KVM: PPC: Use get/set for to_svcpu to help preemption

When running the 64-bit Book3s PR code without CONFIG_PREEMPT_NONE, we were
doing a few things wrong, most notably access to PACA fields without making
sure that the pointers stay stable accross the access (preempt_disable()).

This patch moves to_svcpu towards a get/put model which allows us to disable
preemption while accessing the shadow vcpu fields in the PACA. That way we
can run preemptible and everyone's happy!

Reported-by: Jörg Sommer <joerg@alea.gnuu.de>
Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Avi Kivity <avi@redhat.com>

1 files changed, 7 insertions, 1 deletions

diff --git a/arch/powerpc/include/asm/kvm_book3s_64.h b/arch/powerpc/include/asm/kvm_book3s_64.h
index d0ac94f98f9e..2054e4726ba2 100644
--- a/arch/powerpc/include/asm/kvm_book3s_64.h
+++ b/arch/powerpc/include/asm/kvm_book3s_64.h
@@ -21,10 +21,16 @@
 #define __ASM_KVM_BOOK3S_64_H__
 
 #ifdef CONFIG_KVM_BOOK3S_PR
-static inline struct kvmppc_book3s_shadow_vcpu *to_svcpu(struct kvm_vcpu *vcpu)
+static inline struct kvmppc_book3s_shadow_vcpu *svcpu_get(struct kvm_vcpu *vcpu)
 {
+        preempt_disable();
         return &get_paca()->shadow_vcpu;
 }
+
+static inline void svcpu_put(struct kvmppc_book3s_shadow_vcpu *svcpu)
+{
+        preempt_enable();
+}
 #endif
 
 #define SPAPR_TCE_SHIFT         12