Hi Sean, Hi Paolo,
I have a question regarding a unexport of kvm_x86_ops that made its
way into 5.18-rc (commit dfc4e6ca04 ("KVM: x86: Unexport kvm_x86_ops").
This is in the context of tracing. Especially, LTTng implements probes
for x86 kvm events, e.g. x86 kvm_exit. It receives a struct kvm_vcpu *
as parameter, and uses kvm_x86_ops.get_exit_info() to translate this
into meaningful fields.
LTTng is an out of tree kernel module, which currently relies on the export.
Indeed, arch/x86/kvm/x86.c exports a set of tracepoints to kernel modules, e.g.:
EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_entry)
But any probe implementation hooking on that tracepoint would need kvm_x86_ops
to translate the struct kvm_vcpu * into meaningful tracing data.
I could work-around this on my side in ugly ways, but I would like to discuss
how kernel module tracers are expected to implement kvm events probes without
the kvm_x86_ops symbol ? Perhaps there is an alternative way to convert the
fields in this structure to meaningful information without using the
kvm_x86_ops callbacks that I am not aware of ?
The LTTng kernel tracer uses get_exit_info() and get_segment_base() callbacks
from kvm_x86_ops.
Thanks,
Mathieu
--
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com
