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SubjectRe: [PATCH 5/6] KVM: x86: Rename "found" variable in kvm_cpuid() to "exact_entry_exists"
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On 02.03.20 21:35, Sean Christopherson wrote:
> On Mon, Mar 02, 2020 at 09:20:52PM +0100, Jan Kiszka wrote:
>> On 02.03.20 20:57, Sean Christopherson wrote:
>>> Rename "found" in kvm_cpuid() to "exact_entry_exists" to better convey
>>> that the intent of the tracepoint's "found/not found" output is to trace
>>> whether the output values are for the actual requested leaf or for some
>>> other (likely unrelated) leaf that was found while processing entries to
>>> emulate funky CPU behavior, e.g. the max basic leaf on Intel CPUs when
>>> the requested CPUID leaf is out of range.
>>>
>>> Suggested-by: Jan Kiszka <jan.kiszka@siemens.com>
>>> Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
>>> ---
>>> arch/x86/kvm/cpuid.c | 6 +++---
>>> 1 file changed, 3 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
>>> index 869526930cf7..b0a4f3c17932 100644
>>> --- a/arch/x86/kvm/cpuid.c
>>> +++ b/arch/x86/kvm/cpuid.c
>>> @@ -1002,10 +1002,10 @@ void kvm_cpuid(struct kvm_vcpu *vcpu, u32 *eax, u32 *ebx,
>>> {
>>> const u32 function = *eax, index = *ecx;
>>> struct kvm_cpuid_entry2 *entry;
>>> - bool found;
>>> + bool exact_entry_exists;
>>> entry = kvm_find_cpuid_entry(vcpu, function, index);
>>> - found = entry;
>>> + exact_entry_exists = !!entry;
>>> /*
>>> * Intel CPUID semantics treats any query for an out-of-range
>>> * leaf as if the highest basic leaf (i.e. CPUID.0H:EAX) were
>>> @@ -1047,7 +1047,7 @@ void kvm_cpuid(struct kvm_vcpu *vcpu, u32 *eax, u32 *ebx,
>>> }
>>> }
>>> }
>>> - trace_kvm_cpuid(function, *eax, *ebx, *ecx, *edx, found);
>>> + trace_kvm_cpuid(function, *eax, *ebx, *ecx, *edx, exact_entry_exists);
>>
>> Actually, I think we also what to change output in the tracepoint.
>
> Oh, I definitely want to change it, but AIUI it's ABI and shouldn't be
> changed. Paolo?
>

This can be discovered via the format string in sysfs and handled by the
consumer. But I'm not an expert in the tracing ABI.

Jan

--
Siemens AG, Corporate Technology, CT RDA IOT SES-DE
Corporate Competence Center Embedded Linux

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