Re: [PATCH v2] RISC-V: KVM: Add arch-specific tracepoints

On Thu, Jul 30, 2026 at 12:27 PM Yuhang.Chen <[email protected]> wrote:
>
> Add RISC-V KVM tracepoints for events that are useful when debugging
> guest exits and in-kernel emulation paths. The existing kvm_entry and
> kvm_exit tracepoints are kept, with the kvm_entry PC format fixed to use
> zero-padded hexadecimal output.
>
> The newly added tracepoints cover:
>
> - kvm_vcpu_exit for synchronous guest traps
> - kvm_vcpu_irq for VS-mode interrupt set/clear
> - kvm_mmio_emulate for MMIO load/store emulation
>
> kvm_vcpu_exit reports the full trap context (sepc/scause/stval/htval/
> htinst) so userspace can filter by scause, and is placed after the
> interrupt early-return so it fires only for synchronous traps.
> kvm_vcpu_irq covers every set/unset_interrupt() caller from a single
> place.
>
> Example trace output:
>
> kvm_vcpu_exit:
> VCPU: 0, SEPC: 0x80200000, SCAUSE: 0x17,
> STVAL: 0x10000000, HTVAL: 0x4000000, HTINST: 0x2023
>
> kvm_mmio_emulate:
> VCPU: 0, Store MMIO at 0x10000000, len 4, insn 0x2023, sepc 0x80200000
>
> kvm_vcpu_irq:
> VCPU: 0, IRQ: 10, level: 1
>
> Testing:
>
> A QEMU-based test program was used to exercise:
>
> - Guest page faults
> - MMIO emulation
> - IRQ injection
>
> Verified trace output generation for:
>
> - kvm_vcpu_exit
> - kvm_vcpu_irq
> - kvm_mmio_emulate
>
> Assisted-by: YuanSheng:deepseek-v4-pro
> Co-developed-by: Quan Zhou <[email protected]>
> Signed-off-by: Quan Zhou <[email protected]>
> Signed-off-by: Yuhang.Chen <[email protected]>

LGTM.

Reviewed-by: Anup Patel <[email protected]>

Queued this patch for Linux-7.3

Thanks,
Anup

> ---
> Changes in v2, per Anup Patel's review [1]:
>
> - Replace the per-cause tracepoints kvm_guest_fault, kvm_sbi_ecall,
>   kvm_wait_riscv and kvm_csr_access with a single generic kvm_vcpu_exit
>   tracepoint that reports the full trap context (sepc/scause/stval/
>   htval/htinst).
> - Replace kvm_irq_line and kvm_timer_update_irq with a single generic
>   kvm_vcpu_irq tracepoint covering all set/unset_interrupt() callers.
> - Keep kvm_mmio_emulate.
> - Drop the now-unused trace.h includes from vcpu_sbi.c, vcpu_timer.c
>   and vm.c.
>
> [1] https://lore.kernel.org/all/CAAhSdy2Qa2DGFzb27MgmoH5Pf1BOrgwaZBqP__U9eejs5-5Bsw@mail.gmail.com/
> ---
>  arch/riscv/kvm/trace.h     | 81 +++++++++++++++++++++++++++++++++++++-
>  arch/riscv/kvm/vcpu.c      |  4 ++
>  arch/riscv/kvm/vcpu_exit.c |  4 ++
>  arch/riscv/kvm/vcpu_insn.c | 13 +++++-
>  4 files changed, 98 insertions(+), 4 deletions(-)
>
> diff --git a/arch/riscv/kvm/trace.h b/arch/riscv/kvm/trace.h
> index 3d54175d805c..23a5fd1b686e 100644
> --- a/arch/riscv/kvm/trace.h
> +++ b/arch/riscv/kvm/trace.h
> @@ -25,7 +25,7 @@ TRACE_EVENT(kvm_entry,
>                 __entry->pc     = vcpu->arch.guest_context.sepc;
>         ),
>
> -       TP_printk("PC: 0x016%lx", __entry->pc)
> +       TP_printk("PC: 0x%016lx", __entry->pc)
>  );
>
>  TRACE_EVENT(kvm_exit,
> @@ -56,7 +56,84 @@ TRACE_EVENT(kvm_exit,
>                 __entry->htinst)
>  );
>
> -#endif /* _TRACE_RSICV_KVM_H */
> +TRACE_EVENT(kvm_mmio_emulate,
> +       TP_PROTO(unsigned long vcpu_id, unsigned long sepc, unsigned long insn,
> +                unsigned long fault_addr, bool write, int len),
> +       TP_ARGS(vcpu_id, sepc, insn, fault_addr, write, len),
> +
> +       TP_STRUCT__entry(
> +               __field(unsigned long, vcpu_id)
> +               __field(unsigned long, sepc)
> +               __field(unsigned long, insn)
> +               __field(unsigned long, fault_addr)
> +               __field(bool, write)
> +               __field(int, len)
> +       ),
> +
> +       TP_fast_assign(
> +               __entry->vcpu_id        = vcpu_id;
> +               __entry->sepc           = sepc;
> +               __entry->insn           = insn;
> +               __entry->fault_addr     = fault_addr;
> +               __entry->write          = write;
> +               __entry->len            = len;
> +       ),
> +
> +       TP_printk("VCPU: %lu, %s MMIO at 0x%lx, len %d, insn 0x%lx, sepc 0x%lx",
> +                 __entry->vcpu_id, __entry->write ? "Store" : "Load",
> +                 __entry->fault_addr, __entry->len, __entry->insn,
> +                 __entry->sepc)
> +);
> +
> +TRACE_EVENT(kvm_vcpu_exit,
> +       TP_PROTO(unsigned long vcpu_id, unsigned long sepc, unsigned long scause,
> +                unsigned long stval, unsigned long htval, unsigned long htinst),
> +       TP_ARGS(vcpu_id, sepc, scause, stval, htval, htinst),
> +
> +       TP_STRUCT__entry(
> +               __field(unsigned long, vcpu_id)
> +               __field(unsigned long, sepc)
> +               __field(unsigned long, scause)
> +               __field(unsigned long, stval)
> +               __field(unsigned long, htval)
> +               __field(unsigned long, htinst)
> +       ),
> +
> +       TP_fast_assign(
> +               __entry->vcpu_id        = vcpu_id;
> +               __entry->sepc           = sepc;
> +               __entry->scause         = scause;
> +               __entry->stval          = stval;
> +               __entry->htval          = htval;
> +               __entry->htinst         = htinst;
> +       ),
> +
> +       TP_printk("VCPU: %lu, SEPC: 0x%lx, SCAUSE: 0x%lx, STVAL: 0x%lx, HTVAL: 0x%lx, HTINST: 0x%lx",
> +                 __entry->vcpu_id, __entry->sepc, __entry->scause,
> +                 __entry->stval, __entry->htval, __entry->htinst)
> +);
> +
> +TRACE_EVENT(kvm_vcpu_irq,
> +       TP_PROTO(unsigned long vcpu_id, unsigned int irq, int level),
> +       TP_ARGS(vcpu_id, irq, level),
> +
> +       TP_STRUCT__entry(
> +               __field(unsigned long, vcpu_id)
> +               __field(unsigned int, irq)
> +               __field(int, level)
> +       ),
> +
> +       TP_fast_assign(
> +               __entry->vcpu_id        = vcpu_id;
> +               __entry->irq            = irq;
> +               __entry->level          = level;
> +       ),
> +
> +       TP_printk("VCPU: %lu, IRQ: %u, level: %d",
> +                 __entry->vcpu_id, __entry->irq, __entry->level)
> +);
> +
> +#endif /* _TRACE_KVM_H */
>
>  #undef TRACE_INCLUDE_PATH
>  #define TRACE_INCLUDE_PATH .
> diff --git a/arch/riscv/kvm/vcpu.c b/arch/riscv/kvm/vcpu.c
> index 977e36ab83d3..c0556cb4caa5 100644
> --- a/arch/riscv/kvm/vcpu.c
> +++ b/arch/riscv/kvm/vcpu.c
> @@ -439,6 +439,8 @@ int kvm_riscv_vcpu_set_interrupt(struct kvm_vcpu *vcpu, unsigned int irq)
>         __set_bit(irq, vcpu->arch.irqs_pending_mask);
>         raw_spin_unlock_irqrestore(&vcpu->arch.irqs_pending_lock, flags);
>
> +       trace_kvm_vcpu_irq(vcpu->vcpu_id, irq, 1);
> +
>         kvm_vcpu_kick(vcpu);
>
>         return 0;
> @@ -465,6 +467,8 @@ int kvm_riscv_vcpu_unset_interrupt(struct kvm_vcpu *vcpu, unsigned int irq)
>         __set_bit(irq, vcpu->arch.irqs_pending_mask);
>         raw_spin_unlock_irqrestore(&vcpu->arch.irqs_pending_lock, flags);
>
> +       trace_kvm_vcpu_irq(vcpu->vcpu_id, irq, 0);
> +
>         return 0;
>  }
>
> diff --git a/arch/riscv/kvm/vcpu_exit.c b/arch/riscv/kvm/vcpu_exit.c
> index 6c8530b9f29e..d03c6e82b1bc 100644
> --- a/arch/riscv/kvm/vcpu_exit.c
> +++ b/arch/riscv/kvm/vcpu_exit.c
> @@ -11,6 +11,7 @@
>  #include <asm/insn-def.h>
>  #include <asm/kvm_mmu.h>
>  #include <asm/kvm_nacl.h>
> +#include "trace.h"
>
>  static int gstage_page_fault(struct kvm_vcpu *vcpu, struct kvm_run *run,
>                              struct kvm_cpu_trap *trap)
> @@ -212,6 +213,9 @@ int kvm_riscv_vcpu_exit(struct kvm_vcpu *vcpu, struct kvm_run *run,
>         if (trap->scause & CAUSE_IRQ_FLAG)
>                 return 1;
>
> +       trace_kvm_vcpu_exit(vcpu->vcpu_id, trap->sepc, trap->scause,
> +                           trap->stval, trap->htval, trap->htinst);
> +
>         /* Handle guest traps */
>         ret = -EFAULT;
>         run->exit_reason = KVM_EXIT_UNKNOWN;
> diff --git a/arch/riscv/kvm/vcpu_insn.c b/arch/riscv/kvm/vcpu_insn.c
> index f09f9251d1f0..ef2a827811f3 100644
> --- a/arch/riscv/kvm/vcpu_insn.c
> +++ b/arch/riscv/kvm/vcpu_insn.c
> @@ -9,6 +9,7 @@
>
>  #include <asm/cpufeature.h>
>  #include <asm/insn.h>
> +#include "trace.h"
>
>  struct insn_func {
>         unsigned long mask;
> @@ -375,7 +376,7 @@ int kvm_riscv_vcpu_mmio_load(struct kvm_vcpu *vcpu, struct kvm_run *run,
>                              unsigned long htinst)
>  {
>         u8 data_buf[8];
> -       unsigned long insn;
> +       unsigned long insn, raw_insn;
>         int shift = 0, len = 0, insn_len = 0;
>         struct kvm_cpu_trap utrap = { 0 };
>         struct kvm_cpu_context *ct = &vcpu->arch.guest_context;
> @@ -405,6 +406,7 @@ int kvm_riscv_vcpu_mmio_load(struct kvm_vcpu *vcpu, struct kvm_run *run,
>                 }
>                 insn_len = INSN_LEN(insn);
>         }
> +       raw_insn = insn;
>
>         /* Decode length of MMIO and shift */
>         if ((insn & INSN_MASK_LW) == INSN_MATCH_LW) {
> @@ -453,6 +455,9 @@ int kvm_riscv_vcpu_mmio_load(struct kvm_vcpu *vcpu, struct kvm_run *run,
>         if (fault_addr & (len - 1))
>                 return -EIO;
>
> +       trace_kvm_mmio_emulate(vcpu->vcpu_id, ct->sepc, raw_insn, fault_addr,
> +                              false, len);
> +
>         /* Save instruction decode info */
>         vcpu->arch.mmio_decode.insn = insn;
>         vcpu->arch.mmio_decode.insn_len = insn_len;
> @@ -502,7 +507,7 @@ int kvm_riscv_vcpu_mmio_store(struct kvm_vcpu *vcpu, struct kvm_run *run,
>         u32 data32;
>         u64 data64;
>         ulong data;
> -       unsigned long insn;
> +       unsigned long insn, raw_insn;
>         int len = 0, insn_len = 0;
>         struct kvm_cpu_trap utrap = { 0 };
>         struct kvm_cpu_context *ct = &vcpu->arch.guest_context;
> @@ -532,6 +537,7 @@ int kvm_riscv_vcpu_mmio_store(struct kvm_vcpu *vcpu, struct kvm_run *run,
>                 }
>                 insn_len = INSN_LEN(insn);
>         }
> +       raw_insn = insn;
>
>         data = GET_RS2(insn, &vcpu->arch.guest_context);
>         data8 = data16 = data32 = data64 = data;
> @@ -570,6 +576,9 @@ int kvm_riscv_vcpu_mmio_store(struct kvm_vcpu *vcpu, struct kvm_run *run,
>         if (fault_addr & (len - 1))
>                 return -EIO;
>
> +       trace_kvm_mmio_emulate(vcpu->vcpu_id, ct->sepc, raw_insn, fault_addr,
> +                              true, len);
> +
>         /* Save instruction decode info */
>         vcpu->arch.mmio_decode.insn = insn;
>         vcpu->arch.mmio_decode.insn_len = insn_len;
> --
> 2.34.1
>

_______________________________________________
linux-riscv mailing list
[email protected]
http://lists.infradead.org/mailman/listinfo/linux-riscv