Re: [PATCH v4 07/39] x86: Add user control-protection fault handler

On Wed, Dec 21, 2022 at 09:42:50PM +0000, Edgecombe, Rick P wrote:

Oh, you mean the whole Kconfig thing. Yea, I mean I see the point about
typical configs. But at least CONFIG_X86_CET seems consistent with
CONFIG_INTEL_TDX_GUEST, CONFIG_IOMMU_SVA, etc.

What about moving it out of traps.c to a cet.c, like
exc_vmm_communication for CONFIG_AMD_MEM_ENCRT? Then the inclusion
logic lives in the build files, instead of an ifdef.

Yeah, that definitely sounds cleaner. Another example would be the #MC handler
being in mce code and not in traps.c.

So yeah, the reason why I'm even mentioning this is that I get an allergic
reaction when I see unwieldy ifdeffery in one screen worth of code. But this is
just me. :)

One aspect that has come up a couple of times, is how closely related
all these CET features are (or aren't). Shadow stack and IBT are mostly
separate, but do share an xfeature and an exception type. Similarly for
supervisor and user mode support for either of the CET features. So
maybe that is what is unusual here. There are some aspects that make
them look like separate features, which leads people to think they
should be separate in the code. But actually separating them leads to
excess ifdefery.

Yeah, I think you solved that correctly by having the common X86_CET symbol
selected by the two.

Thx.

-- 
Regards/Gruss,
    Boris.

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