Re: [PATCH v7 4/6] target/arm: Add FEAT_TCR2

[Pierrick Bouvier <pierrick.bouvier@linaro.org>]

On 7/14/25 5:58 AM, Richard Henderson wrote:
> On 7/14/25 00:21, Pierrick Bouvier wrote:
>> On 7/13/25 2:59 PM, Richard Henderson wrote:
>>> On 7/11/25 08:08, Gustavo Romero wrote:
>>>> Add FEAT_TCR2, which introduces the TCR2_EL1 and TCR2_EL2 registers.
>>>> These registers are extensions of the TCR_ELx registers and provide
>>>> top-level control of the EL10 and EL20 translation regimes.
>>>>
>>>> Since the bits in these registers depend on other CPU features, and only
>>>> FEAT_MEC is supported at the moment, the FEAT_TCR2 only implements the
>>>> AMEC bits for now.
>>>>
>>>> Signed-off-by: Gustavo Romero <gustavo.romero@linaro.org>
>>> This causes a regression in tests/functional/test_aarch64_device_passthrough.py, by
>>> continually trapping on an access to TCR2_EL1 while the HCRX_EL2 enable bit is not set.
>>>
>>> Unlike the similar SCTRL2 failure, it's not 100% clear to me how the guest and nested
>>> guest kernels are related.  But it is clear that the outer kernel does not does not
>>> support TCR2_EL1 (and also doesn't manipulate ID_AA64MMFR3_EL1 to hide FEAT_TCR2), but the
>>> nested guest kernel does support TCR2_EL1.
>>>
>>
>> The same kernel is used for host and guest.
>> Maybe it's related to kvm support?
> 
> Oops, no, the patch fails to enable HCRX_TCR2EN in hcrx_write or SCR_TCR2EN in scr_write.
> The same is true for the previous patch with HCRX_SCTLR2EN and SCR_SCTLR2EN.
> 

Thanks for the investigation. Indeed, building TF-A with 
ENABLE_FEAT_TCR2 and ENABLE_FEAT_SCTRL2 didn't change anything.

It's possible that it's still needed to update test images though, so 
I'll try when Gustavo will post v8.

Thanks,
Pierrick

> 
> r~