target-i386/kvm.c: Fix the order of FPU registers in xsave

Commit Message

Asia Slowinska Feb. 10, 2016, 2:39 p.m. UTC

Many thanks for the reply. I'm sorry for the typo in the previous patch.
Below comes a new one.

Best regards,
asia

Stick to the right order of the FPU registers in xsave (as specified in the
Intel manual.)  Otherwise, instructions loading the FPU state don't set it
up
correctly.

To set up FPU, software needs to provide a buffer of 80 bytes storing 8 FPU
registers. They are organized in a stack. FPU assumes that the first field
of
the buffer is ST0, then ST1, and so on. QEMU maintains a circular buffer.
When
preparing these 80 bytes for KVM, QEMU just uses memcpy instead of copying
the
elements in a proper order.

Signed-off-by: Asia Slowinska <[e-mail]>
---
 target-i386/kvm.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

Patch

diff --git a/target-i386/kvm.c b/target-i386/kvm.c
index 94024bc..a9e6c75 100644
--- a/target-i386/kvm.c
+++ b/target-i386/kvm.c
@@ -1325,8 +1325,10 @@  static int kvm_put_xsave(X86CPU *cpu)
     xsave->region[XSAVE_FTW_FOP] = (uint32_t)(env->fpop << 16) + twd;
     memcpy(&xsave->region[XSAVE_CWD_RIP], &env->fpip, sizeof(env->fpip));
     memcpy(&xsave->region[XSAVE_CWD_RDP], &env->fpdp, sizeof(env->fpdp));
-    memcpy(&xsave->region[XSAVE_ST_SPACE], env->fpregs,
-            sizeof env->fpregs);
+    for (i = 0; i < 8; i++) {
+        memcpy(&xsave_region[XSAVE_ST_SPACE + i * 4],
+            &env->fpregs[(env->fpstt + i) & 7], 16);
+    }
     xsave->region[XSAVE_MXCSR] = env->mxcsr;
     *(uint64_t *)&xsave->region[XSAVE_XSTATE_BV] = env->xstate_bv;
     memcpy(&xsave->region[XSAVE_BNDREGS], env->bnd_regs,
@@ -1745,8 +1747,10 @@  static int kvm_get_xsave(X86CPU *cpu)
     memcpy(&env->fpip, &xsave->region[XSAVE_CWD_RIP], sizeof(env->fpip));
     memcpy(&env->fpdp, &xsave->region[XSAVE_CWD_RDP], sizeof(env->fpdp));
     env->mxcsr = xsave->region[XSAVE_MXCSR];
-    memcpy(env->fpregs, &xsave->region[XSAVE_ST_SPACE],
-            sizeof env->fpregs);
+    for (i = 0; i < 8; i++) {
+        memcpy(&env->fpregs[(env->fpstt + i) & 7],
+            &xsave_region[XSAVE_ST_SPACE + i * 4], 16);
+    }
     env->xstate_bv = *(uint64_t *)&xsave->region[XSAVE_XSTATE_BV];
     memcpy(env->bnd_regs, &xsave->region[XSAVE_BNDREGS],
             sizeof env->bnd_regs);