Re: [PATCH v1 2/3] arm64: sysreg: Add TCR_EL2 to sysreg infrastructure

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] Declarative update to TCR_EL2 regenerates the TCR_EL2_RES1 aggregate mask which is consumed by C initialization, requiring confirmation of robustness to future value changes.
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commit 522a184d95be9c0f88cc6fb418668546ef83e3e4
Author: Wei-Lin Chang <weilin.chang@arm.com>

    arm64: sysreg: Add TCR_EL2 to sysreg infrastructure
    
    Convert TCR_EL2 to the sysreg infrastructure with data extracted from
    Registers.json of the BSD licenced AARCHMRS
    (AARCHMRS_OPENSOURCE_A_profile_FAT-2026-06).

> diff --git a/arch/arm64/tools/sysreg b/arch/arm64/tools/sysreg
> index 94bf065c8ac71..8d89f34580bac 100644
> --- a/arch/arm64/tools/sysreg
> +++ b/arch/arm64/tools/sysreg
[ ... ]
> +Sysreg	TCR_EL2		3	4	2	0	2
[ ... ]
> +Field	33	MTX
> +Field	32	DS
> +Res1	31
> +Field	30	TCMA
> +Field	29	TBID
> +Field	28	HWU62
> +Field	27	HWU61
> +Field	26	HWU60
> +Field	25	HWU59
> +Field	24	HPD
> +Res1	23
> +Field	22	HD

[Severity: Medium]
This isn't a bug, but this declarative update regenerates the TCR_EL2_RES1
aggregate mask. Are the C initialization consumers of this mask robust to its
value silently changing if a future .sysreg patch adds or removes a Res1 bit?

For example, the generated mask is OR'd into the initial EL2 register value:

arch/arm64/kvm/arm.c:cpu_prepare_hyp_mode() {
    ...
    tcr |= TCR_EL2_RES1 | FIELD_PREP(TCR_EL2_PS_MASK, ips);
    ...
}

It is also used to initialize the guest emulation reset state in:

arch/arm64/kvm/sys_regs.c:sys_reg_descs[] = {
    ...
    EL2_REG(TCR_EL2, access_rw, reset_val, TCR_EL2_RES1),
    ...
}

Because the generator's contract is to reflect global architectural truth, a
future edit that reclassifies a bit as Res1 will silently change the value of
TCR_EL2_RES1 without triggering a compiler or CI warning. Could you confirm
that these consumers do not rely on the previous static semantic value of the
mask?

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Sashiko AI review · https://sashiko.dev/#/patchset/20260909222015.3046432-1-weilin.chang@arm.com?part=2