[Qemu-devel] [PATCH] target-i386/kvm.c: Fix the order of FPU registers in xsave

[Asia Slowinska <asia@lastline.com>]

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Stick to the expected 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 <asia@lastline.com>
---
 target-i386/kvm.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/target-i386/kvm.c b/target-i386/kvm.c
index 94024bc..c77fe73 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[HXSAVE_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[HXSAVE_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);
-- 
1.9.1

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