From: Greg Kurz <gkurz@linux.vnet.ibm.com>

Date: Fri, 15 Jan 2016 16:00:12 +0100

Subject: [PATCH] target-ppc: kvm: fix floating point registers sync on

 little-endian hosts

On VSX capable CPUs, the 32 FP registers are mapped to the high-bits

of the 32 first VSX registers. So if you have:

VSR31 = (uint128) 0x0102030405060708090a0b0c0d0e0f00

then

FPR31 = (uint64) 0x0102030405060708

The kernel stores the VSX registers in the fp_state struct following the

host endian element ordering.

On big-endian:

fp_state.fpr[31][0] = 0x0102030405060708

fp_state.fpr[31][1] = 0x090a0b0c0d0e0f00

On little-endian:

fp_state.fpr[31][0] = 0x090a0b0c0d0e0f00

fp_state.fpr[31][1] = 0x0102030405060708

The KVM_GET_ONE_REG and KVM_SET_ONE_REG ioctls preserve this ordering, but

QEMU considers it as big-endian and always copies element [0] to the

fpr[] array and element [1] to the vsr[] array. This does not work with

little-endian hosts, and you will get:

(qemu) p $f31

0x90a0b0c0d0e0f00

instead of:

(qemu) p $f31

0x102030405060708

This patch fixes the element ordering for little-endian hosts.

Signed-off-by: Greg Kurz <gkurz@linux.vnet.ibm.com>

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

(cherry picked from commit 3a4b791b4c13e02537a5cc572fa3de70bc5f68da)

---

 target-ppc/kvm.c | 12 ++++++++++++

 1 file changed, 12 insertions(+)

diff --git a/target-ppc/kvm.c b/target-ppc/kvm.c

index ac70f08..acd3275 100644

--- a/target-ppc/kvm.c

+++ b/target-ppc/kvm.c

@@ -650,8 +650,13 @@ static int kvm_put_fp(CPUState *cs)

         for (i = 0; i < 32; i++) {

             uint64_t vsr[2];

+#ifdef HOST_WORDS_BIGENDIAN

             vsr[0] = float64_val(env->fpr[i]);

             vsr[1] = env->vsr[i];

+#else

+            vsr[0] = env->vsr[i];

+            vsr[1] = float64_val(env->fpr[i]);

+#endif

             reg.addr = (uintptr_t) &vsr;

             reg.id = vsx ? KVM_REG_PPC_VSR(i) : KVM_REG_PPC_FPR(i);

@@ -721,10 +726,17 @@ static int kvm_get_fp(CPUState *cs)

                         vsx ? "VSR" : "FPR", i, strerror(errno));

                 return ret;

             } else {

+#ifdef HOST_WORDS_BIGENDIAN

                 env->fpr[i] = vsr[0];

                 if (vsx) {

                     env->vsr[i] = vsr[1];

                 }

+#else

+                env->fpr[i] = vsr[1];

+                if (vsx) {

+                    env->vsr[i] = vsr[0];

+                }

+#endif

             }

         }

     }