[PATCH 2/3] KVM: nVMX: Add a new VCPU statistic to show if VCPU is running nested guest

[Krish Sadhukhan <krish.sadhukhan@xxxxxxxxxx>]

Add the following per-VCPU statistic to KVM debugfs to show if a given
VCPU is running a nested guest:

	nested_guest_running

Also add this as a per-VM statistic to KVM debugfs to show the total number
of VCPUs running a nested guest in a given VM.

Signed-off-by: Krish Sadhukhan <Krish.Sadhukhan@xxxxxxxxxx>
---
 arch/x86/include/asm/kvm_host.h |  1 +
 arch/x86/kvm/debugfs.c          | 11 +++++++++++
 arch/x86/kvm/kvm_cache_regs.h   |  3 +++
 arch/x86/kvm/x86.c              |  1 +
 4 files changed, 16 insertions(+)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index cf8557b2b90f..884f6e5ba669 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1173,6 +1173,7 @@ struct kvm_vcpu_stat {
 	u64 nested_runs;
 	u64 directed_yield_attempted;
 	u64 directed_yield_successful;
+	u64 nested_guest_running;
 };
 
 struct x86_instruction_info;
diff --git a/arch/x86/kvm/debugfs.c b/arch/x86/kvm/debugfs.c
index 7e818d64bb4d..465d243afaac 100644
--- a/arch/x86/kvm/debugfs.c
+++ b/arch/x86/kvm/debugfs.c
@@ -17,6 +17,15 @@ static int vcpu_get_timer_advance_ns(void *data, u64 *val)
 
 DEFINE_SIMPLE_ATTRIBUTE(vcpu_timer_advance_ns_fops, vcpu_get_timer_advance_ns, NULL, "%llu\n");
 
+static int vcpu_get_guest_mode(void *data, u64 *val)
+{
+	struct kvm_vcpu *vcpu = (struct kvm_vcpu *) data;
+	*val = vcpu->stat.nested_guest_running;
+	return 0;
+}
+
+DEFINE_SIMPLE_ATTRIBUTE(vcpu_guest_mode_fops, vcpu_get_guest_mode, NULL, "%lld\n");
+
 static int vcpu_get_tsc_offset(void *data, u64 *val)
 {
 	struct kvm_vcpu *vcpu = (struct kvm_vcpu *) data;
@@ -45,6 +54,8 @@ DEFINE_SIMPLE_ATTRIBUTE(vcpu_tsc_scaling_frac_fops, vcpu_get_tsc_scaling_frac_bi
 
 void kvm_arch_create_vcpu_debugfs(struct kvm_vcpu *vcpu, struct dentry *debugfs_dentry)
 {
+	debugfs_create_file("nested_guest_running", 0444, debugfs_dentry, vcpu,
+			    &vcpu_guest_mode_fops);
 	debugfs_create_file("tsc-offset", 0444, debugfs_dentry, vcpu,
 			    &vcpu_tsc_offset_fops);
 
diff --git a/arch/x86/kvm/kvm_cache_regs.h b/arch/x86/kvm/kvm_cache_regs.h
index cf52cbff18d3..348ef98c6199 100644
--- a/arch/x86/kvm/kvm_cache_regs.h
+++ b/arch/x86/kvm/kvm_cache_regs.h
@@ -163,6 +163,7 @@ static inline void enter_guest_mode(struct kvm_vcpu *vcpu)
 {
 	vcpu->arch.hflags |= HF_GUEST_MASK;
 	++vcpu->stat.nested_runs;
+	vcpu->stat.nested_guest_running = 1;
 }
 
 static inline void leave_guest_mode(struct kvm_vcpu *vcpu)
@@ -173,6 +174,8 @@ static inline void leave_guest_mode(struct kvm_vcpu *vcpu)
 		vcpu->arch.load_eoi_exitmap_pending = false;
 		kvm_make_request(KVM_REQ_LOAD_EOI_EXITMAP, vcpu);
 	}
+
+	vcpu->stat.nested_guest_running = 0;
 }
 
 static inline bool is_guest_mode(struct kvm_vcpu *vcpu)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 6d1f51f6c344..01805b68dc9b 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -246,6 +246,7 @@ struct kvm_stats_debugfs_item debugfs_entries[] = {
 	VCPU_STAT("nested_runs", nested_runs),
 	VCPU_STAT("directed_yield_attempted", directed_yield_attempted),
 	VCPU_STAT("directed_yield_successful", directed_yield_successful),
+	VCPU_STAT("nested_guest_running", nested_guest_running),
 	VM_STAT("mmu_shadow_zapped", mmu_shadow_zapped),
 	VM_STAT("mmu_pte_write", mmu_pte_write),
 	VM_STAT("mmu_pde_zapped", mmu_pde_zapped),
-- 
2.27.0