[PATCH v6 03/16] KVM: nSVM: Move VMRUN instruction retirement after entering guest mode

[Yosry Ahmed]

A successful VMRUN retires in guest mode and should be counted by the
PMU as a guest instruction. However, __kvm_skip_emulated_instruction()
is called before entering guest mode to advance L1's RIP to the
instruction following VMRUN. This is needed as the RIP is saved in
vmcb01 to be restored on VM-Exit.

Since VMRUN emulation is the only caller of
__kvm_skip_emulated_instruction(), move retiring instructions for PMU
purposes to its wrapper, leaving __kvm_skip_emulated_instruction() as a
transparent wrapper around the vendor-specific calls.

Note that this is currently a noop because KVM does not virtualize
Host-Only/Guest-Only PMC controls yet, so all instructions are counted
regardless of the vCPU's host/guest state. But this change is needed for
the incoming support for Host-Only/Guest-Only controls to count VMRUN
correctly.

Signed-off-by: Yosry Ahmed <yosry@xxxxxxxxxx>
---
 arch/x86/kvm/svm/nested.c |  9 ++++++++-
 arch/x86/kvm/x86.c        | 11 +++--------
 2 files changed, 11 insertions(+), 9 deletions(-)

diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
index 0f6ea490d707b..58c78c889a812 100644
--- a/arch/x86/kvm/svm/nested.c
+++ b/arch/x86/kvm/svm/nested.c
@@ -30,6 +30,7 @@
 #include "lapic.h"
 #include "svm.h"
 #include "hyperv.h"
+#include "pmu.h"
 
 #define CC KVM_NESTED_VMENTER_CONSISTENCY_CHECK
 
@@ -1135,7 +1136,7 @@ int nested_svm_vmrun(struct kvm_vcpu *vcpu)
 		return 0;
 
 	if (ret)
-		return 1;
+		goto insn_retired;
 
 	/*
 	 * Since vmcb01 is not in use, we can use it to store some of the L1
@@ -1165,6 +1166,12 @@ int nested_svm_vmrun(struct kvm_vcpu *vcpu)
 		nested_svm_vmexit(svm);
 	}
 
+insn_retired:
+	/*
+	 * A successful VMRUN is counted by the PMU in guest mode, so only
+	 * retire the instruction after potentially entering guest mode.
+	 */
+	kvm_pmu_instruction_retired(vcpu);
 	return 1;
 }
 
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 31dc48a8111e5..08be0a63b93bd 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -9274,14 +9274,7 @@ static int kvm_vcpu_do_singlestep(struct kvm_vcpu *vcpu)
 
 int __kvm_skip_emulated_instruction(struct kvm_vcpu *vcpu)
 {
-	int r;
-
-	r = kvm_x86_call(skip_emulated_instruction)(vcpu);
-	if (unlikely(!r))
-		return 0;
-
-	kvm_pmu_instruction_retired(vcpu);
-	return r;
+	return kvm_x86_call(skip_emulated_instruction)(vcpu);
 }
 EXPORT_SYMBOL_FOR_KVM_INTERNAL(__kvm_skip_emulated_instruction);
 
@@ -9294,6 +9287,8 @@ int kvm_skip_emulated_instruction(struct kvm_vcpu *vcpu)
 	if (unlikely(!r))
 		return 0;
 
+	kvm_pmu_instruction_retired(vcpu);
+
 	/*
 	 * rflags is the old, "raw" value of the flags.  The new value has
 	 * not been saved yet.
-- 
2.54.0.545.g6539524ca2-goog