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SubjectRe: [PATCH v2 2/3] KVM: nVMX: add kvm_nested_vmlaunch_resume tracepoint
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On 15/01/21 01:14, Sean Christopherson wrote:
>> + trace_kvm_nested_vmlaunch_resume(kvm_rip_read(vcpu),
> Hmm, won't this RIP be wrong for the migration case? I.e. it'll be L2, not L1
> as is the case for the "true" nested VM-Enter path.

It will be the previous RIP---might as well be 0xfffffff0 depending on
what userspace does. I don't think you can do much better than that,
using vmcs12->host_rip would be confusing in the SMM case.

>> + vmx->nested.current_vmptr,
>> + vmcs12->guest_rip,
>> + vmcs12->vm_entry_intr_info_field);
> The placement is a bit funky. I assume you put it here so that calls from
> vmx_set_nested_state() also get traced. But, that also means
> vmx_pre_leave_smm() will get traced, and it also creates some weirdness where
> some nested VM-Enters that VM-Fail will get traced, but others will not.
>
> Tracing vmx_pre_leave_smm() isn't necessarily bad, but it could be confusing,
> especially if the debugger looks up the RIP and sees RSM. Ditto for the
> migration case.

Actually tracing vmx_pre_leave_smm() is good, and pointing to RSM makes
sense so I'm not worried about that.

Paolo

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