MIPS: KVM: Fix ASID restoration logic

ASID restoration on guest resume should determine the guest execution
mode based on the guest Status register rather than bit 30 of the guest
PC.

Fix the two places in locore.S that do this, loading the guest status
from the cop0 area. Note, this assembly is specific to the trap &
emulate implementation of KVM, so it doesn't need to check the
supervisor bit as that mode is not implemented in the guest.

Fixes: b680f70fc111 ("KVM/MIPS32: Entry point for trampolining to...")
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Gleb Natapov <gleb@kernel.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
Cc: <stable@vger.kernel.org> # 3.10.x-
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 10 insertions, 6 deletions

diff --git a/arch/mips/kvm/locore.S b/arch/mips/kvm/locore.S
index 7bab3a4e8f7d..7e2210846b8b 100644
--- a/arch/mips/kvm/locore.S
+++ b/arch/mips/kvm/locore.S
@@ -157,9 +157,11 @@ FEXPORT(__kvm_mips_vcpu_run)
 
 FEXPORT(__kvm_mips_load_asid)
         /* Set the ASID for the Guest Kernel */
-        INT_SLL t0, t0, 1       /* with kseg0 @ 0x40000000, kernel */
-                                /* addresses shift to 0x80000000 */
-        bltz    t0, 1f          /* If kernel */
+        PTR_L   t0, VCPU_COP0(k1)
+        LONG_L  t0, COP0_STATUS(t0)
+        andi    t0, KSU_USER | ST0_ERL | ST0_EXL
+        xori    t0, KSU_USER
+        bnez    t0, 1f          /* If kernel */
          INT_ADDIU t1, k1, VCPU_GUEST_KERNEL_ASID  /* (BD)  */
         INT_ADDIU t1, k1, VCPU_GUEST_USER_ASID    /* else user */
 1:
@@ -474,9 +476,11 @@ __kvm_mips_return_to_guest:
         mtc0    t0, CP0_EPC
 
         /* Set the ASID for the Guest Kernel */
-        INT_SLL t0, t0, 1       /* with kseg0 @ 0x40000000, kernel */
-                                /* addresses shift to 0x80000000 */
-        bltz    t0, 1f          /* If kernel */
+        PTR_L   t0, VCPU_COP0(k1)
+        LONG_L  t0, COP0_STATUS(t0)
+        andi    t0, KSU_USER | ST0_ERL | ST0_EXL
+        xori    t0, KSU_USER
+        bnez    t0, 1f          /* If kernel */
          INT_ADDIU t1, k1, VCPU_GUEST_KERNEL_ASID  /* (BD)  */
         INT_ADDIU t1, k1, VCPU_GUEST_USER_ASID    /* else user */
 1: