Re: [PATCH v3 1/4] KVM: arm64: Apply the fine-grained UNDEFs without FEAT_FGT

[Fuad Tabba]

On Tue, 29 Sept 2026 at 15:54, Wei-Lin Chang <weilin.chang@xxxxxxx> wrote:
[...]
> This reads a bit mechanical to me, can I suggest:
>
> ```
> FGUs don't actually require hardware support, so don't gate fgt trap
> config insertion on FGT. This is the only action required to allow FGUs
> always, as kvm_calculate_traps() already computes the FGU bits with or
> without FEAT_FGT.
>
> This also fixes a spurious WARN when a TLBI OS is run on a guest in vEL1
> without FEAT_TLBIOS on non FEAT_FGT hardware. In this configuration the
> course-grained HCR_EL2.TTLBOS trap reaches the handler handle_tlbi_el1(),
> which expects an EL1 TLBI only from vEL2. With FGUs enabled the UNDEF
> will be injected without needing the specific handler.
> ```

I cannot write commit messages! :) Thanks for the suggestion and the
review. I'll reword if I respin.

Cheers,
/fuad