linux-kernel - [PATCH 2/7] KVM: x86: Read guest RIP from within the kvm_nested

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Date:   Fri, 17 Jul 2020 23:38:49 -0700
From:   Sean Christopherson <sean.j.christopherson@...el.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Sean Christopherson <sean.j.christopherson@...el.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 2/7] KVM: x86: Read guest RIP from within the kvm_nested_vmexit tracepoint

Use kvm_rip_read() to read the guest's RIP for the nested VM-Exit
tracepoint instead of having the caller pass in the tracepoint.  Params
that are passed into a tracepoint are evaluated even if the tracepoint
is disabled, i.e. passing in RIP for VMX incurs a VMREAD and retpoline
to retrieve a value that may never be used, e.g. if the exit is due to a
hardware interrupt.

Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
---
 arch/x86/kvm/svm/svm.c    | 2 +-
 arch/x86/kvm/trace.h      | 6 +++---
 arch/x86/kvm/vmx/nested.c | 2 +-
 3 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 783330d0e7b88..1fea39ff33077 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -2943,7 +2943,7 @@ static int handle_exit(struct kvm_vcpu *vcpu, fastpath_t exit_fastpath)
 	if (is_guest_mode(vcpu)) {
 		int vmexit;
 
-		trace_kvm_nested_vmexit(svm->vmcb->save.rip, exit_code,
+		trace_kvm_nested_vmexit(vcpu, exit_code,
 					svm->vmcb->control.exit_info_1,
 					svm->vmcb->control.exit_info_2,
 					svm->vmcb->control.exit_int_info,
diff --git a/arch/x86/kvm/trace.h b/arch/x86/kvm/trace.h
index 9899ff0fa2534..00e567378ae1f 100644
--- a/arch/x86/kvm/trace.h
+++ b/arch/x86/kvm/trace.h
@@ -571,10 +571,10 @@ TRACE_EVENT(kvm_nested_intercepts,
  * Tracepoint for #VMEXIT while nested
  */
 TRACE_EVENT(kvm_nested_vmexit,
-	    TP_PROTO(__u64 rip, __u32 exit_code,
+	    TP_PROTO(struct kvm_vcpu *vcpu, __u32 exit_code,
 		     __u64 exit_info1, __u64 exit_info2,
 		     __u32 exit_int_info, __u32 exit_int_info_err, __u32 isa),
-	    TP_ARGS(rip, exit_code, exit_info1, exit_info2,
+	    TP_ARGS(vcpu, exit_code, exit_info1, exit_info2,
 		    exit_int_info, exit_int_info_err, isa),
 
 	TP_STRUCT__entry(
@@ -588,7 +588,7 @@ TRACE_EVENT(kvm_nested_vmexit,
 	),
 
 	TP_fast_assign(
-		__entry->rip			= rip;
+		__entry->rip			= kvm_rip_read(vcpu);
 		__entry->exit_code		= exit_code;
 		__entry->exit_info1		= exit_info1;
 		__entry->exit_info2		= exit_info2;
diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 4d561edf6f9ca..6f81097cbc794 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -5912,7 +5912,7 @@ bool nested_vmx_reflect_vmexit(struct kvm_vcpu *vcpu)
 	exit_intr_info = vmx_get_intr_info(vcpu);
 	exit_qual = vmx_get_exit_qual(vcpu);
 
-	trace_kvm_nested_vmexit(kvm_rip_read(vcpu), exit_reason, exit_qual,
+	trace_kvm_nested_vmexit(vcpu, exit_reason, exit_qual,
 				vmx->idt_vectoring_info, exit_intr_info,
 				vmcs_read32(VM_EXIT_INTR_ERROR_CODE),
 				KVM_ISA_VMX);
-- 
2.26.0