[PATCH 34/89] KVM: arm64: Don't access kvm_arm_hyp_percpu_base at EL1

[Will Deacon]

From: Quentin Perret <qperret at google.com>

The host KVM PMU code can currently index kvm_arm_hyp_percpu_base[]
through this_cpu_ptr_hyp_sym(), but will not actually dereference that
pointer when protected KVM is enabled. In preparation for making
kvm_arm_hyp_percpu_base[] unaccessible to the host, let's make sure the
indexing in hyp per-cpu pages is also done after the static key check to
avoid spurious accesses to EL2-private data from EL1.

Signed-off-by: Quentin Perret <qperret at google.com>
---
 arch/arm64/kvm/pmu.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/arch/arm64/kvm/pmu.c b/arch/arm64/kvm/pmu.c
index 03a6c1f4a09a..a8878fd8b696 100644
--- a/arch/arm64/kvm/pmu.c
+++ b/arch/arm64/kvm/pmu.c
@@ -31,9 +31,13 @@ static bool kvm_pmu_switch_needed(struct perf_event_attr *attr)
  */
 void kvm_set_pmu_events(u32 set, struct perf_event_attr *attr)
 {
-	struct kvm_host_data *ctx = this_cpu_ptr_hyp_sym(kvm_host_data);
+	struct kvm_host_data *ctx;
 
-	if (!kvm_arm_support_pmu_v3() || !ctx || !kvm_pmu_switch_needed(attr))
+	if (!kvm_arm_support_pmu_v3())
+		return;
+
+	ctx = this_cpu_ptr_hyp_sym(kvm_host_data);
+	if (!ctx || !kvm_pmu_switch_needed(attr))
 		return;
 
 	if (!attr->exclude_host)
@@ -47,9 +51,13 @@ void kvm_set_pmu_events(u32 set, struct perf_event_attr *attr)
  */
 void kvm_clr_pmu_events(u32 clr)
 {
-	struct kvm_host_data *ctx = this_cpu_ptr_hyp_sym(kvm_host_data);
+	struct kvm_host_data *ctx;
+
+	if (!kvm_arm_support_pmu_v3())
+		return;
 
-	if (!kvm_arm_support_pmu_v3() || !ctx)
+	ctx = this_cpu_ptr_hyp_sym(kvm_host_data);
+	if (!ctx)
 		return;
 
 	ctx->pmu_events.events_host &= ~clr;
-- 
2.36.1.124.g0e6072fb45-goog