[PATCH v2 28/28] KVM: arm64: Add tracepoints for S2 page table walk

[Oliver Upton <oupton@kernel.org>]

MMU walk steps are a useful tidbit of information for KVM hackers. As
these events are far closer to modelling CPU architecture than exposing
KVM internals it clears the bar for adding tracepoints.

Signed-off-by: Oliver Upton <oupton@kernel.org>
---
 arch/arm64/include/asm/kvm_nested.h |  6 ++++
 arch/arm64/kvm/nested.c             | 14 ++++-----
 arch/arm64/kvm/trace_arm.h          | 47 +++++++++++++++++++++++++++++
 3 files changed, 59 insertions(+), 8 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_nested.h b/arch/arm64/include/asm/kvm_nested.h
index 341604b619cc..65dc411188cb 100644
--- a/arch/arm64/include/asm/kvm_nested.h
+++ b/arch/arm64/include/asm/kvm_nested.h
@@ -128,6 +128,12 @@ struct kvm_walk_access {
 	bool	write;
 };
 
+struct s2_walk_step {
+	u64		desc_pa;
+	u64		desc;
+	int		level;
+};
+
 extern int kvm_walk_nested_s2(struct kvm_vcpu *vcpu, struct kvm_walk_access *access,
 			      struct kvm_s2_trans *result);
 extern int kvm_s2_handle_perm_fault(struct kvm_vcpu *vcpu,
diff --git a/arch/arm64/kvm/nested.c b/arch/arm64/kvm/nested.c
index 0c468235f123..a04ab2200d36 100644
--- a/arch/arm64/kvm/nested.c
+++ b/arch/arm64/kvm/nested.c
@@ -17,6 +17,7 @@
 #include <asm/sysreg.h>
 
 #include "sys_regs.h"
+#include "trace.h"
 #include "vgic/vgic.h"
 
 struct vncr_tlb {
@@ -155,12 +156,6 @@ struct s2_walk_info {
 	bool		haft;
 };
 
-struct s2_walk_step {
-	u64		desc_pa;
-	u64		desc;
-	int		level;
-};
-
 static u32 compute_fsc(int level, u32 fsc)
 {
 	return fsc | (level & 0x3);
@@ -279,10 +274,10 @@ static int handle_desc_update(struct kvm_vcpu *vcpu, struct s2_walk_info *wi,
 			      struct s2_walk_step *ws, struct kvm_s2_trans *out,
 			      struct kvm_walk_access *access)
 {
-	u64 old, new;
+	u64 old, old_cpu, new;
 	int ret;
 
-	old = new = ws->desc;
+	old = old_cpu = new = ws->desc;
 
 	if (should_set_access_flag(wi, ws, access))
 		new |= KVM_PTE_LEAF_ATTR_LO_S2_AF;
@@ -307,6 +302,7 @@ static int handle_desc_update(struct kvm_vcpu *vcpu, struct s2_walk_info *wi,
 	if (ret == -EAGAIN)
 		return ret;
 	if (!ret) {
+		trace_kvm_s2_desc_update(ws, access->ia, old_cpu);
 		out->desc = ws->desc;
 		out->dirty = out->desc & KVM_PTE_LEAF_ATTR_LO_S2_S2AP_W;
 		return 0;
@@ -425,6 +421,8 @@ static int walk_nested_s2_pgd(struct kvm_vcpu *vcpu, struct kvm_walk_access *acc
 			return ret;
 		}
 
+		trace_kvm_s2_walk_step(&ws, access->ia);
+
 		/* Check for valid descriptor at this point */
 		if (!(ws.desc & KVM_PTE_VALID)) {
 			out->esr = compute_fsc(ws.level, ESR_ELx_FSC_FAULT);
diff --git a/arch/arm64/kvm/trace_arm.h b/arch/arm64/kvm/trace_arm.h
index 9fe9b57f6fa8..0bf1a0be2636 100644
--- a/arch/arm64/kvm/trace_arm.h
+++ b/arch/arm64/kvm/trace_arm.h
@@ -467,6 +467,53 @@ TRACE_EVENT(kvm_s1_desc_update,
 		      __entry->pa, __entry->level)
 );
 
+TRACE_EVENT(kvm_s2_walk_step,
+	    TP_PROTO(struct s2_walk_step *ws, u64 ia),
+	    TP_ARGS(ws, ia),
+
+	    TP_STRUCT__entry(
+		__field(u64,	ia)
+		__field(u64,	desc)
+		__field(u64,	pa)
+		__field(int,	level)
+	    ),
+
+	    TP_fast_assign(
+		__entry->ia	= ia;
+		__entry->desc	= ws->desc;
+		__entry->pa	= ws->desc_pa;
+		__entry->level	= ws->level;
+	    ),
+
+	    TP_printk("ia: 0x%llx desc: 0x%llx pa: 0x%llx level: %d",
+		      __entry->ia, __entry->desc, __entry->pa, __entry->level)
+);
+
+TRACE_EVENT(kvm_s2_desc_update,
+	    TP_PROTO(struct s2_walk_step *ws, u64 ia, u64 old),
+	    TP_ARGS(ws, ia, old),
+
+	    TP_STRUCT__entry(
+		__field(u64,	ia)
+		__field(u64,	new)
+		__field(u64,	old)
+		__field(u64,	pa)
+		__field(int,	level)
+	    ),
+
+	    TP_fast_assign(
+		__entry->ia	= ia;
+		__entry->new	= ws->desc;
+		__entry->old	= old;
+		__entry->pa	= ws->desc_pa;
+		__entry->level	= ws->level;
+	    ),
+
+	    TP_printk("ia: 0x%llx new: 0x%llx old: 0x%llx pa: 0x%llx level: %d",
+		      __entry->ia, __entry->new, __entry->old, __entry->pa,
+		      __entry->level)
+);
+
 #endif /* _TRACE_ARM_ARM64_KVM_H */
 
 #undef TRACE_INCLUDE_PATH
-- 
2.47.3