On 05.06.14 19:33, Aneesh Kumar K.V wrote:
Alexander Graf <agraf@xxxxxxx> writes:
On 05.06.14 17:50, Aneesh Kumar K.V wrote:
Alexander Graf <agraf@xxxxxxx> writes:
On 05.06.14 14:08, Aneesh Kumar K.V wrote:
virtual time base register is a per VM, per cpu register that needs
to be saved and restored on vm exit and entry. Writing to VTB is not
allowed in the privileged mode.
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxxxxxxx>
.......
break;
diff --git a/arch/powerpc/kvm/book3s_emulate.c b/arch/powerpc/kvm/book3s_emulate.c
index 3565e775b61b..1bb16a59dcbc 100644
--- a/arch/powerpc/kvm/book3s_emulate.c
+++ b/arch/powerpc/kvm/book3s_emulate.c
@@ -577,6 +577,9 @@ int kvmppc_core_emulate_mfspr_pr(struct kvm_vcpu *vcpu, int sprn, ulong *spr_val
*/
*spr_val = vcpu->arch.spurr;
break;
+ case SPRN_VTB:
+ *spr_val = vcpu->arch.vtb;
Doesn't this mean that vtb can be the same 2 when the guest reads it 2
times in a row without getting preempted?
But a mfspr will result in VM exit and that would make sure we
update vcpu->arch.vtb with the correct value.
We only call kvmppc_core_vcpu_put_pr() when we context switch away from
KVM, so it won't be updated, no?
kvmppc_copy_from_svcpu is also called from VM exit path (book3s_interrupt.S)
... where it will run into this code path:
/*
* Maybe we were already preempted and synced the svcpu from
* our preempt notifiers. Don't bother touching this svcpu then.
*/
if (!svcpu->in_use)
goto out;
Alex
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