Re: [PATCH 4/4] KVM: riscv: selftests: Selectively filter-out AIA registers

[Anup Patel]

On Wed, Sep 20, 2023 at 1:43 AM Atish Patra <atishp@xxxxxxxxxxxxxx> wrote:
>
> On Mon, Sep 18, 2023 at 11:07 AM Anup Patel <apatel@xxxxxxxxxxxxxxxx> wrote:
> >
> > Currently the AIA ONE_REG registers are reported by get-reg-list
> > as new registers for various vcpu_reg_list configs whenever Ssaia
> > is available on the host because Ssaia extension can only be
> > disabled by Smstateen extension which is not always available.
> >
> > To tackle this, we should filter-out AIA ONE_REG registers only
> > when Ssaia can't be disabled for a VCPU.
> >
> > Fixes: 477069398ed6 ("KVM: riscv: selftests: Add get-reg-list test")
> > Signed-off-by: Anup Patel <apatel@xxxxxxxxxxxxxxxx>
> > ---
> >  .../selftests/kvm/riscv/get-reg-list.c        | 23 +++++++++++++++++--
> >  1 file changed, 21 insertions(+), 2 deletions(-)
> >
> > diff --git a/tools/testing/selftests/kvm/riscv/get-reg-list.c b/tools/testing/selftests/kvm/riscv/get-reg-list.c
> > index 76c0ad11e423..85907c86b835 100644
> > --- a/tools/testing/selftests/kvm/riscv/get-reg-list.c
> > +++ b/tools/testing/selftests/kvm/riscv/get-reg-list.c
> > @@ -12,6 +12,8 @@
> >
> >  #define REG_MASK (KVM_REG_ARCH_MASK | KVM_REG_SIZE_MASK)
> >
> > +static bool isa_ext_cant_disable[KVM_RISCV_ISA_EXT_MAX];
> > +
> >  bool filter_reg(__u64 reg)
> >  {
> >         switch (reg & ~REG_MASK) {
> > @@ -48,6 +50,15 @@ bool filter_reg(__u64 reg)
> >         case KVM_REG_RISCV_ISA_EXT | KVM_RISCV_ISA_EXT_ZIFENCEI:
> >         case KVM_REG_RISCV_ISA_EXT | KVM_RISCV_ISA_EXT_ZIHPM:
> >                 return true;
> > +       /* AIA registers are always available when Ssaia can't be disabled */
> > +       case KVM_REG_RISCV_CSR | KVM_REG_RISCV_CSR_AIA | KVM_REG_RISCV_CSR_AIA_REG(siselect):
> > +       case KVM_REG_RISCV_CSR | KVM_REG_RISCV_CSR_AIA | KVM_REG_RISCV_CSR_AIA_REG(iprio1):
> > +       case KVM_REG_RISCV_CSR | KVM_REG_RISCV_CSR_AIA | KVM_REG_RISCV_CSR_AIA_REG(iprio2):
> > +       case KVM_REG_RISCV_CSR | KVM_REG_RISCV_CSR_AIA | KVM_REG_RISCV_CSR_AIA_REG(sieh):
> > +       case KVM_REG_RISCV_CSR | KVM_REG_RISCV_CSR_AIA | KVM_REG_RISCV_CSR_AIA_REG(siph):
> > +       case KVM_REG_RISCV_CSR | KVM_REG_RISCV_CSR_AIA | KVM_REG_RISCV_CSR_AIA_REG(iprio1h):
> > +       case KVM_REG_RISCV_CSR | KVM_REG_RISCV_CSR_AIA | KVM_REG_RISCV_CSR_AIA_REG(iprio2h):
> > +               return isa_ext_cant_disable[KVM_RISCV_ISA_EXT_SSAIA] ? true : false;
>
> Ahh I guess. you do need the switch case for AIA CSRs but for ISA
> extensions can be avoided as it is contiguous.

Fow now, let's leave it as-is because this way get-reg-list will
complain if some new ONE_REG register is missed out.

>
> >         default:
> >                 break;
> >         }
> > @@ -71,14 +82,22 @@ static inline bool vcpu_has_ext(struct kvm_vcpu *vcpu, int ext)
> >
> >  void finalize_vcpu(struct kvm_vcpu *vcpu, struct vcpu_reg_list *c)
> >  {
> > +       int rc;
> >         struct vcpu_reg_sublist *s;
> > +       unsigned long isa_ext_state[KVM_RISCV_ISA_EXT_MAX] = { 0 };
> > +
> > +       for (int i = 0; i < KVM_RISCV_ISA_EXT_MAX; i++)
> > +               __vcpu_get_reg(vcpu, RISCV_ISA_EXT_REG(i), &isa_ext_state[i]);
> >
> >         /*
> >          * Disable all extensions which were enabled by default
> >          * if they were available in the risc-v host.
> >          */
> > -       for (int i = 0; i < KVM_RISCV_ISA_EXT_MAX; i++)
> > -               __vcpu_set_reg(vcpu, RISCV_ISA_EXT_REG(i), 0);
> > +       for (int i = 0; i < KVM_RISCV_ISA_EXT_MAX; i++) {
> > +               rc = __vcpu_set_reg(vcpu, RISCV_ISA_EXT_REG(i), 0);
> > +               if (rc && isa_ext_state[i])
> > +                       isa_ext_cant_disable[i] = true;
> > +       }
> >
> >         for_each_sublist(c, s) {
> >                 if (!s->feature)
> > --
> > 2.34.1
> >
>
> Otherwise, LGTM.
>
> Reviewed-by: Atish Patra <atishp@xxxxxxxxxxxx>
>
> --
> Regards,
> Atish

Regards,
Anup