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Subject[PATCH 1/2] KVM: x86: Add requested index to the CPUID tracepoint
Date
Output the requested index when tracing CPUID emulation; it's basically
mandatory for leafs where the index is meaningful, and is helpful for
verifying KVM correctness even when the index isn't meaningful, e.g. the
trace for a Linux guest's hypervisor_cpuid_base() probing appears to
be broken (returns all zeroes) at first glance, but is correct because
the index is non-zero, i.e. the output values correspond to a random
index in the maximum basic leaf.

Suggested-by: Xiaoyao Li <xiaoyao.li@intel.com>
Cc: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
---
arch/x86/kvm/cpuid.c | 2 +-
arch/x86/kvm/trace.h | 13 ++++++++-----
2 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index 08280d8a2ac9..bccaae0df668 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -1026,7 +1026,7 @@ bool kvm_cpuid(struct kvm_vcpu *vcpu, u32 *eax, u32 *ebx,
}
}
}
- trace_kvm_cpuid(orig_function, *eax, *ebx, *ecx, *edx, exact);
+ trace_kvm_cpuid(orig_function, index, *eax, *ebx, *ecx, *edx, exact);
return exact;
}
EXPORT_SYMBOL_GPL(kvm_cpuid);
diff --git a/arch/x86/kvm/trace.h b/arch/x86/kvm/trace.h
index 6c4d9b4caf07..27270ba0f05f 100644
--- a/arch/x86/kvm/trace.h
+++ b/arch/x86/kvm/trace.h
@@ -151,12 +151,14 @@ TRACE_EVENT(kvm_fast_mmio,
* Tracepoint for cpuid.
*/
TRACE_EVENT(kvm_cpuid,
- TP_PROTO(unsigned int function, unsigned long rax, unsigned long rbx,
- unsigned long rcx, unsigned long rdx, bool found),
- TP_ARGS(function, rax, rbx, rcx, rdx, found),
+ TP_PROTO(unsigned int function, unsigned int index, unsigned long rax,
+ unsigned long rbx, unsigned long rcx, unsigned long rdx,
+ bool found),
+ TP_ARGS(function, index, rax, rbx, rcx, rdx, found),

TP_STRUCT__entry(
__field( unsigned int, function )
+ __field( unsigned int, index )
__field( unsigned long, rax )
__field( unsigned long, rbx )
__field( unsigned long, rcx )
@@ -166,6 +168,7 @@ TRACE_EVENT(kvm_cpuid,

TP_fast_assign(
__entry->function = function;
+ __entry->index = index;
__entry->rax = rax;
__entry->rbx = rbx;
__entry->rcx = rcx;
@@ -173,8 +176,8 @@ TRACE_EVENT(kvm_cpuid,
__entry->found = found;
),

- TP_printk("func %x rax %lx rbx %lx rcx %lx rdx %lx, cpuid entry %s",
- __entry->function, __entry->rax,
+ TP_printk("func %x idx %x rax %lx rbx %lx rcx %lx rdx %lx, cpuid entry %s",
+ __entry->function, __entry->index, __entry->rax,
__entry->rbx, __entry->rcx, __entry->rdx,
__entry->found ? "found" : "not found")
);
--
2.24.1
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