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

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Message-ID: <CAK9=C2WwD+RMUmO8SR-bBMfEJLGfd4pMswQx19URLng20Mui-g@mail.gmail.com>
Date: Tue, 24 Dec 2024 08:34:53 +0530
From: Anup Patel <apatel@...tanamicro.com>
To: Atish Kumar Patra <atishp@...osinc.com>
Cc: Anup Patel <anup@...infault.org>, 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 Tue, Dec 24, 2024 at 6:58 AM Atish Kumar Patra <atishp@...osinc.com> wrote:
>
> 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.

Yes, please send v2.

Regards,
Anup

>
> > >
> > > 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
> > >
>