The code to check whether rd > MIPS_CP0_DESAVE is dead code, since
MIPS_CP0_DESAVE = 31 and rd is already masked with 0x1f. Remove it.
Signed-off-by: NJames Hogan <james.hogan@imgtec.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Gleb Natapov <gleb@kernel.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Sanjay Lal <sanjayl@kymasys.com>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

The ability to read hardware registers from userland with the RDHWR
instruction should depend upon the corresponding bit of the HWREna
register being set, otherwise a reserved instruction exception should be
generated.

However KVM's current emulation ignores the guest's HWREna and always
emulates RDHWR instructions even if the guest OS has disallowed them.

Therefore rework the RDHWR emulation code to check for privilege or the
corresponding bit in the guest HWREna bit. Also remove the #if 0 case
for the UserLocal register. I presume it was there for debug purposes
but it seems unnecessary now that the guest can control whether it
causes a guest exception.
Signed-off-by: NJames Hogan <james.hogan@imgtec.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Gleb Natapov <gleb@kernel.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Sanjay Lal <sanjayl@kymasys.com>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

Previously a reserved instruction exception while in guest code would
cause a KVM internal error if kvm_mips_handle_ri() didn't recognise the
instruction (including a RDHWR from an unrecognised hardware register).

However the guest OS should really have the opportunity to catch the
exception so that it can take the appropriate actions such as sending a
SIGILL to the guest user process or emulating the instruction itself.

Therefore in these cases emulate a guest RI exception and only return
EMULATE_FAIL if that fails, being careful to revert the PC first in case
the exception occurred in a branch delay slot in which case the PC will
already point to the branch target.

Also turn the printk messages relating to these cases into kvm_debug
messages so that they aren't usually visible.

This allows crashme to run in the guest without killing the entire VM.
Signed-off-by: NJames Hogan <james.hogan@imgtec.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Gleb Natapov <gleb@kernel.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Sanjay Lal <sanjayl@kymasys.com>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
Cc: stable@vger.kernel.org
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>

This reverts commit d532f3d2.

The original commit has several problems:

1) Doesn't work with 64-bit kernels.

2) Calls TLBMISS_HANDLER_SETUP() before the code is generated.

3) Calls TLBMISS_HANDLER_SETUP() twice in per_cpu_trap_init() when
   only one call is needed.

[ralf@linux-mips.org: Also revert the bits of the ASID patch which were
hidden in the KVM merge.]
Signed-off-by: NDavid Daney <david.daney@cavium.com>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Cc: "Steven J. Hill" <Steven.Hill@imgtec.com>
Cc: David Daney <david.daney@cavium.com>
Patchwork: https://patchwork.linux-mips.org/patch/5242/Signed-off-by: NRalf Baechle <ralf@linux-mips.org>

- The Guest kernel is run in UM and privileged instructions cause a trap.
- If the instruction causing the trap is in a branch delay slot, the branch
  needs to be emulated to figure out the PC @ which the guest will resume
  execution.
Signed-off-by: NSanjay Lal <sanjayl@kymasys.com>
Cc: kvm@vger.kernel.org
Cc: linux-mips@linux-mips.org
Signed-off-by: NRalf Baechle <ralf@linux-mips.org>