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

[Borislav Petkov]

On Thu, Sep 29, 2022 at 03:29:02PM -0700, Rick Edgecombe wrote:
> Both XSAVE state components are supervisor states, even the state
> controlling user-mode operation. This is a departure from earlier features
> like protection keys where the PKRU state a normal user (non-supervisor)
^^^^^

A verb is missing in that sentence.

> +	"x87 floating point registers"			,
> +	"SSE registers"					,
> +	"AVX registers"					,
> +	"MPX bounds registers"				,
> +	"MPX CSR"					,
> +	"AVX-512 opmask"				,
> +	"AVX-512 Hi256"					,
> +	"AVX-512 ZMM_Hi256"				,
> +	"Processor Trace (unused)"			,
> +	"Protection Keys User registers"		,
> +	"PASID state"					,
> +	"Control-flow User registers"			,
> +	"Control-flow Kernel registers (unused)"	,
> +	"unknown xstate feature"			,
> +	"unknown xstate feature"			,
> +	"unknown xstate feature"			,
> +	"unknown xstate feature"			,
> +	"AMX Tile config"				,
> +	"AMX Tile data"					,
> +	"unknown xstate feature"			,

What Kees said. :)

> +	XCHECK_SZ(&chked, sz, nr, XFEATURE_YMM,       struct ymmh_struct);
> +	XCHECK_SZ(&chked, sz, nr, XFEATURE_BNDREGS,   struct mpx_bndreg_state);
> +	XCHECK_SZ(&chked, sz, nr, XFEATURE_BNDCSR,    struct mpx_bndcsr_state);
> +	XCHECK_SZ(&chked, sz, nr, XFEATURE_OPMASK,    struct avx_512_opmask_state);
> +	XCHECK_SZ(&chked, sz, nr, XFEATURE_ZMM_Hi256, struct avx_512_zmm_uppers_state);
> +	XCHECK_SZ(&chked, sz, nr, XFEATURE_Hi16_ZMM,  struct avx_512_hi16_state);
> +	XCHECK_SZ(&chked, sz, nr, XFEATURE_PKRU,      struct pkru_state);
> +	XCHECK_SZ(&chked, sz, nr, XFEATURE_PASID,     struct ia32_pasid_state);
> +	XCHECK_SZ(&chked, sz, nr, XFEATURE_XTILE_CFG, struct xtile_cfg);
> +	XCHECK_SZ(&chked, sz, nr, XFEATURE_CET_USER,  struct cet_user_state);

That looks silly. I wonder if you could do:

	switch (nr) {
	case XFEATURE_YMM:	XCHECK_SZ(sz, XFEATURE_YMM, struct ymmh_struct);	  return;
	case XFEATURE_BNDREGS:	XCHECK_SZ(sz, XFEATURE_BNDREGS, struct mpx_bndreg_state); return;
	case ...
	...
	default:
		/* that falls into the WARN etc */

and then you get rid of the if check in the macro itself and leave the
macro be a dumb, unconditional one.

Hmmm.

-- 
Regards/Gruss,
    Boris.

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