[PATCH 4/4] KVM: x86: add new nested vmexit tracepoints
From: Maxim Levitsky
Date: Wed Aug 30 2023 - 15:08:47 EST
Add 3 new tracepoints for nested VM exits which are intended
to capture extra information to gain insights about the nested guest
behavior.
The new tracepoints are:
- kvm_nested_msr
- kvm_nested_hypercall
These tracepoints capture extra register state to be able to know
which MSR or which hypercall was done.
- kvm_nested_page_fault
This tracepoint allows to capture extra info about which host pagefault
error code caused the nested page fault.
Signed-off-by: Maxim Levitsky <mlevitsk@xxxxxxxxxx>
---
arch/x86/include/asm/kvm_host.h | 1 +
arch/x86/kvm/svm/nested.c | 22 +++++++++
arch/x86/kvm/trace.h | 82 +++++++++++++++++++++++++++++++--
arch/x86/kvm/vmx/nested.c | 21 +++++++++
arch/x86/kvm/vmx/vmx.c | 1 +
arch/x86/kvm/x86.c | 3 ++
6 files changed, 127 insertions(+), 3 deletions(-)
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 9cc5ac420f4052..9a72a078d126c9 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -948,6 +948,7 @@ struct kvm_vcpu_arch {
/* set at EPT violation at this point */
unsigned long exit_qualification;
+ u32 ept_fault_error_code;
/* pv related host specific info */
struct {
diff --git a/arch/x86/kvm/svm/nested.c b/arch/x86/kvm/svm/nested.c
index 96936ddf1b3c56..d24bd21fbdc728 100644
--- a/arch/x86/kvm/svm/nested.c
+++ b/arch/x86/kvm/svm/nested.c
@@ -38,6 +38,8 @@ static void nested_svm_inject_npf_exit(struct kvm_vcpu *vcpu,
{
struct vcpu_svm *svm = to_svm(vcpu);
struct vmcb *vmcb = svm->vmcb;
+ u64 host_error_code = vmcb->control.exit_info_1;
+
if (vmcb->control.exit_code != SVM_EXIT_NPF) {
/*
@@ -48,11 +50,15 @@ static void nested_svm_inject_npf_exit(struct kvm_vcpu *vcpu,
vmcb->control.exit_code_hi = 0;
vmcb->control.exit_info_1 = (1ULL << 32);
vmcb->control.exit_info_2 = fault->address;
+ host_error_code = 0;
}
vmcb->control.exit_info_1 &= ~0xffffffffULL;
vmcb->control.exit_info_1 |= fault->error_code;
+ trace_kvm_nested_page_fault(fault->address, host_error_code,
+ fault->error_code);
+
nested_svm_vmexit(svm);
}
@@ -1130,6 +1136,22 @@ int nested_svm_vmexit(struct vcpu_svm *svm)
vmcb12->control.exit_int_info_err,
KVM_ISA_SVM);
+ /* Collect some info about nested VM exits */
+ switch (vmcb12->control.exit_code) {
+ case SVM_EXIT_MSR:
+ trace_kvm_nested_msr(vmcb12->control.exit_info_1 == 1,
+ kvm_rcx_read(vcpu),
+ (vmcb12->save.rax & -1u) |
+ (((u64)(kvm_rdx_read(vcpu) & -1u) << 32)));
+ break;
+ case SVM_EXIT_VMMCALL:
+ trace_kvm_nested_hypercall(vmcb12->save.rax,
+ kvm_rbx_read(vcpu),
+ kvm_rcx_read(vcpu),
+ kvm_rdx_read(vcpu));
+ break;
+ }
+
kvm_vcpu_unmap(vcpu, &map, true);
nested_svm_transition_tlb_flush(vcpu);
diff --git a/arch/x86/kvm/trace.h b/arch/x86/kvm/trace.h
index 0657a3a348b4ae..d08ae87c536324 100644
--- a/arch/x86/kvm/trace.h
+++ b/arch/x86/kvm/trace.h
@@ -620,7 +620,7 @@ TRACE_EVENT(kvm_pv_eoi,
);
/*
- * Tracepoint for nested VMRUN
+ * Tracepoint for nested VMRUN/VMENTER
*/
TRACE_EVENT(kvm_nested_vmenter,
TP_PROTO(__u64 rip, __u64 vmcb, __u64 nested_rip, __u32 int_ctl,
@@ -753,8 +753,84 @@ TRACE_EVENT(kvm_nested_intr_vmexit,
TP_printk("rip: 0x%016llx", __entry->rip)
);
+
/*
- * Tracepoint for nested #vmexit because of interrupt pending
+ * Tracepoint for nested guest MSR access.
+ */
+TRACE_EVENT(kvm_nested_msr,
+ TP_PROTO(bool write, u32 ecx, u64 data),
+ TP_ARGS(write, ecx, data),
+
+ TP_STRUCT__entry(
+ __field( bool, write )
+ __field( u32, ecx )
+ __field( u64, data )
+ ),
+
+ TP_fast_assign(
+ __entry->write = write;
+ __entry->ecx = ecx;
+ __entry->data = data;
+ ),
+
+ TP_printk("msr_%s %x = 0x%llx",
+ __entry->write ? "write" : "read",
+ __entry->ecx, __entry->data)
+);
+
+/*
+ * Tracepoint for nested hypercalls, capturing generic info about the
+ * hypercall
+ */
+
+TRACE_EVENT(kvm_nested_hypercall,
+ TP_PROTO(u64 rax, u64 rbx, u64 rcx, u64 rdx),
+ TP_ARGS(rax, rbx, rcx, rdx),
+
+ TP_STRUCT__entry(
+ __field( u64, rax )
+ __field( u64, rbx )
+ __field( u64, rcx )
+ __field( u64, rdx )
+ ),
+
+ TP_fast_assign(
+ __entry->rax = rax;
+ __entry->rbx = rbx;
+ __entry->rcx = rcx;
+ __entry->rdx = rdx;
+ ),
+
+ TP_printk("rax 0x%llx rbx 0x%llx rcx 0x%llx rdx 0x%llx",
+ __entry->rax, __entry->rbx, __entry->rcx, __entry->rdx)
+);
+
+
+TRACE_EVENT(kvm_nested_page_fault,
+ TP_PROTO(u64 gpa, u64 host_error_code, u64 guest_error_code),
+ TP_ARGS(gpa, host_error_code, guest_error_code),
+
+ TP_STRUCT__entry(
+ __field( u64, gpa )
+ __field( u64, host_error_code )
+ __field( u64, guest_errror_code )
+ ),
+
+ TP_fast_assign(
+ __entry->gpa = gpa;
+ __entry->host_error_code = host_error_code;
+ __entry->guest_errror_code = guest_error_code;
+ ),
+
+ TP_printk("gpa 0x%llx host err 0x%llx guest err 0x%llx",
+ __entry->gpa,
+ __entry->host_error_code,
+ __entry->guest_errror_code)
+);
+
+
+/*
+ * Tracepoint for invlpga
*/
TRACE_EVENT(kvm_invlpga,
TP_PROTO(__u64 rip, int asid, u64 address),
@@ -777,7 +853,7 @@ TRACE_EVENT(kvm_invlpga,
);
/*
- * Tracepoint for nested #vmexit because of interrupt pending
+ * Tracepoint for skinit
*/
TRACE_EVENT(kvm_skinit,
TP_PROTO(__u64 rip, __u32 slb),
diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
index 516391cc0d64fb..303472aa4d7e85 100644
--- a/arch/x86/kvm/vmx/nested.c
+++ b/arch/x86/kvm/vmx/nested.c
@@ -402,6 +402,10 @@ static void nested_ept_inject_page_fault(struct kvm_vcpu *vcpu,
*/
nested_ept_invalidate_addr(vcpu, vmcs12->ept_pointer,
fault->address);
+
+ trace_kvm_nested_page_fault(fault->address,
+ vcpu->arch.ept_fault_error_code,
+ fault->error_code);
}
nested_vmx_vmexit(vcpu, vm_exit_reason, 0, exit_qualification);
@@ -4877,6 +4881,23 @@ void nested_vmx_vmexit(struct kvm_vcpu *vcpu, u32 vm_exit_reason,
vmcs12->vm_exit_intr_error_code,
KVM_ISA_VMX);
+ switch ((u16)vmcs12->vm_exit_reason) {
+ case EXIT_REASON_MSR_READ:
+ case EXIT_REASON_MSR_WRITE:
+ trace_kvm_nested_msr(vmcs12->vm_exit_reason == EXIT_REASON_MSR_WRITE,
+ kvm_rcx_read(vcpu),
+ (kvm_rax_read(vcpu) & -1u) |
+ (((u64)(kvm_rdx_read(vcpu) & -1u) << 32)));
+ break;
+ case EXIT_REASON_VMCALL:
+ trace_kvm_nested_hypercall(kvm_rax_read(vcpu),
+ kvm_rbx_read(vcpu),
+ kvm_rcx_read(vcpu),
+ kvm_rdx_read(vcpu));
+ break;
+
+ }
+
load_vmcs12_host_state(vcpu, vmcs12);
return;
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index d662d546232171..649f09a350e9a1 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -5774,6 +5774,7 @@ static int handle_ept_violation(struct kvm_vcpu *vcpu)
PFERR_GUEST_FINAL_MASK : PFERR_GUEST_PAGE_MASK;
vcpu->arch.exit_qualification = exit_qualification;
+ vcpu->arch.ept_fault_error_code = error_code;
/*
* Check that the GPA doesn't exceed physical memory limits, as that is
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 53f0a5f493be37..d46b9f3f44428b 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -13628,6 +13628,9 @@ EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_nested_vmenter);
EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_nested_vmexit);
EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_nested_vmexit_inject);
EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_nested_intr_vmexit);
+EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_nested_hypercall);
+EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_nested_page_fault);
+EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_nested_msr);
EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_nested_vmenter_failed);
EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_invlpga);
EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_skinit);
--
2.26.3