Re: [PATCH v2 06/13] RISC-V: KVM: Add SBI STA info to vcpu_arch

[Andrew Jones <ajones@ventanamicro.com>]

On Fri, Dec 15, 2023 at 02:37:32PM +0530, Anup Patel wrote:
> On Thu, Dec 14, 2023 at 3:46 PM Andrew Jones <ajones@ventanamicro.com> wrote:
> >
> > KVM's implementation of SBI STA needs to track the address of each
> > VCPU's steal-time shared memory region as well as the amount of
> > stolen time. Add a structure to vcpu_arch to contain this state
> > and make sure that the address is always set to INVALID_GPA on
> > vcpu reset. And, of course, ensure KVM won't try to update steal-
> > time when the shared memory address is invalid.
> >
> > Signed-off-by: Andrew Jones <ajones@ventanamicro.com>
> > ---
> >  arch/riscv/include/asm/kvm_host.h | 6 ++++++
> >  arch/riscv/kvm/vcpu.c             | 2 ++
> >  arch/riscv/kvm/vcpu_sbi_sta.c     | 4 ++++
> >  3 files changed, 12 insertions(+)
> >
> > diff --git a/arch/riscv/include/asm/kvm_host.h b/arch/riscv/include/asm/kvm_host.h
> > index 230b82c3118d..b10026fb6412 100644
> > --- a/arch/riscv/include/asm/kvm_host.h
> > +++ b/arch/riscv/include/asm/kvm_host.h
> > @@ -263,6 +263,12 @@ struct kvm_vcpu_arch {
> >
> >         /* 'static' configurations which are set only once */
> >         struct kvm_vcpu_config cfg;
> > +
> > +       /* SBI steal-time accounting */
> > +       struct {
> > +               gpa_t shmem;
> > +               u64 last_steal;
> > +       } sta;
> >  };
> >
> >  static inline void kvm_arch_sync_events(struct kvm *kvm) {}
> > diff --git a/arch/riscv/kvm/vcpu.c b/arch/riscv/kvm/vcpu.c
> > index 6995b8b641e4..fec4f5fd0fa7 100644
> > --- a/arch/riscv/kvm/vcpu.c
> > +++ b/arch/riscv/kvm/vcpu.c
> > @@ -83,6 +83,8 @@ static void kvm_riscv_reset_vcpu(struct kvm_vcpu *vcpu)
> >         vcpu->arch.hfence_tail = 0;
> >         memset(vcpu->arch.hfence_queue, 0, sizeof(vcpu->arch.hfence_queue));
> >
> > +       vcpu->arch.sta.shmem = INVALID_GPA;
> > +
> 
> I think we should also set last_steal to zero as well.
> 
> Also, let's add kvm_riscv_vcpu_sbi_sta_reset() in vcpu_sbi_sta.c
> to reset VCPU STA state.

Will do.

> 
> >         /* Reset the guest CSRs for hotplug usecase */
> >         if (loaded)
> >                 kvm_arch_vcpu_load(vcpu, smp_processor_id());
> > diff --git a/arch/riscv/kvm/vcpu_sbi_sta.c b/arch/riscv/kvm/vcpu_sbi_sta.c
> > index e28351c9488b..157c199be0b4 100644
> > --- a/arch/riscv/kvm/vcpu_sbi_sta.c
> > +++ b/arch/riscv/kvm/vcpu_sbi_sta.c
> > @@ -10,6 +10,10 @@
> >
> >  void kvm_riscv_vcpu_record_steal_time(struct kvm_vcpu *vcpu)
> >  {
> > +       gpa_t shmem = vcpu->arch.sta.shmem;
> > +
> > +       if (shmem == INVALID_GPA)
> > +               return;
> >  }
> >
> >  static int kvm_sbi_sta_steal_time_set_shmem(struct kvm_vcpu *vcpu)
> > --
> > 2.43.0
> >
> 
> Apart from the above, it looks good to me.
> 
> Reviewed-by: Anup Patel <anup@brainfault.org>

Thanks,
drew

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