KVM: PPC: bookehv: disable MAS register updates early

We need to make sure that no MAS updates happen automatically while we
have the guest MAS registers loaded. So move the disabling code a bit
higher up so that it covers the full time we have guest values in MAS
registers.

The race this patch fixes should never occur, but it makes the code a
bit more logical to do it this way around.

Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Avi Kivity <avi@redhat.com>

1 files changed, 6 insertions, 4 deletions

diff --git a/arch/powerpc/kvm/bookehv_interrupts.S b/arch/powerpc/kvm/bookehv_interrupts.S
index dfa606dedb47..3a1db909947f 100644
--- a/arch/powerpc/kvm/bookehv_interrupts.S
+++ b/arch/powerpc/kvm/bookehv_interrupts.S
@@ -358,6 +358,7 @@ _GLOBAL(kvmppc_resume_host)
         mtspr   SPRN_MAS4, r6
         stw     r5, VCPU_SHARED_MAS7_3+0(r11)
         mtspr   SPRN_MAS6, r8
+        /* Enable MAS register updates via exception */
         mfspr   r3, SPRN_EPCR
         rlwinm  r3, r3, 0, ~SPRN_EPCR_DMIUH
         mtspr   SPRN_EPCR, r3
@@ -515,6 +516,11 @@ lightweight_exit:
         mtspr   SPRN_PID, r3
 
         PPC_LL  r11, VCPU_SHARED(r4)
+        /* Disable MAS register updates via exception */
+        mfspr   r3, SPRN_EPCR
+        oris    r3, r3, SPRN_EPCR_DMIUH@h
+        mtspr   SPRN_EPCR, r3
+        isync
         /* Save host mas4 and mas6 and load guest MAS registers */
         mfspr   r3, SPRN_MAS4
         stw     r3, VCPU_HOST_MAS4(r4)
@@ -538,10 +544,6 @@ lightweight_exit:
         lwz     r5, VCPU_SHARED_MAS7_3+0(r11)
         mtspr   SPRN_MAS6, r3
         mtspr   SPRN_MAS7, r5
-        /* Disable MAS register updates via exception */
-        mfspr   r3, SPRN_EPCR
-        oris    r3, r3, SPRN_EPCR_DMIUH@h
-        mtspr   SPRN_EPCR, r3
 
         /*
          * Host interrupt handlers may have clobbered these guest-readable