KVM: PPC: Book3S HV: Make sure we don't re-enter guest without XIVE loaded

This fixes a bug where it is possible to enter a guest on a POWER9
system without having the XIVE (interrupt controller) context loaded.
This can happen because we unload the XIVE context from the CPU
before doing the real-mode handling for machine checks.  After the
real-mode handler runs, it is possible that we re-enter the guest
via a fast path which does not load the XIVE context.

To fix this, we move the unloading of the XIVE context to come after
the real-mode machine check handler is called.

Fixes: 5af50993850a ("KVM: PPC: Book3S HV: Native usage of the XIVE interrupt controller")
Cc: stable@vger.kernel.org # v4.11+
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>

diff --git a/arch/powerpc/kvm/book3s_hv_rmhandlers.S b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
index c8ffd69adfec7af671ab31bd619ccf0a220974bd..76332a3f6c0dcdd5ba8f97d4c23db1dfdace241f 100644 (file)
--- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S
+++ b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
@@ -1423,6 +1423,26 @@ END_FTR_SECTION_IFSET(CPU_FTR_ARCH_300)
        blt     deliver_guest_interrupt
 
 guest_exit_cont:               /* r9 = vcpu, r12 = trap, r13 = paca */
+       /* Save more register state  */
+       mfdar   r6
+       mfdsisr r7
+       std     r6, VCPU_DAR(r9)
+       stw     r7, VCPU_DSISR(r9)
+       /* don't overwrite fault_dar/fault_dsisr if HDSI */
+       cmpwi   r12,BOOK3S_INTERRUPT_H_DATA_STORAGE
+       beq     mc_cont
+       std     r6, VCPU_FAULT_DAR(r9)
+       stw     r7, VCPU_FAULT_DSISR(r9)
+
+       /* See if it is a machine check */
+       cmpwi   r12, BOOK3S_INTERRUPT_MACHINE_CHECK
+       beq     machine_check_realmode
+mc_cont:
+#ifdef CONFIG_KVM_BOOK3S_HV_EXIT_TIMING
+       addi    r3, r9, VCPU_TB_RMEXIT
+       mr      r4, r9
+       bl      kvmhv_accumulate_time
+#endif
 #ifdef CONFIG_KVM_XICS
        /* We are exiting, pull the VP from the XIVE */
        lwz     r0, VCPU_XIVE_PUSHED(r9)
@@ -1460,26 +1480,6 @@ guest_exit_cont:         /* r9 = vcpu, r12 = trap, r13 = paca */
        eieio
 1:
 #endif /* CONFIG_KVM_XICS */
-       /* Save more register state  */
-       mfdar   r6
-       mfdsisr r7
-       std     r6, VCPU_DAR(r9)
-       stw     r7, VCPU_DSISR(r9)
-       /* don't overwrite fault_dar/fault_dsisr if HDSI */
-       cmpwi   r12,BOOK3S_INTERRUPT_H_DATA_STORAGE
-       beq     mc_cont
-       std     r6, VCPU_FAULT_DAR(r9)
-       stw     r7, VCPU_FAULT_DSISR(r9)
-
-       /* See if it is a machine check */
-       cmpwi   r12, BOOK3S_INTERRUPT_MACHINE_CHECK
-       beq     machine_check_realmode
-mc_cont:
-#ifdef CONFIG_KVM_BOOK3S_HV_EXIT_TIMING
-       addi    r3, r9, VCPU_TB_RMEXIT
-       mr      r4, r9
-       bl      kvmhv_accumulate_time
-#endif
 
        mr      r3, r12
        /* Increment exit count, poke other threads to exit */