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[Qemu-devel] [BUG/PATCH] Fix i386 SSE status flag corruption

From: Richard Purdie
Subject: [Qemu-devel] [BUG/PATCH] Fix i386 SSE status flag corruption
Date: Mon, 30 Sep 2013 22:20:57 +0100

This is a combination of bug report and patch. I'm not sure if you'll want to 
fix it 
like this but it illustrates the problem and should be easy to fix based on 

When we restore the mxcsr register with FXRSTOR, we need to update the various 
status flags in CPUX86State by calling update_sse_status(). If we don't, we end 
using the status bits from some other context with interesting results.

I used a function prototype since it makes the fix clear, some code 
might be needed ultimately.

Signed-off-by: Richard Purdie <address@hidden>

Index: qemu-1.5.0/target-i386/fpu_helper.c
--- qemu-1.5.0.orig/target-i386/fpu_helper.c    2013-09-30 18:46:39.283377648 
+++ qemu-1.5.0/target-i386/fpu_helper.c 2013-09-30 18:46:56.895377232 +0000
@@ -1149,6 +1149,8 @@
+static void update_sse_status(CPUX86State *env);
 void helper_fxrstor(CPUX86State *env, target_ulong ptr, int data64)
     int i, fpus, fptag, nb_xmm_regs;
@@ -1180,6 +1182,7 @@
     if (env->cr[4] & CR4_OSFXSR_MASK) {
         /* XXX: finish it */
         env->mxcsr = cpu_ldl_data(env, ptr + 0x18);
+        update_sse_status(env);
         /* cpu_ldl_data(env, ptr + 0x1c); */
         if (env->hflags & HF_CS64_MASK) {
             nb_xmm_regs = 16;

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