Re: [PATCH v9 28/30] KVM: arm64: Add hyp_enter/hyp_exit events to nVHE/pKVM hyp

Marc Zyngier
2026-01-07T14:37:38Z

On Tue, 02 Dec 2025 09:36:21 +0000,
Vincent Donnefort <vdonnefort@google.com> wrote:
>
> The hyp_enter and hyp_exit events are logged by the hypervisor any time
> it is entered and exited.
>
> Signed-off-by: Vincent Donnefort <vdonnefort@google.com>
>
> diff --git a/arch/arm64/include/asm/kvm_hypevents.h b/arch/arm64/include/asm/kvm_hypevents.h
> index d6e033c96c52..268b3cd7a1b2 100644
> --- a/arch/arm64/include/asm/kvm_hypevents.h
> +++ b/arch/arm64/include/asm/kvm_hypevents.h
> @@ -7,4 +7,39 @@
> #include <nvhe/trace.h>
> #endif
>
> +#ifndef __HYP_ENTER_EXIT_REASON
> +#define __HYP_ENTER_EXIT_REASON
> +enum hyp_enter_exit_reason {
> + HYP_REASON_SMC,
> + HYP_REASON_HVC,
> + HYP_REASON_PSCI,
> + HYP_REASON_HOST_ABORT,
> + HYP_REASON_GUEST_EXIT,
> + HYP_REASON_ERET_HOST,
> + HYP_REASON_ERET_GUEST,
> + HYP_REASON_UNKNOWN /* Must be last */
> +};
> +#endif
> +
> +HYP_EVENT(hyp_enter,
> + HE_PROTO(u8 reason),
> + HE_STRUCT(
> + he_field(u8, reason)
> + ),
> + HE_ASSIGN(
> + __entry->reason = reason;
> + ),
> + HE_PRINTK("reason=%s", __hyp_enter_exit_reason_str(__entry->reason))
> +);
> +
> +HYP_EVENT(hyp_exit,
> + HE_PROTO(u8 reason),
> + HE_STRUCT(
> + he_field(u8, reason)
> + ),
> + HE_ASSIGN(
> + __entry->reason = reason;
> + ),
> + HE_PRINTK("reason=%s", __hyp_enter_exit_reason_str(__entry->reason))
> +);
> #endif
> diff --git a/arch/arm64/kvm/hyp/include/nvhe/arm-smccc.h b/arch/arm64/kvm/hyp/include/nvhe/arm-smccc.h
> new file mode 100644
> index 000000000000..7cd0f701f3c9
> --- /dev/null
> +++ b/arch/arm64/kvm/hyp/include/nvhe/arm-smccc.h
> @@ -0,0 +1,23 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +#ifndef __ARM64_KVM_HYP_NVHE_ARM_SMCCC_H__
> +#define __ARM64_KVM_HYP_NVHE_ARM_SMCCC_H__
> +
> +#include <asm/kvm_hypevents.h>
> +
> +#include <linux/arm-smccc.h>
> +
> +#define hyp_smccc_1_1_smc(...) \
> + do { \
> + trace_hyp_exit(HYP_REASON_SMC); \
> + arm_smccc_1_1_smc(__VA_ARGS__); \
> + trace_hyp_enter(HYP_REASON_SMC); \
> + } while (0)
> +
> +#define hyp_smccc_1_2_smc(...) \
> + do { \
> + trace_hyp_exit(HYP_REASON_SMC); \
> + arm_smccc_1_2_smc(__VA_ARGS__); \
> + trace_hyp_enter(HYP_REASON_SMC); \
> + } while (0)
> +
> +#endif /* __ARM64_KVM_HYP_NVHE_ARM_SMCCC_H__ */
> diff --git a/arch/arm64/kvm/hyp/nvhe/ffa.c b/arch/arm64/kvm/hyp/nvhe/ffa.c
> index 58b7d0c477d7..73d79f9de850 100644
> --- a/arch/arm64/kvm/hyp/nvhe/ffa.c
> +++ b/arch/arm64/kvm/hyp/nvhe/ffa.c
> @@ -26,10 +26,10 @@
> * the duration and are therefore serialised.
> */
>
> -#include <linux/arm-smccc.h>
> #include <linux/arm_ffa.h>
> #include <asm/kvm_pkvm.h>
>
> +#include <nvhe/arm-smccc.h>
> #include <nvhe/ffa.h>
> #include <nvhe/mem_protect.h>
> #include <nvhe/memory.h>
> @@ -147,7 +147,7 @@ static int ffa_map_hyp_buffers(u64 ffa_page_count)
> {
> struct arm_smccc_1_2_regs res;
>
> - arm_smccc_1_2_smc(&(struct arm_smccc_1_2_regs) {
> + hyp_smccc_1_2_smc(&(struct arm_smccc_1_2_regs) {
> .a0 = FFA_FN64_RXTX_MAP,
> .a1 = hyp_virt_to_phys(hyp_buffers.tx),
> .a2 = hyp_virt_to_phys(hyp_buffers.rx),
> @@ -161,7 +161,7 @@ static int ffa_unmap_hyp_buffers(void)
> {
> struct arm_smccc_1_2_regs res;
>
> - arm_smccc_1_2_smc(&(struct arm_smccc_1_2_regs) {
> + hyp_smccc_1_2_smc(&(struct arm_smccc_1_2_regs) {
> .a0 = FFA_RXTX_UNMAP,
> .a1 = HOST_FFA_ID,
> }, &res);
> @@ -172,7 +172,7 @@ static int ffa_unmap_hyp_buffers(void)
> static void ffa_mem_frag_tx(struct arm_smccc_1_2_regs *res, u32 handle_lo,
> u32 handle_hi, u32 fraglen, u32 endpoint_id)
> {
> - arm_smccc_1_2_smc(&(struct arm_smccc_1_2_regs) {
> + hyp_smccc_1_2_smc(&(struct arm_smccc_1_2_regs) {
> .a0 = FFA_MEM_FRAG_TX,
> .a1 = handle_lo,
> .a2 = handle_hi,
> @@ -184,7 +184,7 @@ static void ffa_mem_frag_tx(struct arm_smccc_1_2_regs *res, u32 handle_lo,
> static void ffa_mem_frag_rx(struct arm_smccc_1_2_regs *res, u32 handle_lo,
> u32 handle_hi, u32 fragoff)
> {
> - arm_smccc_1_2_smc(&(struct arm_smccc_1_2_regs) {
> + hyp_smccc_1_2_smc(&(struct arm_smccc_1_2_regs) {
> .a0 = FFA_MEM_FRAG_RX,
> .a1 = handle_lo,
> .a2 = handle_hi,
> @@ -196,7 +196,7 @@ static void ffa_mem_frag_rx(struct arm_smccc_1_2_regs *res, u32 handle_lo,
> static void ffa_mem_xfer(struct arm_smccc_1_2_regs *res, u64 func_id, u32 len,
> u32 fraglen)
> {
> - arm_smccc_1_2_smc(&(struct arm_smccc_1_2_regs) {
> + hyp_smccc_1_2_smc(&(struct arm_smccc_1_2_regs) {
> .a0 = func_id,
> .a1 = len,
> .a2 = fraglen,
> @@ -206,7 +206,7 @@ static void ffa_mem_xfer(struct arm_smccc_1_2_regs *res, u64 func_id, u32 len,
> static void ffa_mem_reclaim(struct arm_smccc_1_2_regs *res, u32 handle_lo,
> u32 handle_hi, u32 flags)
> {
> - arm_smccc_1_2_smc(&(struct arm_smccc_1_2_regs) {
> + hyp_smccc_1_2_smc(&(struct arm_smccc_1_2_regs) {
> .a0 = FFA_MEM_RECLAIM,
> .a1 = handle_lo,
> .a2 = handle_hi,
> @@ -216,7 +216,7 @@ static void ffa_mem_reclaim(struct arm_smccc_1_2_regs *res, u32 handle_lo,
>
> static void ffa_retrieve_req(struct arm_smccc_1_2_regs *res, u32 len)
> {
> - arm_smccc_1_2_smc(&(struct arm_smccc_1_2_regs) {
> + hyp_smccc_1_2_smc(&(struct arm_smccc_1_2_regs) {
> .a0 = FFA_FN64_MEM_RETRIEVE_REQ,
> .a1 = len,
> .a2 = len,
> @@ -225,7 +225,7 @@ static void ffa_retrieve_req(struct arm_smccc_1_2_regs *res, u32 len)
>
> static void ffa_rx_release(struct arm_smccc_1_2_regs *res)
> {
> - arm_smccc_1_2_smc(&(struct arm_smccc_1_2_regs) {
> + hyp_smccc_1_2_smc(&(struct arm_smccc_1_2_regs) {
> .a0 = FFA_RX_RELEASE,
> }, res);
> }
> @@ -728,7 +728,7 @@ static int hyp_ffa_post_init(void)
> size_t min_rxtx_sz;
> struct arm_smccc_1_2_regs res;
>
> - arm_smccc_1_2_smc(&(struct arm_smccc_1_2_regs){
> + hyp_smccc_1_2_smc(&(struct arm_smccc_1_2_regs){
> .a0 = FFA_ID_GET,
> }, &res);
> if (res.a0 != FFA_SUCCESS)
> @@ -737,7 +737,7 @@ static int hyp_ffa_post_init(void)
> if (res.a2 != HOST_FFA_ID)
> return -EINVAL;
>
> - arm_smccc_1_2_smc(&(struct arm_smccc_1_2_regs){
> + hyp_smccc_1_2_smc(&(struct arm_smccc_1_2_regs){
> .a0 = FFA_FEATURES,
> .a1 = FFA_FN64_RXTX_MAP,
> }, &res);
> @@ -788,7 +788,7 @@ static void do_ffa_version(struct arm_smccc_1_2_regs *res,
> * first if TEE supports it.
> */
> if (FFA_MINOR_VERSION(ffa_req_version) < FFA_MINOR_VERSION(hyp_ffa_version)) {
> - arm_smccc_1_2_smc(&(struct arm_smccc_1_2_regs) {
> + hyp_smccc_1_2_smc(&(struct arm_smccc_1_2_regs) {
> .a0 = FFA_VERSION,
> .a1 = ffa_req_version,
> }, res);
> @@ -824,7 +824,7 @@ static void do_ffa_part_get(struct arm_smccc_1_2_regs *res,
> goto out_unlock;
> }
>
> - arm_smccc_1_2_smc(&(struct arm_smccc_1_2_regs) {
> + hyp_smccc_1_2_smc(&(struct arm_smccc_1_2_regs) {
> .a0 = FFA_PARTITION_INFO_GET,
> .a1 = uuid0,
> .a2 = uuid1,
> @@ -939,7 +939,7 @@ int hyp_ffa_init(void *pages)
> if (kvm_host_psci_config.smccc_version < ARM_SMCCC_VERSION_1_2)
> return 0;
>
> - arm_smccc_1_2_smc(&(struct arm_smccc_1_2_regs) {
> + hyp_smccc_1_2_smc(&(struct arm_smccc_1_2_regs) {
> .a0 = FFA_VERSION,
> .a1 = FFA_VERSION_1_2,
> }, &res);
> diff --git a/arch/arm64/kvm/hyp/nvhe/hyp-main.c b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
> index 446603cdad7b..ffda4850022f 100644
> --- a/arch/arm64/kvm/hyp/nvhe/hyp-main.c
> +++ b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
> @@ -12,6 +12,7 @@
> #include <asm/kvm_emulate.h>
> #include <asm/kvm_host.h>
> #include <asm/kvm_hyp.h>
> +#include <asm/kvm_hypevents.h>
> #include <asm/kvm_mmu.h>
>
> #include <nvhe/ffa.h>
> @@ -728,7 +729,9 @@ static void handle_host_hcall(struct kvm_cpu_context *host_ctxt)
>
> static void default_host_smc_handler(struct kvm_cpu_context *host_ctxt)
> {
> + trace_hyp_exit(HYP_REASON_SMC);
> __kvm_hyp_host_forward_smc(host_ctxt);
> + trace_hyp_enter(HYP_REASON_SMC);
> }
>
> static void handle_host_smc(struct kvm_cpu_context *host_ctxt)
> @@ -752,18 +755,24 @@ void handle_trap(struct kvm_cpu_context *host_ctxt)
> {
> u64 esr = read_sysreg_el2(SYS_ESR);
>
> +
> switch (ESR_ELx_EC(esr)) {
> case ESR_ELx_EC_HVC64:
> + trace_hyp_enter(HYP_REASON_HVC);
> handle_host_hcall(host_ctxt);
> break;
> case ESR_ELx_EC_SMC64:
> + trace_hyp_enter(HYP_REASON_SMC);
> handle_host_smc(host_ctxt);
> break;
> case ESR_ELx_EC_IABT_LOW:
> case ESR_ELx_EC_DABT_LOW:
> + trace_hyp_enter(HYP_REASON_HOST_ABORT);
> handle_host_mem_abort(host_ctxt);
> break;
> default:
> BUG();
> }
> +
> + trace_hyp_exit(HYP_REASON_ERET_HOST);
> }
> diff --git a/arch/arm64/kvm/hyp/nvhe/psci-relay.c b/arch/arm64/kvm/hyp/nvhe/psci-relay.c
> index c3e196fb8b18..58658e09c372 100644
> --- a/arch/arm64/kvm/hyp/nvhe/psci-relay.c
> +++ b/arch/arm64/kvm/hyp/nvhe/psci-relay.c
> @@ -6,11 +6,12 @@
>
> #include <asm/kvm_asm.h>
> #include <asm/kvm_hyp.h>
> +#include <asm/kvm_hypevents.h>
> #include <asm/kvm_mmu.h>
> -#include <linux/arm-smccc.h>
> #include <linux/kvm_host.h>
> #include <uapi/linux/psci.h>
>
> +#include <nvhe/arm-smccc.h>
> #include <nvhe/memory.h>
> #include <nvhe/trap_handler.h>
>
> @@ -65,7 +66,7 @@ static unsigned long psci_call(unsigned long fn, unsigned long arg0,
> {
> struct arm_smccc_res res;
>
> - arm_smccc_1_1_smc(fn, arg0, arg1, arg2, &res);
> + hyp_smccc_1_1_smc(fn, arg0, arg1, arg2, &res);
> return res.a0;
> }
>
> @@ -205,6 +206,7 @@ asmlinkage void __noreturn __kvm_host_psci_cpu_entry(bool is_cpu_on)
> struct psci_boot_args *boot_args;
> struct kvm_cpu_context *host_ctxt;
>
> + trace_hyp_enter(HYP_REASON_PSCI);
> host_ctxt = host_data_ptr(host_ctxt);
>
> if (is_cpu_on)
> @@ -221,6 +223,7 @@ asmlinkage void __noreturn __kvm_host_psci_cpu_entry(bool is_cpu_on)
> write_sysreg_el1(INIT_SCTLR_EL1_MMU_OFF, SYS_SCTLR);
> write_sysreg(INIT_PSTATE_EL1, SPSR_EL2);
>
> + trace_hyp_exit(HYP_REASON_PSCI);
> __host_enter(host_ctxt);
> }
>
> diff --git a/arch/arm64/kvm/hyp/nvhe/switch.c b/arch/arm64/kvm/hyp/nvhe/switch.c
> index d3b9ec8a7c28..3dc2bbab4bfc 100644
> --- a/arch/arm64/kvm/hyp/nvhe/switch.c
> +++ b/arch/arm64/kvm/hyp/nvhe/switch.c
> @@ -7,7 +7,6 @@
> #include <hyp/switch.h>
> #include <hyp/sysreg-sr.h>
>
> -#include <linux/arm-smccc.h>
> #include <linux/kvm_host.h>
> #include <linux/types.h>
> #include <linux/jump_label.h>
> @@ -21,6 +20,7 @@
> #include <asm/kvm_asm.h>
> #include <asm/kvm_emulate.h>
> #include <asm/kvm_hyp.h>
> +#include <asm/kvm_hypevents.h>
> #include <asm/kvm_mmu.h>
> #include <asm/fpsimd.h>
> #include <asm/debug-monitors.h>
> @@ -308,10 +308,13 @@ int __kvm_vcpu_run(struct kvm_vcpu *vcpu)
> __debug_switch_to_guest(vcpu);
>
> do {
> + trace_hyp_exit(HYP_REASON_ERET_GUEST);
> +
> /* Jump in the fire! */
> exit_code = __guest_enter(vcpu);
>
> /* And we're baaack! */
> + trace_hyp_enter(HYP_REASON_GUEST_EXIT);

nit: seeing these two events back to back makes me think that one of
them is misnamed. Either the first should be GUEST_ENTER, or the
second should be GUEST_EXCEPT... Preference for the former.

> } while (fixup_guest_exit(vcpu, &exit_code));
>
> __sysreg_save_state_nvhe(guest_ctxt);
> diff --git a/arch/arm64/kvm/hyp_trace.c b/arch/arm64/kvm/hyp_trace.c
> index 0144cd26703e..1ad6a55ba95c 100644
> --- a/arch/arm64/kvm/hyp_trace.c
> +++ b/arch/arm64/kvm/hyp_trace.c
> @@ -364,8 +364,26 @@ static struct trace_remote_callbacks trace_remote_callbacks = {
> .enable_event = hyp_trace_enable_event,
> };
>
> +static const char *__hyp_enter_exit_reason_str(u8 reason);
> +
> #include <asm/kvm_define_hypevents.h>
>
> +static const char *__hyp_enter_exit_reason_str(u8 reason)

That's one ugly hack... :-(

> +{
> + static const char strs[][12] = {
> + "smc",
> + "hvc",
> + "psci",
> + "host_abort",
> + "guest_exit",
> + "eret_host",
> + "eret_guest",
> + "unknown",
> + };
> +
> + return strs[min(reason, HYP_REASON_UNKNOWN)];
> +}
> +
> static void __init hyp_trace_init_events(void)
> {
> struct hyp_event_id *hyp_event_id = __hyp_event_ids_start;

Thanks,

M.

--
Without deviation from the norm, progress is not possible.