Re: [PATCH] target/arm: arm_pamax() no longer needs to do feature propagation

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

On 1/10/24 01:38, Peter Maydell wrote:
> In arm_pamax(), we need to cope with the virt board calling this
> function on a CPU object which has been inited but not realize.
> We used to do propagation of feature-flag implications (such as
> "V7VE implies LPAE") at realize, so we have some code in arm_pamax()
> which manually checks for both V7VE and LPAE feature flags.
> 
> In commit b8f7959f28c4f36 we moved the feature propagation for
> almost all features from realize to post-init. That means that
> now when the virt board calls arm_pamax(), the feature propagation
> has been done. So we can drop the manual propagation handling
> and check only for the feature we actually care about, which
> is ARM_FEATURE_LPAE.
> 
> Retain the comment that the virt board is calling this function
> with a not completely realized CPU object, because that is a
> potential beartrap for later changes which is worth calling out.
> 
> (Note that b8f7959f28c4f36 actually fixed a bug in the arm_pamax()
> handling: arm_pamax() was missing a check for ARM_FEATURE_V8, so it
> incorrectly thought that the qemu-system-arm 'max' CPU did not have
> LPAE and turned off 'highmem' support in the virt board.  Following
> b8f7959f28c4f36 qemu-system-arm 'max' is treated the same as
> 'cortex-a15' and other v7 LPAE CPUs, because the generic feature
> propagation code does correctly propagate V8 -> V7VE -> LPAE.)
> 
> Signed-off-by: Peter Maydell<peter.maydell@linaro.org>
> ---
>   target/arm/ptw.c | 14 ++++++--------
>   1 file changed, 6 insertions(+), 8 deletions(-)

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

r~