[PATCH v2 1/3] KVM: arm64: Add a stage2 page fault counter for kvm_stat

[Yoan Picchi]

This counter is meant to detect stage 2 page fault exits. This is meant to
measure how much those page fault influence the performance (by comparing
this number of exits to some other exit causes).
For now this counter is generic, but some more granularity is planned in
the next commits so that one know how much of the page fault are for memory
allocation, or for mmio for instance. The idea being that one using this
counter can get a better idea of what is trigerring those exits to try to
fix it.

Signed-off-by: Yoan Picchi <yoan.picchi at arm.com>
---
 arch/arm64/include/asm/kvm_host.h | 1 +
 arch/arm64/kvm/guest.c            | 1 +
 arch/arm64/kvm/mmu.c              | 2 ++
 3 files changed, 4 insertions(+)

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 3d10e6527..02891ce94 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -561,6 +561,7 @@ struct kvm_vcpu_stat {
 	u64 wfi_exit_stat;
 	u64 mmio_exit_user;
 	u64 mmio_exit_kernel;
+	u64 stage2_abort_exit;
 	u64 exits;
 };
 
diff --git a/arch/arm64/kvm/guest.c b/arch/arm64/kvm/guest.c
index 9bbd30e62..82a4b6275 100644
--- a/arch/arm64/kvm/guest.c
+++ b/arch/arm64/kvm/guest.c
@@ -38,6 +38,7 @@ struct kvm_stats_debugfs_item debugfs_entries[] = {
 	VCPU_STAT("wfi_exit_stat", wfi_exit_stat),
 	VCPU_STAT("mmio_exit_user", mmio_exit_user),
 	VCPU_STAT("mmio_exit_kernel", mmio_exit_kernel),
+	VCPU_STAT("stage2_abort_exit", stage2_abort_exit),
 	VCPU_STAT("exits", exits),
 	VCPU_STAT("halt_poll_success_ns", halt_poll_success_ns),
 	VCPU_STAT("halt_poll_fail_ns", halt_poll_fail_ns),
diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index 77cb2d28f..c3527ccf6 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -966,6 +966,7 @@ int kvm_handle_guest_abort(struct kvm_vcpu *vcpu)
 	fault_ipa = kvm_vcpu_get_fault_ipa(vcpu);
 	is_iabt = kvm_vcpu_trap_is_iabt(vcpu);
 
+
 	/* Synchronous External Abort? */
 	if (kvm_vcpu_abt_issea(vcpu)) {
 		/*
@@ -980,6 +981,7 @@ int kvm_handle_guest_abort(struct kvm_vcpu *vcpu)
 
 	trace_kvm_guest_fault(*vcpu_pc(vcpu), kvm_vcpu_get_esr(vcpu),
 			      kvm_vcpu_get_hfar(vcpu), fault_ipa);
+	vcpu->stat.stage2_abort_exit++;
 
 	/* Check the stage-2 fault is trans. fault or write fault */
 	if (fault_status != FSC_FAULT && fault_status != FSC_PERM &&
-- 
2.17.1