MIPS KVM uses different ASIDs for guest execution than for the host.
The host ASID is saved on the stack when entering the guest with
__kvm_mips_vcpu_run(), and restored again before returning back to the
caller (exit to userland).
- This does not take into account that pre-emption may have taken place
during that time, which may have started a new ASID cycle and resulted
in that process' ASID being invalidated and reused.
- This does not take into account that the process may have migrated to
a different CPU during that time, with a different ASID assignment
since they are managed per-CPU.
- It is actually redundant, since the host ASID will be restored
correctly by kvm_arch_vcpu_put(), which is called almost immediately
after kvm_arch_vcpu_ioctl_run() returns.
Therefore drop this code from locore.S
Signed-off-by: James Hogan <james.hogan@xxxxxxxxxx>
Cc: Ralf Baechle <ralf@xxxxxxxxxxxxxx>
Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Cc: Radim Krčmář <rkrcmar@xxxxxxxxxx>
Cc: linux-mips@xxxxxxxxxxxxxx
Cc: kvm@xxxxxxxxxxxxxxx
---
arch/mips/kvm/locore.S | 12 ------------
1 file changed, 12 deletions(-)
diff --git a/arch/mips/kvm/locore.S b/arch/mips/kvm/locore.S
index 81687ab1b523..c24facc85357 100644
--- a/arch/mips/kvm/locore.S
+++ b/arch/mips/kvm/locore.S
@@ -32,7 +32,6 @@
EXPORT(x);
/* Overload, Danger Will Robinson!! */
-#define PT_HOST_ASID PT_BVADDR
#define PT_HOST_USERLOCAL PT_EPC
#define CP0_DDATA_LO $28,3
@@ -104,11 +103,6 @@ FEXPORT(__kvm_mips_vcpu_run)
mfc0 v0, CP0_STATUS
LONG_S v0, PT_STATUS(k1)
- /* Save host ASID, shove it into the BVADDR location */
- mfc0 v1, CP0_ENTRYHI
- andi v1, 0xff
- LONG_S v1, PT_HOST_ASID(k1)
-
/* Save DDATA_LO, will be used to store pointer to vcpu */
mfc0 v1, CP0_DDATA_LO
LONG_S v1, PT_HOST_USERLOCAL(k1)
@@ -551,12 +545,6 @@ __kvm_mips_return_to_host:
LONG_L k0, PT_HOST_USERLOCAL(k1)
mtc0 k0, CP0_DDATA_LO
- /* Restore host ASID */
- LONG_L k0, PT_HOST_ASID(sp)
- andi k0, 0xff
- mtc0 k0,CP0_ENTRYHI
- ehb
-
/* Load context saved on the host stack */
LONG_L $0, PT_R0(k1)
LONG_L $1, PT_R1(k1)
--
2.4.10
