[RFC PATCH v3 12/29] KVM: arm64: Make ID_DFR1_EL1 writable

[Reiji Watanabe]

Hi Eric,

On Thu, Nov 25, 2021 at 12:30 PM Eric Auger <eauger at redhat.com> wrote:
>
> Hi Reiji,
>
> On 11/17/21 7:43 AM, Reiji Watanabe wrote:
> > This patch adds id_reg_info for ID_DFR1_EL1 to make it writable
> > by userspace.
> >
> > Signed-off-by: Reiji Watanabe <reijiw at google.com>
> > ---
> >  arch/arm64/kvm/sys_regs.c | 6 ++++++
> >  1 file changed, 6 insertions(+)
> >
> > diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
> > index fbd335ac5e6b..dda7001959f6 100644
> > --- a/arch/arm64/kvm/sys_regs.c
> > +++ b/arch/arm64/kvm/sys_regs.c
> > @@ -859,6 +859,11 @@ static struct id_reg_info id_dfr0_el1_info = {
> >       .get_reset_val = get_reset_id_dfr0_el1,
> >  };
> >
> > +static struct id_reg_info id_dfr1_el1_info = {
> > +     .sys_reg = SYS_ID_DFR1_EL1,
> > +     .ftr_check_types = S_FCT(ID_DFR1_MTPMU_SHIFT, FCT_LOWER_SAFE),
> what about the 0xF value which indicates the MTPMU is not implemented?

The field is treated as a signed field.
So, 0xf(== -1) is handled correctly.
(Does it answer your question?)

Thanks,
Reiji

>
> Eric
> > +};
> > +
> >  /*
> >   * An ID register that needs special handling to control the value for the
> >   * guest must have its own id_reg_info in id_reg_info_table.
> > @@ -869,6 +874,7 @@ static struct id_reg_info id_dfr0_el1_info = {
> >  #define      GET_ID_REG_INFO(id)     (id_reg_info_table[IDREG_IDX(id)])
> >  static struct id_reg_info *id_reg_info_table[KVM_ARM_ID_REG_MAX_NUM] = {
> >       [IDREG_IDX(SYS_ID_DFR0_EL1)] = &id_dfr0_el1_info,
> > +     [IDREG_IDX(SYS_ID_DFR1_EL1)] = &id_dfr1_el1_info,
> >       [IDREG_IDX(SYS_ID_AA64PFR0_EL1)] = &id_aa64pfr0_el1_info,
> >       [IDREG_IDX(SYS_ID_AA64PFR1_EL1)] = &id_aa64pfr1_el1_info,
> >       [IDREG_IDX(SYS_ID_AA64DFR0_EL1)] = &id_aa64dfr0_el1_info,
> >
>