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

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Message-ID: <CAHBxVyH3eX0o66398+L09RKriudDC90M_7wzsRrQZ+42f4JOVQ@mail.gmail.com>
Date: Mon, 23 Dec 2024 17:28:28 -0800
From: Atish Kumar Patra <atishp@...osinc.com>
To: Anup Patel <anup@...infault.org>
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 Mon, Dec 23, 2024 at 6:19 AM Anup Patel <anup@...infault.org> wrote:
>
> 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 .../
>

Let me know if I should send a v2. I noticed a couple of other typos
in the commit text as well.

> >
> > 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
> >