[PATCH 2/2] RISC-V: KVM: Restrict the extensions that can be disabled

[Anup Patel]

On Wed, Apr 20, 2022 at 1:13 PM Atish Patra <atishp at atishpatra.org> wrote:
>
> On Tue, Apr 19, 2022 at 6:33 PM Atish Patra <atishp at rivosinc.com> wrote:
> >
> > Currently, the config reg register allows to disable all allowed
> > single letter ISA extensions. It shouldn't be the case as vmm
> > shouldn't be able disable base extensions (imac).
>
> /s/able/able to/
>
> > These extensions should always be enabled as long as they are enabled
> > in the host ISA.
> >
> > Signed-off-by: Atish Patra <atishp at rivosinc.com>
> > ---
> >  arch/riscv/kvm/vcpu.c | 21 +++++++++++++--------
> >  1 file changed, 13 insertions(+), 8 deletions(-)
> >
> > diff --git a/arch/riscv/kvm/vcpu.c b/arch/riscv/kvm/vcpu.c
> > index 2e25a7b83a1b..14dd801651e5 100644
> > --- a/arch/riscv/kvm/vcpu.c
> > +++ b/arch/riscv/kvm/vcpu.c
> > @@ -38,12 +38,16 @@ const struct kvm_stats_header kvm_vcpu_stats_header = {
> >                        sizeof(kvm_vcpu_stats_desc),
> >  };
> >
> > -#define KVM_RISCV_ISA_ALLOWED  (riscv_isa_extension_mask(a) | \
> > -                                riscv_isa_extension_mask(c) | \
> > -                                riscv_isa_extension_mask(d) | \
> > -                                riscv_isa_extension_mask(f) | \
> > -                                riscv_isa_extension_mask(i) | \
> > -                                riscv_isa_extension_mask(m))
> > +#define KVM_RISCV_ISA_DISABLE_ALLOWED  (riscv_isa_extension_mask(d) | \
> > +                                       riscv_isa_extension_mask(f))
> > +
> > +#define KVM_RISCV_ISA_DISABLE_NOT_ALLOWED      (riscv_isa_extension_mask(a) | \
> > +                                               riscv_isa_extension_mask(c) | \
> > +                                               riscv_isa_extension_mask(i) | \
> > +                                               riscv_isa_extension_mask(m))
> > +
> > +#define KVM_RISCV_ISA_ALLOWED (KVM_RISCV_ISA_DISABLE_ALLOWED | \
> > +                              KVM_RISCV_ISA_DISABLE_NOT_ALLOWED)
> >
> >  static void kvm_riscv_reset_vcpu(struct kvm_vcpu *vcpu)
> >  {
> > @@ -217,9 +221,10 @@ static int kvm_riscv_vcpu_set_reg_config(struct kvm_vcpu *vcpu,
> >         switch (reg_num) {
> >         case KVM_REG_RISCV_CONFIG_REG(isa):
> >                 if (!vcpu->arch.ran_atleast_once) {
> > -                       vcpu->arch.isa = reg_val;
> > +                       /* Ignore the disable request for these extensions */
> > +                       vcpu->arch.isa = reg_val | KVM_RISCV_ISA_DISABLE_NOT_ALLOWED;
> >                         vcpu->arch.isa &= riscv_isa_extension_base(NULL);
> > -                       vcpu->arch.isa &= KVM_RISCV_ISA_ALLOWED;
> > +                       vcpu->arch.isa &= KVM_RISCV_ISA_DISABLE_ALLOWED;
> >                         kvm_riscv_vcpu_fp_reset(vcpu);
> >                 } else {
> >                         return -EOPNOTSUPP;
> > --
> > 2.25.1
> >
>
> Sorry. I forgot to add the fixes tag.
>
> Fixes: 92ad82002c39 (RISC-V: KVM: Implement
> KVM_GET_ONE_REG/KVM_SET_ONE_REG ioctls)

I have queued this for fixes.

Thanks,
Anup

>
> --
> Regards,
> Atish
>
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