Re: [PATCH 09/35] target/arm: Record correct opcode fields in cpreg for E2H aliases

[Richard Henderson <richard.henderson@linaro.org>]

On 12/18/23 22:32, Peter Maydell wrote:
> For FEAT_VHE, we define a set of register aliases, so that for instance:
>   * the SCTLR_EL1 either accesses the real SCTLR_EL1, or (if E2H is 1)
>     SCTLR_EL2
>   * a new SCTLR_EL12 register accesses SCTLR_EL1 if E2H is 1
> 
> However when we create the 'new_reg' cpreg struct for the SCTLR_EL12
> register, we duplicate the information in the SCTLR_EL1 cpreg, which
> means the opcode fields are those of SCTLR_EL1, not SCTLR_EL12.  This
> is a problem for code which looks at the cpreg opcode fields to
> determine behaviour (e.g.  in access_check_cp_reg()). In practice
> the current checks we do there don't intersect with the *_EL12
> registers, but for FEAT_NV this will become a problem.
> 
> Write the correct values from the encoding into the new_reg struct.
> This restores the invariant that the cpreg that you get back
> from the hashtable has opcode fields that match the key you used
> to retrieve it.
> 
> When we call the readfn or writefn for the target register, we
> pass it the cpreg struct for that target register, not the one
> for the alias, in case the readfn/writefn want to look at the
> opcode fields to determine behaviour. This means we need to
> interpose custom read/writefns for the e12 aliases.
> 
> Signed-off-by: Peter Maydell<peter.maydell@linaro.org>
> ---
>   target/arm/helper.c | 35 +++++++++++++++++++++++++++++++++++
>   1 file changed, 35 insertions(+)

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

r~