[PATCH v4 3/6] KVM: arm64: nv: Add nested revmap broken tracepoint

[Wei-Lin Chang]

Add a tracepoint to track when a nested reverse map becomes broken. This
makes it easier to detect NV performance degradation caused by full
shadow stage-2 unmaps.

Signed-off-by: Wei-Lin Chang <weilin.chang at arm.com>
---
 arch/arm64/kvm/nested.c    |  7 ++++++-
 arch/arm64/kvm/trace_arm.h | 27 +++++++++++++++++++++++++++
 2 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/kvm/nested.c b/arch/arm64/kvm/nested.c
index 065823e415ce..22f8a1daca93 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"
 
 struct vncr_tlb {
 	/* The guest's VNCR_EL2 */
@@ -916,8 +917,12 @@ void kvm_record_nested_revmap(gpa_t canonical_ipa, struct kvm_s2_mmu *mmu,
 
 	mas_set_range(&mas_rmap, canonical_ipa, canonical_ipa_end);
 	if (mas_store_gfp(&mas_rmap, xa_mk_value(new_entry),
-			  GFP_NOWAIT | __GFP_ACCOUNT))
+			  GFP_NOWAIT | __GFP_ACCOUNT)) {
+		trace_kvm_nested_revmap_broken(mmu - mmu->arch->nested_mmus,
+					       canonical_ipa, canonical_ipa_end,
+					       nested_ipa, new_entry);
 		mmu->nested_revmap_broken = true;
+	}
 unlock:
 	mtree_unlock(revmap_mt);
 }
diff --git a/arch/arm64/kvm/trace_arm.h b/arch/arm64/kvm/trace_arm.h
index 9c60f6465c78..0db90068ff63 100644
--- a/arch/arm64/kvm/trace_arm.h
+++ b/arch/arm64/kvm/trace_arm.h
@@ -415,6 +415,33 @@ TRACE_EVENT(kvm_forward_sysreg_trap,
 		      sys_reg_Op2(__entry->sysreg))
 );
 
+TRACE_EVENT(kvm_nested_revmap_broken,
+	    TP_PROTO(int mmu_idx, unsigned long canonical_ipa,
+		     unsigned long canonical_ipa_end, unsigned long nested_ipa,
+		     unsigned long revmap_entry),
+	    TP_ARGS(mmu_idx, canonical_ipa, canonical_ipa_end, nested_ipa, revmap_entry),
+
+	    TP_STRUCT__entry(
+		__field(int,			mmu_idx)
+		__field(unsigned long,		canonical_ipa)
+		__field(unsigned long,		nested_ipa)
+		__field(size_t,			size)
+		__field(unsigned long,		revmap_entry)
+	    ),
+
+	    TP_fast_assign(
+		__entry->mmu_idx = mmu_idx;
+		__entry->canonical_ipa = canonical_ipa;
+		__entry->nested_ipa = nested_ipa;
+		__entry->size = canonical_ipa_end - canonical_ipa + 1;
+		__entry->revmap_entry = revmap_entry;
+	    ),
+
+	    TP_printk("mmu idx: %d, cipa: 0x%016lx, nipa: 0x%016lx, size: 0x%016lx, entry: %016lx",
+		      __entry->mmu_idx, __entry->canonical_ipa, __entry->nested_ipa,
+		      __entry->size, __entry->revmap_entry)
+);
+
 #endif /* _TRACE_ARM_ARM64_KVM_H */
 
 #undef TRACE_INCLUDE_PATH
-- 
2.43.0