[Qemu-devel] [PATCH v2] target-i386: update fp status fix

[Pavel Dovgalyuk <Pavel.Dovgaluk@ispras.ru>]

This patch introduces cpu_set_fpuc() function, which changes fpuc field
of the CPU state and calls update_fp_status() function.
These calls update status of softfloat library and prevent bugs caused
by non-coherent rounding settings of the FPU and softfloat.

v2 changes:
 * Added missed calls and intoduced setter function (as suggested by TeLeMan)

Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>

Signed-off-by: Pavel Dovgalyuk <pavel.dovgaluk@ispras.ru>
---
 target-i386/cpu.c        |    2 +-
 target-i386/cpu.h        |    2 ++
 target-i386/fpu_helper.c |   21 +++++++++++++--------
 target-i386/gdbstub.c    |    2 +-
 target-i386/machine.c    |    2 +-
 5 files changed, 18 insertions(+), 11 deletions(-)

diff --git a/target-i386/cpu.c b/target-i386/cpu.c
index 217500c..9f48b1c 100644
--- a/target-i386/cpu.c
+++ b/target-i386/cpu.c
@@ -2572,7 +2572,7 @@ static void x86_cpu_reset(CPUState *s)
     for (i = 0; i < 8; i++) {
         env->fptags[i] = 1;
     }
-    env->fpuc = 0x37f;
+    cpu_set_fpuc(env, 0x37f);
 
     env->mxcsr = 0x1f80;
     env->xstate_bv = XSTATE_FP | XSTATE_SSE;
diff --git a/target-i386/cpu.h b/target-i386/cpu.h
index e634d83..6ab8eca 100644
--- a/target-i386/cpu.h
+++ b/target-i386/cpu.h
@@ -1249,6 +1249,7 @@ void QEMU_NORETURN raise_interrupt(CPUX86State *nenv, int intno, int is_int,
 /* cc_helper.c */
 extern const uint8_t parity_table[256];
 uint32_t cpu_cc_compute_all(CPUX86State *env1, int op);
+void update_fp_status(CPUX86State *env);
 
 static inline uint32_t cpu_compute_eflags(CPUX86State *env)
 {
@@ -1284,6 +1285,7 @@ static inline void cpu_load_efer(CPUX86State *env, uint64_t val)
 
 /* fpu_helper.c */
 void cpu_set_mxcsr(CPUX86State *env, uint32_t val);
+void cpu_set_fpuc(CPUX86State *env, uint16_t val);
 
 /* svm_helper.c */
 void cpu_svm_check_intercept_param(CPUX86State *env1, uint32_t type,
diff --git a/target-i386/fpu_helper.c b/target-i386/fpu_helper.c
index 1b2900d..1d4eee3 100644
--- a/target-i386/fpu_helper.c
+++ b/target-i386/fpu_helper.c
@@ -537,7 +537,7 @@ uint32_t helper_fnstcw(CPUX86State *env)
     return env->fpuc;
 }
 
-static void update_fp_status(CPUX86State *env)
+void update_fp_status(CPUX86State *env)
 {
     int rnd_type;
 
@@ -575,8 +575,7 @@ static void update_fp_status(CPUX86State *env)
 
 void helper_fldcw(CPUX86State *env, uint32_t val)
 {
-    env->fpuc = val;
-    update_fp_status(env);
+    cpu_set_fpuc(env, val);
 }
 
 void helper_fclex(CPUX86State *env)
@@ -595,7 +594,7 @@ void helper_fninit(CPUX86State *env)
 {
     env->fpus = 0;
     env->fpstt = 0;
-    env->fpuc = 0x37f;
+    cpu_set_fpuc(env, 0x37f);
     env->fptags[0] = 1;
     env->fptags[1] = 1;
     env->fptags[2] = 1;
@@ -1013,11 +1012,11 @@ void helper_fldenv(CPUX86State *env, target_ulong ptr, int data32)
     int i, fpus, fptag;
 
     if (data32) {
-        env->fpuc = cpu_lduw_data(env, ptr);
+        cpu_set_fpuc(env, cpu_lduw_data(env, ptr));
         fpus = cpu_lduw_data(env, ptr + 4);
         fptag = cpu_lduw_data(env, ptr + 8);
     } else {
-        env->fpuc = cpu_lduw_data(env, ptr);
+        cpu_set_fpuc(env, cpu_lduw_data(env, ptr));
         fpus = cpu_lduw_data(env, ptr + 2);
         fptag = cpu_lduw_data(env, ptr + 4);
     }
@@ -1046,7 +1045,7 @@ void helper_fsave(CPUX86State *env, target_ulong ptr, int data32)
     /* fninit */
     env->fpus = 0;
     env->fpstt = 0;
-    env->fpuc = 0x37f;
+    cpu_set_fpuc(env, 0x37f);
     env->fptags[0] = 1;
     env->fptags[1] = 1;
     env->fptags[2] = 1;
@@ -1157,7 +1156,7 @@ void helper_fxrstor(CPUX86State *env, target_ulong ptr, int data64)
         raise_exception(env, EXCP0D_GPF);
     }
 
-    env->fpuc = cpu_lduw_data(env, ptr);
+    cpu_set_fpuc(env, cpu_lduw_data(env, ptr));
     fpus = cpu_lduw_data(env, ptr + 2);
     fptag = cpu_lduw_data(env, ptr + 4);
     env->fpstt = (fpus >> 11) & 7;
@@ -1257,6 +1256,12 @@ void cpu_set_mxcsr(CPUX86State *env, uint32_t mxcsr)
     set_flush_to_zero((mxcsr & SSE_FZ) ? 1 : 0, &env->fp_status);
 }
 
+void cpu_set_fpuc(CPUX86State *env, uint16_t val)
+{
+    env->fpuc = val;
+    update_fp_status(env);
+}
+
 void helper_ldmxcsr(CPUX86State *env, uint32_t val)
 {
     cpu_set_mxcsr(env, val);
diff --git a/target-i386/gdbstub.c b/target-i386/gdbstub.c
index 19fe9ad..ff99cfb 100644
--- a/target-i386/gdbstub.c
+++ b/target-i386/gdbstub.c
@@ -203,7 +203,7 @@ int x86_cpu_gdb_write_register(CPUState *cs, uint8_t *mem_buf, int n)
             return x86_cpu_gdb_load_seg(cpu, R_GS, mem_buf);
 
         case IDX_FP_REGS + 8:
-            env->fpuc = ldl_p(mem_buf);
+            cpu_set_fpuc(env, ldl_p(mem_buf));
             return 4;
         case IDX_FP_REGS + 9:
             tmp = ldl_p(mem_buf);
diff --git a/target-i386/machine.c b/target-i386/machine.c
index 16d2f6a..2922c97 100644
--- a/target-i386/machine.c
+++ b/target-i386/machine.c
@@ -315,13 +315,13 @@ static int cpu_post_load(void *opaque, int version_id)
     env->hflags &= ~HF_CPL_MASK;
     env->hflags |= (env->segs[R_SS].flags >> DESC_DPL_SHIFT) & HF_CPL_MASK;
 
-    /* XXX: restore FPU round state */
     env->fpstt = (env->fpus_vmstate >> 11) & 7;
     env->fpus = env->fpus_vmstate & ~0x3800;
     env->fptag_vmstate ^= 0xff;
     for(i = 0; i < 8; i++) {
         env->fptags[i] = (env->fptag_vmstate >> i) & 1;
     }
+    update_fp_status(env);
 
     cpu_breakpoint_remove_all(cs, BP_CPU);
     cpu_watchpoint_remove_all(cs, BP_CPU);