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[34.34.145.44]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-b885b6ff08csm99028966b.43.2026.01.23.04.14.37 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 23 Jan 2026 04:14:37 -0800 (PST) Date: Fri, 23 Jan 2026 12:14:34 +0000 From: Vincent Donnefort To: Marc Zyngier Cc: rostedt@goodmis.org, mhiramat@kernel.org, mathieu.desnoyers@efficios.com, linux-trace-kernel@vger.kernel.org, oliver.upton@linux.dev, joey.gouly@arm.com, suzuki.poulose@arm.com, yuzenghui@huawei.com, kvmarm@lists.linux.dev, linux-arm-kernel@lists.infradead.org, jstultz@google.com, qperret@google.com, will@kernel.org, aneesh.kumar@kernel.org, kernel-team@android.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH v9 29/30] KVM: arm64: Add selftest event support to nVHE/pKVM hyp Message-ID: References: <20251202093623.2337860-1-vdonnefort@google.com> <20251202093623.2337860-30-vdonnefort@google.com> <868qe9mnx5.wl-maz@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <868qe9mnx5.wl-maz@kernel.org> On Wed, Jan 07, 2026 at 03:40:22PM +0000, Marc Zyngier wrote: > On Tue, 02 Dec 2025 09:36:22 +0000, > Vincent Donnefort 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 > > > > 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.