATUS_FS;
@@ -154,7 +154,7 @@ static int write_frm(CPURISCVState *env, int csrno, target_ulong val)
 static int read_fcsr(CPURISCVState *env, int csrno, target_ulong *val)
 {
 #if !defined(CONFIG_USER_ONLY)
-    if (!env->debugger && !(env->mstatus & MSTATUS_FS)) {
+    if (!env->debugger && !riscv_cpu_fp_enabled(env)) {
         return -1;
     }
 #endif
@@ -166,7 +166,7 @@ static int read_fcsr(CPURISCVState *env, int csrno, target_ulong *val)
 static int write_fcsr(CPURISCVState *env, int csrno, target_ulong val)
 {
 #if !defined(CONFIG_USER_ONLY)
-    if (!env->debugger && !(env->mstatus & MSTATUS_FS)) {
+    if (!env->debugger && !riscv_cpu_fp_enabled(env)) {
         return -1;
     }
     env->mstatus |= MSTATUS_FS;
@@ -307,6 +307,7 @@ static int write_mstatus(CPURISCVState *env, int csrno, target_ulong val)
 {
     target_ulong mstatus = env->mstatus;
     target_ulong mask = 0;
+    int dirty;
 
     /* flush tlb on mstatus fields that affect VM */
     if (env->priv_ver <= PRIV_VERSION_1_09_1) {
@@ -340,8 +341,9 @@ static int write_mstatus(CPURISCVState *env, int csrno, target_ulong val)
 
     mstatus = (mstatus & ~mask) | (val & mask);
 
-    int dirty = ((mstatus & MSTATUS_FS) == MSTATUS_FS) |
-                ((mstatus & MSTATUS_XS) == MSTATUS_XS);
+    dirty = (riscv_cpu_fp_enabled(env) &&
+             ((mstatus & MSTATUS_FS) == MSTATUS_FS)) |
+            ((mstatus & MSTATUS_XS) == MSTATUS_XS);
     mstatus = set_field(mstatus, MSTATUS_SD, dirty);
     env->mstatus = mstatus;