linux-kernel - Re: [PATCH v2 02/11] RISC-V: KVM: Define a probe function for SBI extension data structures

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Date:   Thu, 12 Jan 2023 10:19:46 -0800
From:   Atish Kumar Patra <atishp@...osinc.com>
To:     Andrew Jones <ajones@...tanamicro.com>
Cc:     linux-kernel@...r.kernel.org, Anup Patel <anup@...infault.org>,
        Atish Patra <atishp@...shpatra.org>,
        Guo Ren <guoren@...nel.org>, kvm-riscv@...ts.infradead.org,
        kvm@...r.kernel.org, linux-riscv@...ts.infradead.org,
        Mark Rutland <mark.rutland@....com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Sergey Matyukevich <sergey.matyukevich@...tacore.com>,
        Eric Lin <eric.lin@...ive.com>, Will Deacon <will@...nel.org>
Subject: Re: [PATCH v2 02/11] RISC-V: KVM: Define a probe function for SBI
 extension data structures

On Thu, Jan 12, 2023 at 2:21 AM Andrew Jones <ajones@...tanamicro.com> wrote:
>
> On Thu, Dec 15, 2022 at 09:00:37AM -0800, Atish Patra wrote:
> > Currently the probe function just checks if an SBI extension is
> > registered or not. However, the extension may not want to advertise
> > itself depending on some other condition.
> > An additional extension specific probe function will allow
> > extensions to decide if they want to be advertised to the caller or
> > not. Any extension that does not require additional dependency checks
> > can avoid implementing this function.
> >
> > Signed-off-by: Atish Patra <atishp@...osinc.com>
> > ---
> >  arch/riscv/include/asm/kvm_vcpu_sbi.h |  3 +++
> >  arch/riscv/kvm/vcpu_sbi_base.c        | 13 +++++++++++--
> >  2 files changed, 14 insertions(+), 2 deletions(-)
> >
> > diff --git a/arch/riscv/include/asm/kvm_vcpu_sbi.h b/arch/riscv/include/asm/kvm_vcpu_sbi.h
> > index f79478a..61dac1b 100644
> > --- a/arch/riscv/include/asm/kvm_vcpu_sbi.h
> > +++ b/arch/riscv/include/asm/kvm_vcpu_sbi.h
> > @@ -29,6 +29,9 @@ struct kvm_vcpu_sbi_extension {
> >       int (*handler)(struct kvm_vcpu *vcpu, struct kvm_run *run,
> >                      unsigned long *out_val, struct kvm_cpu_trap *utrap,
> >                      bool *exit);
> > +
> > +     /* Extension specific probe function */
> > +     unsigned long (*probe)(struct kvm_vcpu *vcpu, unsigned long extid);
>
> It doesn't seem like the extid parameter should be necessary since the
> probe function is specific to the extension, but it doesn't hurt either.
>

Yeah. You are correct. I will drop it. Thanks.

> >  };
> >
> >  void kvm_riscv_vcpu_sbi_forward(struct kvm_vcpu *vcpu, struct kvm_run *run);
> > diff --git a/arch/riscv/kvm/vcpu_sbi_base.c b/arch/riscv/kvm/vcpu_sbi_base.c
> > index 5d65c63..89e2415 100644
> > --- a/arch/riscv/kvm/vcpu_sbi_base.c
> > +++ b/arch/riscv/kvm/vcpu_sbi_base.c
> > @@ -19,6 +19,7 @@ static int kvm_sbi_ext_base_handler(struct kvm_vcpu *vcpu, struct kvm_run *run,
> >  {
> >       int ret = 0;
> >       struct kvm_cpu_context *cp = &vcpu->arch.guest_context;
> > +     const struct kvm_vcpu_sbi_extension *sbi_ext;
> >
> >       switch (cp->a6) {
> >       case SBI_EXT_BASE_GET_SPEC_VERSION:
> > @@ -43,8 +44,16 @@ static int kvm_sbi_ext_base_handler(struct kvm_vcpu *vcpu, struct kvm_run *run,
> >                        */
> >                       kvm_riscv_vcpu_sbi_forward(vcpu, run);
> >                       *exit = true;
> > -             } else
> > -                     *out_val = kvm_vcpu_sbi_find_ext(cp->a0) ? 1 : 0;
> > +             } else {
> > +                     sbi_ext = kvm_vcpu_sbi_find_ext(cp->a0);
> > +                     if (sbi_ext) {
> > +                             if (sbi_ext->probe)
> > +                                     *out_val = sbi_ext->probe(vcpu, cp->a0);
> > +                             else
> > +                                     *out_val = 1;
> > +                     } else
> > +                             *out_val = 0;
> > +             }
> >               break;
> >       case SBI_EXT_BASE_GET_MVENDORID:
> >               *out_val = vcpu->arch.mvendorid;
> > --
> > 2.25.1
> >
>
> Reviewed-by: Andrew Jones <ajones@...tanamicro.com>