Re: [PATCH 29/35] target/arm: Mark up VNCR offsets (offsets 0x100..0x160)

[Peter Maydell]

On Thu, 28 Dec 2023 at 00:42, Richard Henderson
<richard.henderson@linaro.org> wrote:
>
> On 12/18/23 22:32, Peter Maydell wrote:
> > Mark up the cpreginfo structs to indicate offsets for system
> > registers from VNCR_EL2, as defined in table D8-66 in rule R_CSRPQ in
> > the Arm ARM.  This commit covers offsets 0x100 to 0x160.
> >
> > Many (but not all) of the registers in this range have _EL12 aliases,
> > and the slot in memory is shared between the _EL12 version of the
> > register and the _EL1 version.  Where we programmatically generate
> > the regdef for the _EL12 register, arrange that its
> > nv2_redirect_offset is set up correctly to do this.
> >
> > Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> > ---
> >   target/arm/debug_helper.c |  1 +
> >   target/arm/helper.c       | 22 ++++++++++++++++++++++
> >   2 files changed, 23 insertions(+)
>
> Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
>
> > +        /*
> > +         * If the _EL1 register is redirected to memory by FEAT_NV2,
> > +         * then it shares the offset with the _EL12 register,
> > +         * and which one is redirected depends on HCR_EL2.NV1.
> > +         */
> > +        if (new_reg->nv2_redirect_offset) {
> > +            assert(new_reg->nv2_redirect_offset & NV2_REDIR_NV1);
> > +            new_reg->nv2_redirect_offset &= ~NV2_REDIR_NV1;
> > +            new_reg->nv2_redirect_offset |= NV2_REDIR_NO_NV1;
> > +        }
>
> Could use xor to flip both bits at once.

Could do, but explicit clear-then-set seems a bit more
readable to me, and since this is only happening once at
startup there's no efficiency concern here.

thanks
-- PMM