linux-kernel - Re: [PATCH 3/3] RISC-V: KVM: Add new exit statstics for redirected traps

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Message-ID: <CAAhSdy24K3pkOR25Rbcvw6pRWXrKXdy0CH9CLeG77EqQRZTDnQ@mail.gmail.com>
Date: Mon, 23 Dec 2024 19:49:22 +0530
From: Anup Patel <anup@...infault.org>
To: Atish Patra <atishp@...osinc.com>
Cc: Atish Patra <atishp@...shpatra.org>, Paul Walmsley <paul.walmsley@...ive.com>, 
	Palmer Dabbelt <palmer@...belt.com>, kvm@...r.kernel.org, kvm-riscv@...ts.infradead.org, 
	linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] RISC-V: KVM: Add new exit statstics for redirected traps

On Fri, Dec 13, 2024 at 2:27 AM Atish Patra <atishp@...osinc.com> wrote:
>
> Currently, kvm doesn't delegate the few traps such as misaligned
> load/store, illegal instruction and load/store access faults because it
> is not expected to occur in the guest very frequent. Thus, kvm gets a
> chance to act upon it or collect statstics about it before redirecting
> the traps to the guest.
>
> We can collect both guest and host visible statistics during the traps.
> Enable them so that both guest and host can collect the stats about
> them if required.

s/We can collect .../Collect .../

>
> Signed-off-by: Atish Patra <atishp@...osinc.com>

Otherwise, it looks good to me.

Reviewed-by: Anup Patel <anup@...infault.org>

Regards,
Anup

> ---
>  arch/riscv/include/asm/kvm_host.h | 5 +++++
>  arch/riscv/kvm/vcpu.c             | 7 ++++++-
>  arch/riscv/kvm/vcpu_exit.c        | 5 +++++
>  3 files changed, 16 insertions(+), 1 deletion(-)
>
> diff --git a/arch/riscv/include/asm/kvm_host.h b/arch/riscv/include/asm/kvm_host.h
> index 35eab6e0f4ae..cc33e35cd628 100644
> --- a/arch/riscv/include/asm/kvm_host.h
> +++ b/arch/riscv/include/asm/kvm_host.h
> @@ -87,6 +87,11 @@ struct kvm_vcpu_stat {
>         u64 csr_exit_kernel;
>         u64 signal_exits;
>         u64 exits;
> +       u64 instr_illegal_exits;
> +       u64 load_misaligned_exits;
> +       u64 store_misaligned_exits;
> +       u64 load_access_exits;
> +       u64 store_access_exits;
>  };
>
>  struct kvm_arch_memory_slot {
> diff --git a/arch/riscv/kvm/vcpu.c b/arch/riscv/kvm/vcpu.c
> index e048dcc6e65e..60d684c76c58 100644
> --- a/arch/riscv/kvm/vcpu.c
> +++ b/arch/riscv/kvm/vcpu.c
> @@ -34,7 +34,12 @@ const struct _kvm_stats_desc kvm_vcpu_stats_desc[] = {
>         STATS_DESC_COUNTER(VCPU, csr_exit_user),
>         STATS_DESC_COUNTER(VCPU, csr_exit_kernel),
>         STATS_DESC_COUNTER(VCPU, signal_exits),
> -       STATS_DESC_COUNTER(VCPU, exits)
> +       STATS_DESC_COUNTER(VCPU, exits),
> +       STATS_DESC_COUNTER(VCPU, instr_illegal_exits),
> +       STATS_DESC_COUNTER(VCPU, load_misaligned_exits),
> +       STATS_DESC_COUNTER(VCPU, store_misaligned_exits),
> +       STATS_DESC_COUNTER(VCPU, load_access_exits),
> +       STATS_DESC_COUNTER(VCPU, store_access_exits),
>  };
>
>  const struct kvm_stats_header kvm_vcpu_stats_header = {
> diff --git a/arch/riscv/kvm/vcpu_exit.c b/arch/riscv/kvm/vcpu_exit.c
> index acdcd619797e..6e0c18412795 100644
> --- a/arch/riscv/kvm/vcpu_exit.c
> +++ b/arch/riscv/kvm/vcpu_exit.c
> @@ -195,22 +195,27 @@ int kvm_riscv_vcpu_exit(struct kvm_vcpu *vcpu, struct kvm_run *run,
>         switch (trap->scause) {
>         case EXC_INST_ILLEGAL:
>                 kvm_riscv_vcpu_pmu_incr_fw(vcpu, SBI_PMU_FW_ILLEGAL_INSN);
> +               vcpu->stat.instr_illegal_exits++;
>                 ret = vcpu_redirect(vcpu, trap);
>                 break;
>         case EXC_LOAD_MISALIGNED:
>                 kvm_riscv_vcpu_pmu_incr_fw(vcpu, SBI_PMU_FW_MISALIGNED_LOAD);
> +               vcpu->stat.load_misaligned_exits++;
>                 ret = vcpu_redirect(vcpu, trap);
>                 break;
>         case EXC_STORE_MISALIGNED:
>                 kvm_riscv_vcpu_pmu_incr_fw(vcpu, SBI_PMU_FW_MISALIGNED_STORE);
> +               vcpu->stat.store_misaligned_exits++;
>                 ret = vcpu_redirect(vcpu, trap);
>                 break;
>         case EXC_LOAD_ACCESS:
>                 kvm_riscv_vcpu_pmu_incr_fw(vcpu, SBI_PMU_FW_ACCESS_LOAD);
> +               vcpu->stat.load_access_exits++;
>                 ret = vcpu_redirect(vcpu, trap);
>                 break;
>         case EXC_STORE_ACCESS:
>                 kvm_riscv_vcpu_pmu_incr_fw(vcpu, SBI_PMU_FW_ACCESS_STORE);
> +               vcpu->stat.store_access_exits++;
>                 ret = vcpu_redirect(vcpu, trap);
>                 break;
>         case EXC_INST_ACCESS:
>
> --
> 2.34.1
>