On Wed, Jan 07, 2026 at 03:40:22PM +0000, Marc Zyngier wrote: > On Tue, 02 Dec 2025 09:36:22 +0000, > Vincent Donnefort <[email protected]> wrote: > > > > Add a selftest event that can be triggered from a `write_event` tracefs > > file. This intends to be used by trace remote selftests. > > > > Signed-off-by: Vincent Donnefort <[email protected]> > > > > diff --git a/arch/arm64/include/asm/kvm_asm.h > > b/arch/arm64/include/asm/kvm_asm.h > > index 37c015b54ff6..e2de7ad64938 100644 > > --- a/arch/arm64/include/asm/kvm_asm.h > > +++ b/arch/arm64/include/asm/kvm_asm.h > > @@ -96,6 +96,7 @@ enum __kvm_host_smccc_func { > > __KVM_HOST_SMCCC_FUNC___tracing_update_clock, > > __KVM_HOST_SMCCC_FUNC___tracing_reset, > > __KVM_HOST_SMCCC_FUNC___tracing_enable_event, > > + __KVM_HOST_SMCCC_FUNC___tracing_write_event, > > }; > > > > #define DECLARE_KVM_VHE_SYM(sym) extern char sym[] > > diff --git a/arch/arm64/include/asm/kvm_hypevents.h > > b/arch/arm64/include/asm/kvm_hypevents.h > > index 268b3cd7a1b2..c276fd28e0bf 100644 > > --- a/arch/arm64/include/asm/kvm_hypevents.h > > +++ b/arch/arm64/include/asm/kvm_hypevents.h > > @@ -42,4 +42,15 @@ HYP_EVENT(hyp_exit, > > ), > > HE_PRINTK("reason=%s", __hyp_enter_exit_reason_str(__entry->reason)) > > ); > > + > > +HYP_EVENT(selftest, > > + HE_PROTO(u64 id), > > + HE_STRUCT( > > + he_field(u64, id) > > + ), > > + HE_ASSIGN( > > + __entry->id = id; > > + ), > > + RE_PRINTK("id=%llu", __entry->id) > > Not strictly related to this patch, but I find that the trace itself > lacks context. For example: > > [001] 323.847422: hyp_enter reason=hvc > [001] 323.847423: hyp_exit reason=eret_host > [001] 323.847688: hyp_enter reason=hvc > [001] 323.847688: hyp_exit reason=eret_host > [001] 323.847706: hyp_enter reason=hvc > [001] 323.847707: hyp_exit reason=eret_host > [001] 323.847722: hyp_enter reason=hvc > [001] 323.847723: hyp_exit reason=eret_host > > That's all fine as long as I'm dealing with a single guest, or even > with a single vcpu. Trying to trace multiple guests, or even multiple > vcpus makes the whole thing completely unusable, because I have no > idea what I'm looking at. > > To make this useful, having some context provided by the host really > is required.
I could add to the event header the VM pid related to the currently loaded vCPU (if any). I can access it easily with host_kvm->userspace_pid. WDYS? > > Thanks, > > M. > > -- > Without deviation from the norm, progress is not possible.
