linux-kernel - Re: [PATCH v2 05/39] x86/fpu/xstate: Introduce CET MSR and XSAVES supervisor states

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Date:   Mon, 17 Oct 2022 21:33:56 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
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Subject: Re: [PATCH v2 05/39] x86/fpu/xstate: Introduce CET MSR and XSAVES
 supervisor states

On Mon, Oct 17, 2022 at 06:57:13PM +0000, Edgecombe, Rick P wrote:
> Hmm yea. Another reason the actual define is passed in is that the
> macro want's to stringify the XFEATURE define in order to generate the 
> message like this:
> XFEATURE_YMM: struct is 123 bytes, cpu state is 456 bytes
> 
> The exact format of the message is probably not too critical though. If
> instead it used xfeature_names[], it could be:
> [AVX registers]: struct is 123 bytes, cpu state is 456 bytes

Bah, "registers", that made me look at the thing. Yeah, not sure if all
those "registers" strings even matter there.

[AVX]: struct is 123 bytes, cpu state is 456 bytes

looks good enough to me too. But WTH do I know.

> The full block looks like (like you had):
> switch (nr) {
> case XFEATURE_YMM:	  return XCHECK_SZ(sz, nr, struct ymmh_struct);
> case XFEATURE_BNDREGS:	  return XCHECK_SZ(sz, nr, struct
> mpx_bndreg_state);
> case XFEATURE_BNDCSR:	  return XCHECK_SZ(sz, nr, struct
> mpx_bndcsr_state);
> case XFEATURE_OPMASK:	  return XCHECK_SZ(sz, nr, struct
> avx_512_opmask_state);
> case XFEATURE_ZMM_Hi256:  return XCHECK_SZ(sz, nr, struct
> avx_512_zmm_uppers_state);
> case XFEATURE_Hi16_ZMM:	  return XCHECK_SZ(sz, nr, struct
> avx_512_hi16_state);
> case XFEATURE_PKRU: 	  return XCHECK_SZ(sz, nr, struct pkru_state);
> case XFEATURE_PASID: 	  return XCHECK_SZ(sz, nr, struct
> ia32_pasid_state);
> case XFEATURE_XTILE_CFG:  return XCHECK_SZ(sz, nr, struct xtile_cfg);
> case XFEATURE_CET_USER:	  return XCHECK_SZ(sz, nr, struct
> cet_user_state);
> case XFEATURE_XTILE_DATA: check_xtile_data_against_struct(sz); return
> true;
> default:
> 	WARN_ONCE(1, "no structure for xstate: %d\n", nr);
> 	XSTATE_WARN_ON(1);
> 	return false;
> }
> 
> I like how it fits the XFEATURE_XTILE_DATA check in with the rest.

Yap, nice and straight-forward pattern. :)

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette